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.

A: The powertrain control module (PCM) receive...

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: Transmission fluid sensor has a higher reading than what is the actual amount

Hi there, This transmission (4l60E) nominally holds 10 quarts. It is "flushed most effectively by a machine that pushes fresh fluid in at the same time old fluid is pumped out (with the engine running), and with a 12 qt...

Q: Replacement oxygen sensor going dead

Hello. I need more information in order to pinpoint this concern as your vehicles V6 engine comes equipped with 4 oxygen sensors. I need to know whether or not the concern is turning on the Check Engine light, making the...

Q: Coolant leaks as soon as I add it to the radiator tube while Car is off and cold.

Hi there. Look at the engine and try to locate where the fluid is coming out of. Most likely the coolant is leaking out of a heater hose next to the engine by the firewall. If the hoses are good...

Related articles

How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...
What are the Car Pool Rules in Hawaii?
Hawaii is widely regarded as a land of vacation and relaxation, and as such, its scenic roads and routes are far better known than the state’s freeways. But, as with all...
P2428 OBD-II Trouble Code: Exhaust Gas Temperature Too High Bank 1
P2428 code definition A P2428 trouble code signifies that the PCM has detected a problem in the exhaust gas temperature sensor circuit in bank 1, which subsequently contains the number one...