Skip the auto shop - Our mechanics make house calls

Q: A/C intermintent blows hot air.

asked by on

Starts out blowing cold and some time later starts blowing hot air. Acts like the blend doors are getting changed for some reason. Diags show no fault codes.

My car has 150000 miles.
My car has an automatic transmission.

A: Sometimes the A/C cycling switch will cycle...

Sometimes the A/C cycling switch will cycle the A/C off like it should when the temperature reaches cycling pressures of about 24 psi. Once it cycles off and the pressures rise to the set pressure to cycle back on, it does not cycle back on and the A/C starts getting warm. The intermittent low pressure cycling switch is the most common cause of this problem and should be verified to be the problem by a qualified mechanic. Replace the cycling switch and retest the system to be cycling on and off correctly. If you need help getting this checked, have a certified professional from YourMechanic come to your location to inspect the AC system and move forward with the appropriate repair.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: When I switch from heat to AC, the heat still blows?

Hi, thanks for writing in. If your heat is still blowing when the air conditioning is turned on and the compressor is working, then it is likely that the blend door actuator has failed. The blend door actuator is responsible...

Q: Ground wire off oil pressure sensor melts

The wire to the oil pressure sensor is only a ground connection from the oil pressure sensor to the instrument cluster. If you are seeing this wire smoke like it is getting melted, then you have either a short...

Q: I replaced my oil sending unit and it screwed I further than the old one kinda thinking i screwed up

The oil sending unit has threads that are tapered and the new sensor may have less of a taper than the old one, causing it to screw in farther. Be sure that you don't over tighten the sensor. You should...

Related articles

P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the P0052 code means This code is seen when the Engine Control Module (ECM) tries to control the...
How Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.