What Should my AC Pressure Be?


ac pressureKnowing what the pressures are in the air conditioning system in your car can tell you almost all you need to know about how your system is functioning.  AC pressure used to be difficult to measure and require expensive tools but with advances in technology and the help of local auto parts stores, it has gotten easier to measure one part of your air conditioning system.

AC refill cans are readily available at your local auto parts stores and even at many larger stores.  Many of these refill cans come complete with a pressure gauge to help you discover a little bit of what’s going on in your system and to help you guess at how much refrigerant to dispense.  These gauges are relatively accurate and an inexpensive way to measure the low side pressure in your system.

Unfortunately, the low side pressure is just one piece of the puzzle.  Your air conditioning system is split in half when it comes to pressure.  Your air conditioning system holds a very high pressure between your AC compressor and condenser up expansion valve, and a relatively low pressure after the expansion valve and evaporator and back to the inlet of the compressor.

The can of refrigerant you purchased from the auto parts store is pressurized so it can push the new refrigerant into the system.  To make sure you get as much refrigerant out of the can and into your system, you connect it to the lower pressure side of the system so it is the low side pressure that you see measured on the gauge on your refill can.

To measure the pressure in the high-pressure side of your system, you need a little fancier piece of equipment.  The pressures in the high-pressure side of your system are so high that it requires special hoses and connections along with a special gauge to contain the pressure and ensure you don’t release any of the refrigerant to the atmosphere.  The best way to measure the high-pressure side of your system is to get the proper tools for a local auto parts store.  This set of A/C Manifold Gauges would work great!

Now that you’ve got a safe and reliable way to measure your AC pressure, you need to know what you’re looking for.  Pressures can vary from car to car based on the system and the pressure in your system will also vary with the ambient temperature.  The warmer it is outside, the higher the pressure will be.  For a general reference, you can check out this chart of R-134a system pressures.

If you find you’ve got a low pressure on the low side of your system, then it’s most likely that you’ve got a leak as that is a common problem in automobile air conditioning systems.  A low pressure on the low side could also indicate a clog somewhere in your system.  If you find a higher than usual low side pressure it usually is an indication of a failed compressor, but it’s also possible that your system is simply overfilled if you’ve recently added refrigerant.

On the high-pressure side of the system, a low pressure can also indicate that you’ve got a low refrigerant level or if the pressure is close to the same as it is on the low-pressure side it can confirm you’re having compressor issues.  A higher pressure here can again indicate your system is overfilled if you’ve recently serviced it, but usually, it is an indication of a clog in the system.

Most problems with your air conditioning system will require a vacuum, repair, and refill of the system.  Leaks, on the other hand, are problems solved simply by adding Red Angel A/C Stop leak & Conditioner through the low-pressure port in your system!

For more information on Red Angel A/C Stop Leak & Conditioner including how it works and directions for use, click on the banner below!
Red Angel AC Stop Leak & Conditioner





You can also find Red Angel A/C Stop Leak & Conditioner at any of our partnering auto parts stores like:

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65 responses to "What Should my AC Pressure Be?"


  1. Louis on June 20, 2017 at 10:39 pm

    I change the A/C canister, cause the valve to fill, was broken, so I bought a brand new one. I installed it, and I saw on internet I have to add oil in it before to fill it with refrigerant, but which oil I have to add, and how many ??? My car is a 1997 chevrolet Camaro RS 3.8 litre. Thank you !

    • BlueDevil Pro on June 21, 2017 at 4:05 pm


      You would need 26 ounces of PAG 150 for your Chevrolet Camaro 6 cylinder. Feel free to contact our technical support line at 888-863-0426 with any other questions.

      Thank you!


    • Andrii on May 18, 2020 at 12:42 am

      Acura csx 2007 ac is working for 20 minutes and stops blowing up cold air, cluch on compressor is not engaging any more but fans on radiator are working non stop. What the problem is? The system is charged with frion

      • BlueDevil Pro on May 18, 2020 at 10:49 am


        Thank you for asking about your Acura CSX. If the a/c compressor clutch isn’t engaging, the issue could be due to a blown fuse or the clutch itself having gone bad. The wiring to the clutch coil could also be starting to short out, explaining why it would blow cold for 20 minutes and then stop. Check to make sure there are no blown fuses and that there are no wiring issues and then re-assess the situation.

        Hope this helps!


