Skip the auto shop - Our mechanics make house calls

Q: A/C blowing hot air

asked by on

My a/c just started to blow hot air, I was driving and it went from running cold to warm. I have checked the relay, but the clutch is not engaging and obviously the compressor is not running. My question is if the system has run completely out of refrigerant and tripped the low pressure safety switch or the switch is faulty, how can I get the compressor to kick on so I can get a reading on the refrigerant pressure and possibly fill it if it is empty?

My car has 110000 miles.

Whether or not the refrigerant is low, it can be tested using a/c gauges. The a/c compressor doesn’t need to be running to check system pressure, only to check operating system pressures. You can hook gauges up anytime and see what the resting pressure is, which is what the low pressure sensor is monitoring anyway. It is against the law to put refrigerant into a vehicle with a known leak except for testing only. If you have a leak it could be any number of components, such as the condenser in the front of the radiator or a high pressure line. If you want to check the system pressure you can usually get an aftermarket pressure gauge at a local parts store, though I strongly recommend having a certified mechanic diagnose the a/c issue, such as one from YourMechanic.

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

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 releasing my clutch in first gear, it stutters and vibrates the car.

It's probably clutch related, for example due to worn out friction material and/or a pressure plate defect BUT it's also possible that the motor mounts could be implicated and the engine as well if the engine is bogging down (due...

Q: I have 2007 LS 460 when driving the highway it will pulsate when brake is applied

The pulsating from the brakes are usually caused by the front rotors which are warped and will vibrate the steering while braking. You should have the brakes inspected and brake rotor run out checked using a dial indicator. You will...

Q: I have rebuild transmission and is not driving out of D and D3.

Hi there. Check the shifter cable alignment to the transmission and make sure that the main valve is aligned up properly. The main valve could be off aligned causing the vehicle to not drive in the D and D3 selections....

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...
P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...
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.