Skip the auto shop - Our mechanics make house calls

Q: ac will not come on, clutch will engage

asked by on

last trip out ac was working perfect until I shut it off for a minute. When I turned it back on-nothing. When I stopped to look it over I saw the fan was locked up. So I replaced the fans as a unit, but the ac will still not come. I switched the relay with the wiper relay, still nothing, checked for blown fuses, found none.Then on line a read that it might be the transducer. That when it goes bad the clutch will not engage. I can buy one of those cheaper on line than at any shop. I also tried resetting the system by disconnecting the battery, but again-nothing. Any ideas ?

My car has 175000 miles.
My car has an automatic transmission.

The powertrain control module (PCM) receives input from sensors to determine compressor control. The first thing you want to do is make sure power is getting to the compressor. You can do this using a test light or digital multimeter. If there is no power getting to the clutch, suspect a faulty relay, A/C pressure switch (transducer), wiring, low system pressure (insufficient refrigerant charge), or a blown fuse. The PCM could also be to blame since it directly controls the compressor clutch relay, but its not likely. You can also check the ground side of the compressor circuit using a test light or multimeter.

If the compressor has both power and ground but it does not engage, the clutch, coil, or compressor have failed. Try turning the compressor clutch by hand - if it turns, the compressor is not seized and either the clutch or coil are to blame. Trouble shooting an A/C system can be difficult, so I suggest you give the professionals at YourMechanic a call.

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: Car overheats, usually in the stop and go traffic

The problem may be due to the hydraulic cooling fan not working intermittently. There is a technical bulletin number 1-21-11 that says to replace the cooling fan hydraulic motor, which should correct the overheating problems. Your fan may work but...

Q: Well my car started right up last night I drove it to various place then I went home & when I woke up it would'nt start

I would start with testing your battery and alternator with a multi meter. Good batteries hold a charge of 12.6 volts or higher. If the battery is low, try to jump start it. If this starts your vehicle, test your...

Q: How do I safely clean the rear view mirror?

When cleaning the rear view mirror, it’s important to not spray any cleaning solution directly on the mirror, as this can cause damage. Instead, spray glass or mirror cleaning solution onto a towel, and then carefully wipe down the rear...

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 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.