      • Andrew on June 29, 2021 at 9:24 pm

        Hi I have a 2011 Mercury Milan premier 3.0 it takes 22 oz of r134a what is that on PSI low pressure side

        • BlueDevil Pro on June 30, 2021 at 8:36 am


          Thank you for asking about your Mercury Milan. The low side should be reading at about 30 PSI. If the PSI is much higher or lower than this, it may indicate a problem within the system.

          Thank you!


  2. Sandy on August 11, 2017 at 1:50 am

    I have a problem with the a.c…
    A couple of weeks ago…
    My truck (2000 Chevy Silverado 1500) stop cooling off…
    Started blowing cold air but it wasn’t enough cooling like before… So, we tough that may be the gas (idk the correct name to called.. sorry) was finished, and yesterday I bought a a/c refrigerant I didn’t know how to do it, so, I asked for help to my uncle, and he helped me.. so on the way back of his house to mine ( like 1 or 2 mins away) was cooling perfect…
    Now this noon I tough that May b will be perfect… But my surprise that it was blowing hot air when I turn on the a/c..
    Now it’s not cold like before… At least before I was available to close the windows and feel a little bit of cold air.. but not now…
    So, I went back to my uncle house and telling him about the problem, and he told me that may be was that needs oil for the AC… Ok then I went to buy another refrigerant but now with oil or conditioner… and he filled out… But it’s not working… Still blowing hot air… and he told me that the air compressor it’s not working, so I have to change it!?!!! and while I was driving today (without the AC on… Super hot weather) I listened a wear noise like it was like a Lawnmower not loud but I can hear it while I was driving…
    I’ll appreciate your help!!!

    • BD Auto Pro on August 14, 2017 at 6:58 pm


      Thanks for your question about your 2000 Chevy Silverado. Based on your description of the loss of cooling, it sounds like you’ve got a leak in your system letting the new refrigerant you put in escape again. Our recommendation would be to use Red Angel A/C Stop Leak and Conditioner (available here: http://store.gobdp.com/a-c-stop-leak-aerosol-00222/) to seal the leak, then add refrigerant until your compressor starts running again.

      Thanks again for your question!
      -BD Auto Pro

  3. Chris Thomas on September 17, 2017 at 10:50 am

    I replaced my account compressor , acculalator and expansion valve, the oil chart said I needed 14 oz of oil and 58 oz of freon. I put 11 oz of oil and 58 oz of freon in it I ran my truck for awhile air blows cold but my high side pressure got to 450 low side was around 60. What’s wrong? Oh it’s a 2006 Ford expedition

    • BD Auto Pro on September 18, 2017 at 8:01 pm


      Thanks for your question about your air conditioning. Unless it was extremely warm outside, those pressures do sound to be a bit high. You might try calling Ford to find out what the pressures in your system should be just to make sure they are higher than normal. This could have happened if you didn’t fully evacuate your air conditioning system before you installed the new refrigerant and oil or it could be an indication that you’ve got some clogs somewhere in your system increasing pressure.

      Thanks again for your question!
      -BD Auto Pro

  4. Kapil on May 22, 2018 at 8:33 pm

    I have 2007 sentra and it stopped blowing cold air this summer. I checked the low pressure and it always shows 100 psi even if the ac is switched on or off. Could it be a faulty gauge. I checked the same thing on my altima and it shows same air pressure. I am thinking it is definitely a faulty gauge. But wanted to check with you.
    I just checked pressure in my altima’s ac system after starting it and it is showing 25psi. This means gauge is working fine. Can you please help me why pressure in my sentra is 100psi and there is no cold air

    • BD Auto Pro on May 24, 2018 at 8:41 am


      Thanks for your question about your Nissan Sentra. When your AC compressor isn’t running, the pressure in your system equalizes between the high and low side. What that pressure should be depends on the design of your system and the temperature outside when you take the measurement, but 100 psi with the compressor off may be just fine. When the compressor turns on it should lower the pressure on the low side of your system and that pressure again is dependant on ambient temperature and other factors. If the pressure isn’t lowering in your system with the AC switched on, then either your compressor isn’t running, or it has an internal failure.

      Thanks again for your question!
      -BD Auto Pro

      • Elijahhannigan on September 19, 2018 at 4:51 pm

        Honda civic head pressure too high

        • BlueDevil Pro on September 20, 2018 at 9:27 am


          The most common cause for high compressor head pressure is clogging or contamination in one of the refrigeration lines. This can be caused by a number of different factors such as blocked air flow across the cooling coil, debris or water contamination, even high ambient temperatures. We recommend bringing the vehicle to an A/C specialist for a proper diagnosis.

