Skip the auto shop - Our mechanics make house calls

Q: possible electric A/C compressor and fan actuation problems/low refrigerant possibly shutting off compressor?

asked by on

My air never worked 100% ever since I've had my car. (7 months) It took about 20 minutes to get cool, and even then, never got super cold even on full blast. Maybe a recharge? But the big issue is/was the control unit in the dash went berserk one day. The lights on the panel stayed on without the key, the fan speed would work without the key, even trigger engine fans, then broke altogether. Thing is, that was just a blown fuse! Put a new one in, and the control unit works perfectly (or at least seems to), BUT the compressor and condenser fans won't work with the AC turned on, when they did before! All this happened at the same time and the fuse fixed the control unit but not the compressor and fans! I got a screwdriver (no room for my hand) and pushed the comp. clutch. It spins freely. Condenser is spotless. Both fan fuses are good. No comp fuse that I've found. System still pressurized w/ r134. Low refrigerant not letting comp turn on? Faulty wiring to the fans and compressor? Ideas?

My car has 203500 miles.
My car has an automatic transmission.

A: Something blew the fuse and is likely the s...

Something blew the fuse and is likely the source of these problems. If power was supplied to all these systems with the key off, that means there is a wire exposed to power that shouldn’t be. This is known as a short to power. This can happen with a wire or a module. Either way, you will need to figure out what has failed that blew the fuse. Also, you should check all the other fuses. It is common when something like this occurs to blow more than one fuse, whether it is part of the same system or not.

It sounds as though this is a separate issue from the A/C system that doesn’t perform as it should. An under performing system is usually a result of low refrigerant, but there are other possibilities. You will need to recover what is in the system and weigh it. This is the only way to know if the system is full. Pressure in the system will exist until it is almost completely empty, so this isn’t a good indicator of the amount of refrigerant in the system.

If the condenser fan doesn’t work, the high side will spike and the system will not be able to cool. The condenser could be plugged with debris as well resulting in the same thing as a condenser fan failure.

There are three separate parts of this system you will need to look at. The condenser operation, the control panel failure and the amount of refrigerant in the system. It seems there is more than one failure, which means you will need to test each part of the system independently of the other. I would begin by recovering the refrigerant. Of course this isn’t something most people can do, so I highly recommend booking an appointment with one of our technicians to service your A/C system.

Once you know there are no leaks, or you have found and fixed any leaks, you can move onto the condenser fan relay by finding the relay that powers it. Remove it and with a wiring diagram you can supply power and ground with jumper wires to turn on the condenser fan. If the fan runs when you do this, then you know they are good, if not, you should make sure power is reaching the fan. If it is, you need a fan motor. While the relay is removed, make sure it is receiving power from the radiator fan control module.

Next, you should check to see if there is power getting to the A/C compressor relay. This relay is powered by the A/C switch in the heater control panel. Most likely you will find the problem that blew the fuse or fuses in this panel. If you don’t have power to the compressor relay, you will need to remove the A/C switch to track down where the failure has occurred. It maybe a good idea to inspect the back side of the entire heater control panel. Other electrical components could have melted and or damaged wires leading from the A/C switch.

If the compressor relay has power, the next thing to check for is a ground coming from the PCM. It is actually the PCM that decides to turn on the compressor clutch. You can use a jumper wire to ground this circuit to see if the compressor clutch engages. This can be used to test the rest of the system, but be careful not to ground the wrong wire as this may blow fuses and or damage other parts of the system. If grounding the compressor relay turns on the system, you can connect A/C system gauges and see how the pressures are. Be sure to turn the system off when the high side gets up to around 250 psi, otherwise you could rupture a hose or damage the compressor.

If it is found that the PCM isn’t supplying a ground to turn on the compressor clutch, you will should suspect the cycling switch. Cycling switches are common failures. There should be only one in your system and it will have two wires. One will be red/white and the other one will be blue/yellow.

Good luck. I hope this will help you figure this out. If you feel like you need help with these checks, feel free to contact a certified mechanic who will be able to diagnose your A/C system firsthand and fix it accordingly.

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: Clutch pedal going all the way to the floor

This sounds like a hydraulic issue. There is a leak in the clutch hydraulics. The leak could be the master cylinder, slave cylinder, or a line or hose. Follow the lines from the clutch master cylinder down to the transmission...

Q: Windshield wiper assembly question.

Hi there: If you got the replacement parts from an auto parts store, you might want to verify that the replacement parts were for the right model and year of Pontiac Sunfire (as this is a common problem with auto...

Q: Stalling problem

Hi there, thanks for writing in. Your car has an idle air control valve that commonly fails. The purpose of the idle air control valve is to allow enough air to bypass the throttle body to keep the car idling...

Related articles

How Do Power Car Windows Increase Passenger Safety?
Power windows are responsible for approximately 2,000 emergency room visits every year. When a power window closes, it exerts enough force to bruise or break bones, crush fingers, or restrict an airway. Though...
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...
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...