Why is My AC Only Blowing Warm Air?

ac vent, ac only blowing warm airIs your ac only blowing warm air, or only blowing hot air?  The difference could be the difference between a problem with your air conditioning system vs. a problem with your ventilation system.

If you have HOT air blowing from your vents even with the air conditioning on it could be a ventilation system problem.  To check, pop your hood and find the refrigerant lines going into the cabin of your vehicle.  If one or both of them is very cold then your air conditioning is working fine.  If this is the case you probably have a broken air blend door or door actuator.  This door sends ventilation air either over or around your heater core.  The system usually defaults to the “hot” setting if something breaks to make sure you can still defog your windshield for safety.  If this is the case you may simply need to replace the actuator or you may need to replace your HVAC module if the door is broken.

If you have your ac only blowing warm air then it’s possible your air conditioning is having problems.  

Causes of AC only blowing warm air:

  • Electrical problem
  • Worn out compressor
  • Clog in the system
  • Incorrect amount of refrigerant

Electrical problems can be extremely frustrating whether they are with your air conditioning system or not.  If your car is newer than 2000 it’s possible the air conditioning system is run by a computer that can be connected to a diagnostic tool just like your engine’s computer.  This is the easiest way to check for electrical problems in your system.  If you’re not that lucky, check out our article on diagnosing electrical problems.

Your AC compressor is a pump and like all mechanical things it wears out.  The refrigerant in your system has a lubricant entrained in it so if you ever have your refrigerant replaced, make sure you add compressor oil of the correct type as well.  The magnetic clutch on the compressor can fail as well which will also cause your compressor not to compresses, but either way, usually, the best option is to simply install a new compressor.

When your compressor fails it can spit debris into the rest of your system clogging the small passengers in your condenser, evaporator, dryer or expansion valve.  Clogs in your system create abnormal pressures and restrictions which can also cause your ac to blow warm air.  Sometimes this debris can be removed by flushing or blowing out the component but oftentimes they simply have to be replaced.

Either too much or too little refrigerant will cause your system to malfunction.  Too much refrigerant will cause your system to trip off due to excessive pressure.  Too little refrigerant and the pressures won’t get high enough to cause the cooling effect.  The only way to know how much refrigerant is in your system is to evacuate the refrigerant and weigh it.  At that point, it is easy to put the correct amount back in.

If you find out you have the too little refrigerant in your system then you must have a leak.  If you can’t find the leak or replacing the broken component doesn’t make sense for your car, consider using Red Angel AC Refrigerant Stop Leak to seal the leak.  Red Angel AC Refrigerant Stop Leak contains 2.5 oz of refrigerant to top off your system as well as a powerful sealing agent we’re so confident in it we guarantee a permanent repair or we’ll give your money back!

You can pick up Red Angel AC Refrigerant Stop Leak at one of your local auto parts stores like:

  • AutoZone
  • Advance Auto Parts
  • CarQuest Auto Parts
  • NAPA Auto Parts
  • O’Reilly Auto Parts
  • Pep Boys
  • Canadian Tire
  • Walmart

Photo by Olav Tvedt on Unsplash