          Thank you!


  5. Joey Cortelli on May 29, 2018 at 8:22 am

    I have a 2014 Nissan Altima. My mystery is as follows: My AC cools off ice cold while it is 80F or below but it blows not hot air but neutral air when it’s over 90F. I followed some DIY tips and assumed it was low on freon so I bought a AC Pro 20 oz can with a gauge on it. First measured the L pressure with the gauge on the canister and it showed overcharged before putting anything in it. I assumed the gauge may be a faulty one so I put all the freon in. Then I realized it stopped the AC blowing any cool air even when the temp waa 75F at night. I read some more DIY tips and decided to discharge and let some pressure and freon out. I did let out quiet a bit. However the gauge always read on the red mark. But the AC started cooling off again like it was before; meaning cooling off when outside temp is 85F or below and blowing neutral air when it is over 80F. Tonight it was 80F and then dropped to 75F at night and it was blowing ice cold air. I checked the pressure at 1am while it was blowing cold air. It showed in the middle of the green mark. Today it will be 92F and I know it will blow neutral air like it has been past 4 days. Since it’s cooling off satisfactorily at nights or when the ambient temperature is 80 or below, can I override the compressor issue, the leak issue and possible clog issue? Or What might be causing my AC not to cool when it’s 90+ outside but work when it’s 80 or below outside. What may be wrong? Thanks in advance

    • BD Auto Pro on May 31, 2018 at 9:15 am


      Thanks for your question about your 2014 Nissan Altima. The most common causes of the problem you’re having are either an overfilled system or a clog in your system. In either of the situations, when the ambient temperature is high, it causes a higher pressure in your system and could be tripping it off on overpressure. You wouldn’t want to override this as it is a safety feature for your air conditioning system. Since you’ve now added and removed refrigerant, the only way to make sure your system isn’t overfilled would be to have the system completely evacuated then have the correct weight of refrigerant added. To check for a clog you would need to check the system high pressure when it was blowing cold air as well as when it wasn’t working.

      Thanks again for your question!
      -BD Auto Pro

    • George Waszczuk on June 1, 2019 at 5:19 pm




  6. Nick on May 29, 2018 at 7:57 pm

    Hi, i have a 2014 passat. The pressure readings are as follows:
    LP side
    Ac off: 115psi
    Ac on: it starts with 80 psi and sometimes goes down to 35 and blows cold air. It may not make sense but when the outside temp i high 35 Celsius it blows cold air. When the temp goes down 27 or so Celsius blows hot and veey rare blows cold air. So with the ac on it fluctuates feom 80 to 35psi. Any idea???

    • BD Auto Pro on May 31, 2018 at 9:18 am


      Thanks for your question about your 2014 Passat. The pressures you are seeing in your system could be within the normal operating range. Pressures in your air conditioning system will vary significantly with as ambient temperature varies so those could also be high or low depending on what the temperature was when you made the measurements. Since your system seems to work fine when it’s very warm out it could be that your system is a little low on refrigerant, but the symptoms you’re having could also be due to a clog which would require measuring the system high side pressure as well.

      Thanks again for your question!
      -BD Auto Pro

    • Lane on June 11, 2021 at 3:13 pm

      Slowly can in the system contaminate evacuate the system whole vacuum with the motor stopped put some free on in it bleed the line put some free on in it start the motor feel it 27 on the low takes a long time to fill it up don’t be in a hurry short bursts turn you can sideways and Shake and little bit once in awhile will make it fil faster got air which is water it is a contaminate it has to be a vacuum pulled on it when the motor is stopped believe the line then you put a little bit in it before you start the truck then you can continue filling your vehicle
      Slow leak is causing the contaminant

  7. Que on June 5, 2018 at 8:02 pm

    I have a 2000 GMC Aerotech passenger bus. It has 2 ac units running off of 1compressor and the Freon evaporated after 9 years of sitting. The tag calls for 4lbs and 8oz of refrigerant to feed both units during simultaneous running. I added a can and the compressor kicked on but was hot. Added another can and it started to chill. Looked at the pressure and it was at 40lbs. Added a 3rd can and it was at 50lbs. It became cooler at that point, but not cold.

    Do commercial vehicle units require more pressure than your personal vehicles? I don’t want to add another can to get it cold and it messes something up. Mind you, the ambient temp was 93 degrees and my gauge was at the 85+ temp reading.

