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・Save up to 30%

Get a quote

What others are asking

Q: How do I adjust the remote start driver seat?

When the remote start driver seat is turned on, then the driver seat’s seat warmers will automatically turn on when the vehicle is started via remote start. To turn this feature on or off, follow these steps: 1. Press the...

Q: No brake lights. Bulbs are good and 3rd brake light works. Problem?

Hello there, thanks for writing in. It seems that faulty brake lights are a common problem with 2000 Pontiac Montanas. If the 3rd brake light works than the brake switch is working properly. The most common causes would be a...

Q: Weather warm engine starts no problem, morning won't start up no fuel smell, cranks only

Hello. Thanks for writing in about your 1995 Lincoln Continental. The symptoms you describe are a bit unusual, as it is most common for a vehicle to do the opposite, start easily when cold, and then have difficulty starting later...

Related articles

What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
How Long Does a Distributor O Ring Last?
The distributor is part of the ignition system in your vehicle and its purpose is to route high voltage from the ignition coil to the spark plug. The spark plug then...
How Long Does a Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...