Question. How to get AC clutch to activate on 1992 911

[x98boardwell]

Okay, here is what is happening. The air conditioning clutch on this car (that has sat for 5 years and we just brought back to life with 33,000 miles) will not engage.

- We have checked the fuse in the rear of the vehicle (7.5 amps)
- We have checked all wires that connect to compressor (black with spade connector inside clear plastic sleeve by oil filter)
- When we turn the A/C switch on in the car the blue light comes on and almost seems like their is more drag on the engine for a quick second but clutch still doesn't move.
- Not sure what to do.
- We have also changed fan speeds and recirculation switch as well just to be sure while the car was running.

I just had a thought, if the system is low or has no R12-R134 (in this case R12) will the clutch not engage as a safety feature? Any thoughts on how to fix this issue or get the clutch to engage and work?

One last issue, Steering rack & pinion, there is one of the black boots (where the steering arm comes out of the rack and pinion) that has swelled up from leaking fluid and has disengaged from the rack. How do you replace that rubber accordian style boot? This is the one that passes just above the lower control arm on the way out to the other end of arm where there is a ball joint looking connection.

Any help is appreciated.

Thanks,
Bryan

[timmy2]

There may be a pressure switch that won't allow the clutch to engage. Check the wiring schematics for the car's AC system. (May even be internal to the compressor)
Have you checked the resistance value (ohms) on the clutch solenoid at the compressor? If it is open (infinite) then it will never engage and needs to be repaired.

[x98boardwell]

I haven't checked that and I will... Thanks.

[T77911S]

i dont know the 92 AC at all, but based on experience working on AC, i would get a test light (or multimeter) and check for power at the comnpressor clutch. since you say the blue light is on for the AC, i would assume (dont really like to, but as a place to start i will) that it is sending out 12v to engage the compressor. so if no power at the clutch i would work backwords. some comp's have a temp sensor on the back that go bad or even a pressure switch. check for those. then i would continue to backwords checking each connector.
if you know that it has a pressure switch, you might jump to that and make sure power is getting thru it. if no power to the pressure switch (or any connectors) go back and check the controls to see if it is putting out 12v.
some controls operate on evap temp. even though the blue light is on, if the evap temp drops to a certain temp, the blue light stays on but the compressor is cut off until the temp rises. that switch inside the controls could be bad.

low pressure switches will stay closed to pressure down to around 20 psi or so, so it does not take much of a charge to close the LP switch.

[stormcrow]

Bryan,

There may be a low pressure switch that cuts off the compressor when it is low on refrigerant. Here is the way to check it out.

Have someone sit in the car to start the car. Take a volt meter and connect one end to the ground or chassie (black wire) and connect the other end to the terminal that plugs onto the compressor - make sure it stays connected to the compressor.

Set the meter to volts DC and have the person sitting in the driver seat start the car. What should happen if the pressure switch is taking control because of low refrigerant you will get a 12V reading and then no reading - you can also watch the clutch on the compressor it will probably enagage and then disengage.

Now, if with the engine running you get 12v reading continuously and the clutch on the compressor doesn't engage, then the clutch coil is bad.

Hope this helps.

SteveKJR