    • BD Auto Pro on June 6, 2018 at 8:48 am


      Thanks for your question about your 2000 GMC Aerotech bus. The operating pressures of an air conditioning system are determined by the type of refrigerant used not the size or configuration of the system. To get your system operating at top efficiency you need to first evacuate the system, then add the refrigerant. If there is a leak allowing the refrigerant to escape, it also allowed air to get in. Having air in your system with the refrigerant will reduce the efficiency of the system and change the pressures. We recommend getting the system evacuated then adding refrigerant by weight.

      Thanks again for your question!
      -BD Auto Pro

  8. Carlos on July 16, 2018 at 7:34 pm

    I have a 2007 Kia Sportage that blows warm air when at a stop light or drive through. However, if I put it in park or neutral and throttle the rpm’s up to 2500-3000, it starts cooling again. When idle, my low side reads about 32psi and high side reads about 220psi. I have only checked it multiple times within the last two weeks when ambient temperature is near 100 Fahrenheit. Any ideas why it is doing this?

    • BD Auto Pro on July 19, 2018 at 9:10 am


      Thanks for your question about your 2007 Kia Sportage. Both of those pressure readings seem a little low for an ambient temperature of 100 degrees. You can try using this chart to see what pressures should be based on outside temperatures. It could be that your system is low on refrigerant since both the high and low side pressures are low. Also, it’s possible that your compressor is starting to get worn out since things work a little better when your engine is turning at a higher RPM but you would need to make sure you’ve got the right amount of refrigerant in the system before you could check for that.

      Thanks again for your question!
      -BD Auto Pro

  9. James on July 17, 2018 at 3:59 am

    Got a 98 S10 my high pressure line is hot ..really hot .im in AZ and temps now are in the 105-110 range . She blows cold,air just wondering how hot is the high pressure line supposed to get ..can it be there is air in the system ..

    • BD Auto Pro on July 19, 2018 at 9:13 am


      Thanks for your question about your 1998 Chevy S10. The high-pressure line between the compressor and the condenser will get very hot, too hot to touch, under normal operating conditions. The compressor raises the pressure of the refrigerant to over 300 PSI and all the compression adds a lot of heat to the refrigerant so that is perfectly normal. There aren’t any specifications for temperatures of the refrigerant entering the condenser as long as the refrigerant is cooled to ambient temperature by the time it comes out, everything will work properly.

      Thanks again for your question!
      -BD Auto Pro

  10. Abhi on August 9, 2018 at 12:24 pm

    My 2007 Honda Civic was having cooling issues, so I bought a a/c refrigerant and topped it up. It came along with a pressure gauge for low port. I get very high readings when I have driven the car and low reading when the car is in shade or couple of hours. Which one is accurate?
    My AC problem had resolved for few days after I had topped it up, but now it starts blowing hot air after I have drive the car for few minutes. What maybe the problem here?

    Thanks in advance.

    • BD Auto Pro on August 11, 2018 at 10:30 am


      Thanks for your question about your 2007 Honda Civic. It sounds like you’ve got a slow leak in your air conditioning system since adding refrigerant helped it work for a few days. Use Red Angel A/C Stop Leak so seal the leak and keep your air conditioning system working properly. The low side pressure in your air conditioning system should drop down significantly when your engine is running and your AC compressor is cycling on. When the compressor shuts off or you turn your car off the pressures in the system will equalize between the high and low side so the low side pressure will read much higher.

      Thanks for your question!
      -BD Auto Pro

  11. Shail on September 16, 2018 at 1:09 pm

    Hi I have a Honda Brio and it met with a small accident which damaged the condenser needing a repair and then refilling of Cooling Gas. I had the AC pressure checked (Car engine running and pressure valves attached) and it stabilized around 32 in the ambient temperature of around 35 degree celcius. I wanted to understand in what is the desired AC pressure level for a Honda Brio car.

    • BlueDevil Pro on September 17, 2018 at 12:40 pm


      Thank you for asking about your Honda Brio. At 35 degrees Celsius, the low pressure gauge should read between 50-55 psi, and the high pressure gauge should read between 275-300 psi.

      Thank you!


  12. Andy Tollinger on September 23, 2018 at 11:51 am

    I have a 95 F150. Just replaced fan clutch, compressor, accumulator, and orifice. Added appropriate amount of PAG oil, pulled vaccum, and charged 134a. Everything is cooling however at idle I’m seeing my pressure climb sky high before the fan clutch engages. So far example when the truck is warming up and the fan clutch is not engaged (several minutes), if I turn the AC the High side climbs to approx 350-400 (high side pressure sensor turns off compressor after 430 I believe), and the low side can get up to approx 60 – 70. Once the thermal fan clutch senses the high temperature it engages, the ac gauges read approx 35 low, 190 high. The truck is cooling great. Is this normal operation for a truck with thermal fan clutch. I read that the pressure should not be this high?

    • BD Auto Pro on September 24, 2018 at 6:10 pm


      Thanks for your question about your 1995 Ford F150. The fan clutch you installed responds to increases in temperature and the demand of the air conditioning takes a long time to get heat to the fan clutch to get it to engage so it is definitely possible that is normal operation for your truck. Most new vehicles have electric fans in addition to the engine driven fan that come on when the compressor is cycling. You might consider installing an auxiliary electric fan that comes on when you turn your air conditioning on to keep the pressures lower in your system.

      Thanks again for your question!
      -BD Auto Pro

      • Andy Tollinger on September 25, 2018 at 9:23 pm

        Thanks for the input! I’ve been looking into aux fans but also thinking maybe the fan clutch is no good even though it’s new. Basically I’m wondering if it’s just not spinning fast enough even when not fully engaged. I may have a shop take a look just to make sure. I did have another question, when I replaced everything, the ac sticker on the truck says max oil is 11 fl oz and to use WSH-M1C231-B? When searching online this appears to be a Ford ac oil that is equivalent to PAG 46. What’s interesting is that all online databases that show ac oil levels specify that 95 F-150 takes 7 fl oz (95 Bronco says 11 fl oz). This is confusing, as that is a big difference. I checked some other 95 F150s stickers that also said 11 fl oz. Anyways if my sticker is only stating max oil and not nominal level should i have put 7 ounces instead? Would this extra oil cause this issue? Once again, when the fan clutch kicks on pressures are normal. Thanks Again!

        • BD Auto Pro on September 27, 2018 at 1:49 pm


          Thanks again for your question about your F150. It’s possible your truck required a different amount of oil. The sticker is almost always correct but to be absolutely sure you can try calling your local Ford dealership and giving the service department your VIN and asking them to look up the amount and type of AC oil that your system requires. The extra oil in your system may reduce it’s cooling capacity and may eventually clog the dryer which could increase pressures, but if that was the case it would always the pressure would always be too high. It’s also possible that the fan clutch you received is faulty say it may be worth having a mechanic check that out.

          Thanks again for your question!
          -BD Auto Pro

  13. Haider on April 21, 2019 at 1:33 am

    Hello sir,

    I need your guidance about my car’s AC issue, if you don’t mind. Currently my 2011 Kia Sportage (2.4) is blowing cool but not cold air. I changed the air cabin filter and cleaned the condenser (with hose water and cleaner) but it didn’t fix the problem. Also, radiator’s fan is working properly. I can see the compressor spinning when I turn on the AC. However, the compressor is not cycling on and off, all it does is spinning. Furthermore, the compressor’s pully spins freely when I turn it with my hand. When I hooked up my manifold gauges, the readings came as 72 psi on low side – 125 psi on high side while the ambient temperature was around 80. Where else should I look into? what course of action do you recommend next?

    Your help is much appreciated

    • BD Auto Pro on April 24, 2019 at 8:32 pm


      Thanks for your question about your 2011 Kia Sportage. Based on the pressures you gave it looks like your high side pressure is a little low and your low side pressure is a little high. That lack of temperature differential could be causing the air to be blowing a bit warm from your vents. This could indicate a clog somewhere in your system that is changing the pressures prematurely, but it is more likely an indication that your AC compressor is failing as it cannot adequately drop the low side pressure or compress the refrigerant to the needed high side pressure.

      Thanks again for your question!
      -BD Auto Pro

  14. Steven M Flowers on May 11, 2019 at 4:07 pm

    It is 70 degrees here in Texas and my AC pressure long my vehicle is running low side is 39 PSI and high side is 190 PSI. I drive a 2014 Chevy Silverado LT with a 5.3 L engine. My AC is blowing cold but I’m wondering if it is overcharged.

    • BlueDevil Pro on May 13, 2019 at 9:50 am


      Thank you for asking about your Chevy Silverado. Based on the pressure readings you’ve recorded, it’s possible the system is overcharged, although, the high side reading would usually be much higher than 190 PSI. You can check the system with a gauge and partially deplete the system if need be.

      Thank you!


  15. Brandon on May 23, 2019 at 11:20 am

    I have an ’03 Altima. When I try to check the low pressure there is no reading at all. Car/AC on, The needle doesn’t move. It is pointed straight down. Tried 2 different gauges…definitely has a seal, but no reading at all. Any idea what might cause this?

    • BlueDevil Pro on May 24, 2019 at 9:44 am


      Thank you for asking about your Nissan Altima. 0 PSI at the low side would indicate no refrigerant in the system, also that there is a leak somewhere. We recommend using the Red Angel A/C Refrigerant Stop Leak. As long as you are not losing more than about 1 lb of refrigerant a day, you would be a good candidate for the product. You would top the system off with refrigerant once you’ve completed adding Red Angel.

      Thank you!


  16. Nicholas Wanat on June 2, 2019 at 10:23 am

    My 94 buick lesabre A/C works fine however tere is a leak I can not find. Added dye still no luck, I’m thinking its the evaporator, when filled leaks over night, can blue devil fix this problem. What do you suggest. Thank you, Nick

    • BlueDevil Pro on June 3, 2019 at 11:08 am


      Thank you for asking about your Buick Lesabre. The Red Angel A/C Refrigerant Stop Leak would be able to treat a leaking evaporator. As long as you are not losing more than about a pound of refrigerant in a day, you would be a good candidate for the product.

      Thank you!


  17. Bryan Marsh on June 17, 2019 at 7:45 pm

    I have a 1972 Oldsmobile Cutlass that I upgraded to R134A. The compressor and air dryer filter have been changed. The thermo expansion valve was replaced with one designed for R134A. All O rings have been replaced. The fan motor has been replaced with two electric fans. The problem is at idle the discharge temp is 58 degrees at 75 degrees outside air temp. The low side pressure is 25 PSI and the high side is 210 PSI. What could be causing the higher discharge temps?

    • BD Auto Pro on June 18, 2019 at 12:56 am


      Thanks for your question about your 1972 Oldsmobile Cutlass. If you look up some pressure charts for R-134a, it sounds like your low side and high side pressure is a little high. High pressures in your system could be due to it being overfilled. Also, the lack of cooling could be due to a clog somewhere in your system which could also account for the pressures being incorrect. If the system wasn’t properly flushed when the new components were installed that could account for the clog. Since you also are working on an older vehicle you may also consider checking the evaporator coils to make sure they aren’t clogged or dirty reducing heat transfer.

      Thanks again for your question!
      -BD Auto Pro

  18. Anton on July 3, 2019 at 12:47 pm

    Ive read on many sites that AC systems looses 8-10% refrigerant per year. Whys that?

    My compressor doesnt engage. AC relät is clicking when i activate it manually through a scantool. AC magnetic clutch fuse is OK.
    Pressure on high side 970kPa. Read through scantool. Outside temperature about 18 degeee celsius.

    Last time the AC worked ive got a little ammoniak smell. Maybe dirty multifilter. Havent changed it for like 3-4 years

    Also when i have been turning my car off there have been a mechanical sound around the compressor. Something metal. Metal noise. Maybe compressor clutch dissengage?

    Volvo S40 1.8 2006.
    Never touched the AC since i bought it 2007. Have been working great all the time. But not the last 2 years. Cold byt not freezing Cold like before. Now it just blows warm air or outside temperature air. So i need to run with my windows open now.

    I hope there isnt a major leak somewhere. AC components are really expensive for my car. At least what i have seen.

    • BD Auto Pro on July 10, 2019 at 7:34 pm


      Thanks for your question about your Volvo S40. Your high side pressures sound about right based on the outside temperature assuming your compressor is engaging. If your compressor isn’t engaging and you have that reading then your system must be overfilled. Assuming the compressor is running and your high side and low side pressures are within range and you still aren’t getting cold air then our guess would be you’ve got a problem with your expansion valve or a clog in the evaporator or dryer.

      Thanks again for your question!
      -BD Auto Pro

  19. Joseph Hayes on July 30, 2019 at 9:09 pm

    Hello, I was just wondering if maybe you could help me. I have a 2010 Ford Fusion and have been trying to figure out why the compressor won’t kick on. The ACP Pressure sensor varies, sometimes it show 12 psi, 0 psi, i think right now it’s showing about 50 psi and won’t let the compressor kick on until it shows around 70 I think. At rest the voltage shows about 1.3v I think. I can kick the compressor on with scan tool and after the pressure goes up a little I can use the a/c buttons until I turn the car off or the pressure drops on the sensor. I replaced the switch with 2 different ones and it’s still doing the same thing. The manifold gauges show good on both the high and Low side.

    • BD Auto Pro on August 1, 2019 at 12:28 am


      Thanks for your question about your Ford Fusion. It seems like you’ve pinpointed to the problem to that pressure sensor that is keeping your compressor from turning on. Since you’ve tried so many sensors, it seems like a bad sensor might not be your problem. One thing that might be worth checking is if there are any software updates for your vehicle. Its possible new software could correct the sensor to read the correct pressure at the given output. The other thing we would recommend checking the wiring between the sensor and the HVAC module to see if there is anything that could be disturbing the signal which could cause the erratic or inaccurate readings.

      Thanks again for your question!
      -BD Auto Pro

      • Joseph on August 1, 2019 at 1:46 pm

        Ok, I will give that a try, I figured i would go ahead and change out the wiring connector going to the pressure switch and then go from there. I didn’t realize it might be wired through the HVAC Module though so I may take that out and try as well. I know that the first mechanics who worked on the car had the hvac module out and were cutting wires and things trying to bypass an evap temp sensor or something but the evap temp sensor readings are reading good on my scan tool. They may have cut some other wires that shouldn’t have been cut so I will pull that out and try.

        Thank you very much for the info.

  20. Shawn on August 20, 2019 at 10:28 am

    Hello, I believe the compressor in my 2007 Mini Cooper may be failing but not 100% sure. Car is blowing cool not cold air.

    Put manifold gauges on and here are the stats:
    Ambient Temp = 89 degrees (60% High humidity here South Florida)

    After 20 minutes idling without a fan in front of condenser (did these readings first):

    Low = 45 psi
    High = 210 psi

    After 20 minutes idling (I put box fan in front of the condenser to simulate driving airflow):

    Low Side = 47 psi
    High Side = 150 psi

    *Compressor runs but doesn’t ever cycle/turn off unless I push the on/off button
    *I can hear refrigerant hissing in cabin – Does this mean Expansion valve is functioning?
    * Pulled driver side plastic console plate off to access expansion valve. Evaporator lines connecting to valve – one line is cool, other room temp inside cabin. Normal? Should both be cool?
    * Low side line not cold at all

    Have an idea what may be wrong here?

    Safe to assume Low side is a normal, High side is low?


    • BlueDevil Pro on August 20, 2019 at 3:19 pm


      Thank you for asking about your Mini Cooper. Based on the high side and low side PSI readings, it could be that the system is overcharged or there may be an issue with the condenser being blocked. If the refrigerant is topped off to the proper level, it more than likely would be a blocked condenser. The best solution is to replace the condenser in a case like this. Flushing the condenser can save money, but it also increases the risk of a compressor failure or an orifice tube or expansion valve blockage if the flush fails to remove all of the gunk from the condenser.

      Thank you!


  21. tim harmon on June 8, 2020 at 3:46 pm

    2012 F250 6.7, noticed on super hots days over 100 and up the cooling would only work properly when driving at freeway speed around town it will not cool to comfortable temp. So In the past on other trucks I would add refrigerant with a sealing agent added. I followed directions to the letter and ran on max, compressor on, engine to normal temp, I checked the pressure was on the low side at 30 lb. The temp outside was 85, so instructions indicated I need 45 to 55 lb. When I tried to add refrigerant it went all the way up to red and 450 lb. Then I let off and it showed 30 lbs. Stumped as to why it won’t take fluid and up the pressure.

    • BD Auto Pro on June 10, 2020 at 7:12 pm


      Thanks for your question about your 2012 F250. If the gauge is showing pressure when connected then the valve on the air conditioning system in your truck is working and allowing pressure into the feedline of the refrigerant can. It’s remotely possible the valve is bad in your AC system so when you try to add refrigerant it closes off but that’s very unlikely. Our best guess is that the coupler on the refrigerant can you bought isn’t working properly so it isn’t allowing the new refrigerant into your system.

      Thanks again for your question!
      -BD Auto Pro

  22. Ketan on July 25, 2020 at 3:40 pm

    Hello I have a 2011 Hyundai Elantra GLS 1.8 engine. Recently I fill the refrigerant 2 weeks ago and that time cooling was great. But now it’s cooler than before I check with pressure gauge it’s saws when car is run with full ac on is 40 psi and when car is off it’s saws 85 psi on low side.
    Please suggest what is the problem?
    Thanks in advance.
    Please suggest me what’s is perfect pressure keep on low side when ac charge.

    • BlueDevil Pro on July 28, 2020 at 8:29 am


      Thank you for asking about your Hyundai Elantra. Normal pressure readings should be about 30 psi on the low side and between 200-250 psi on the high side. To confirm, are you saying the A/C started blowing cooler after 2 weeks? Please contact our technical support line at 888-863-0426 so that we can get a little better understanding of the vehicle’s condition and be able to make any appropriate recommendations.

      Thank you!


  23. sam on August 3, 2020 at 8:07 am

    have 1940 chevy coupe it has new 350 crat eng. high side of comp running around 300 psi and suction running about 40psi . But comp is cycling on and off about every 50 to 60 sec.

    • BlueDevil Pro on August 4, 2020 at 9:55 am


      Thank you for asking about your Chevy. Is the A/C pumping out cold air? What was the ambient temperature when you took the psi readings? If the compressor is short-cycling, it’s possible the system is overcharged, but this would usually result in the compressor cycling very rapidly. Keep in mind, with the vehicle idling, it is normal for the compressor to cycle on and off every 60 seconds or so.

      Thank you!


  24. David on August 31, 2020 at 11:37 pm

    Nissan pathfinder. low side was 100, high side was 130, then I evacuated freon from low side until low side was 35psi. Now high side is only 70psi. if rev motor, low side drops a bit, but high side stays the same 70psI. clutch is engaging when ac button is pressed on, if the fan is also on,disengages if either is turned off. If ac button and fan is on, clutch is engaged all the time ac is on and never cycles off, ever. cabin air slightly below ambient.

    • BlueDevil Pro on September 2, 2020 at 8:32 am


      Thank you for asking about your Nissan Pathfinder. Was the system overcharged with refrigerant? Based on your description, it sounds like even before you evacuated some of the refrigerant, both the low side and high side psi are out of range. It sounds as though the low-pressure switch may be faulty. This is responsible for measuring the pressure and telling the clutch to engage or disengage. We recommend replacing the low-pressure switch in this instance.

      Thank you!


  25. Rc on June 16, 2021 at 8:13 pm

    What’s a good level for my 2013 vw cc on low side in 95 degree weather. Right now it’s at 35 ac is cold but I think it could be colder. Can I put 45 psi or 50 and be safe ? Thx

    • BlueDevil Pro on June 17, 2021 at 8:36 am


      Thank you for asking about your Volkswagen. On a 95 degree day, the low side should be reading at or around 35 PSI, so it sounds like the A/C is in normal working condition. Try checking the high-side PSI to see if it is abnormal. The high-side PSI reading on a 95 degree day should be about 240 PSI.

      Thank you!


      • JR on July 18, 2021 at 11:33 pm

        Problem: 2001 BMW 330xi. Low side 70 psi, high side 150psi, thought bad compressor. Flushed system, new compressor,drier,xvalve, evacuated to 200 microns, charged, same problem. Installed another compressor, documentation with compressor said if system was flushed, compressor had enough oil. if partial repair, new compressor was to be drained and contents removed to mimic to old one. Originally thought new compressor was fine, but when I removed it it only had 35cc of oil, not the 50%of 150to165bb? So new compressor #2 was drained and it had less than 5cc?? So I added 140cc of oil to new compressor #2, and installed. Now same problem 60psi low side 130psi high side? What do you think??

        • BlueDevil Pro on July 21, 2021 at 8:14 am


          Thank you for asking about your BMW. Based on your description, it sounds like your PSI for the high side is too low and the PSI for the low side is too high. If the system has the correct amount of charge, we’d suspect either air in the system or a faulty expansion valve. The orifice in the valve could be stuck and not adjusting to evaporator temperature.

          Thank you!


  26. Jesse on August 9, 2021 at 10:05 pm

    08 Highlander slow to get system blowing cold, never blows ice cold. At 86F ambient, low side pressure 45psi, high side 185psi. High side seems a little low but low side seems normal. I’d consider charging but am thinking an issue elsewhere?

    • BlueDevil Pro on August 10, 2021 at 9:00 am


      Thank you for asking about your Toyota Highlander. Based on your description, it sounds as though the high side PSI is a little too low and the low side PSI may be a little too high. Unfortunately, this would usually indicate the expansion valve is failing or there is a blockage in the system. We recommend bringing the vehicle into an A/C specialist for possible repair.

      Thank you!


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