AC Compressor Squealing
 

I have recently redone the AC on my Can Am. Everything is working and cooling fine except for one problem. Sometimes when I am sitting at a stop sign or red light at low rpm's the compressor starts squealing. I can turn the ac off when the compressor squeals and wait until I am running 20 mph or so to turn the ac on and the compressor will not squeal anymore while I am at speed. I can drive 20 miles or so at highway speed and the compressor does not squeal so I do not think it is a problem associated with the compressor getting hot. Any suggestions? Thanks.

A/C Problem
 

Sounds like your A/C system is building up pressure at idle, which can mean your fan isn't pulling air through your condenser. Do you have a bad fan clutch? It could also be your system is overcharged. You belt is loose or wore out.


67 Tempest OHC 3 on the tree

What did you have redone? Like GOLDOHC said check the belt.

I have a new compressor, accumulator and evaporator. The ac hose assembly has been rebuilt. The belt is new and seems to be tight enough so I do not think it is the problem. I think it may be the fan clutch. The fan does not move much at all when I spin it with my hand. Isn't that an indication the clutch could be bad? I have also noticed the car is running a little hotter than it used to run. Thanks for the suggestions.

I agree with the pressure spike at low speeds, check fan/clutch air flow through condenser

a fan clutch has an internal thermostat that locks up at a certain temperature, warm your car up, turn on the a/c, open the hood, there should be a lot of hot air coming through the fan.

I am a novice at all this. Are you saying I should feel the hot air at the front of the car when I open the hood after I have warmed the car up and the ac is on?

I went out and let the car warm up. Turned on ac and opened hood. I do feel warm air moving around the engine compartment. I then drove the car. Ac worked fine but as soon as engine rpm got between 500 to 1000 compressor started squealing. I got out and looked real quick and it appears the belt is slipping on the compressor pulley. The belt is new and seems to be the right tightness. I turned off the ac and then got back up to speed around 2000 rpm, turned on the ac and it worked fine for 5 to 10 miles until rpm dropped to 500-1000 range again and compressor started squealing again. Engine temp gets up to 200 or so and does not begin to drop until I turn the ac off.

Check the shroud to radiator fit. I've been using foam weather strip from hard ware store and get it sandwiched between radiator and shroud for a zero gap.
A new HD fan clutch may be in order.
Is the A/C Idle up solenoid on the carb operational?**
Is it a 7 blade fan?
Is it the Valve In Receiver (VIR) style system.

The seal appears to be good but I may try some insulation. The solenoid is operational but I am not sure if it is adjusted properly. When I turn ac on, the solenoid pops out but it does not touch anything to change idle. I am not sure what a VIR system is. Does have 7 blade fan.

I think I may just need to adjust the fast idle solenoid and my squealing problem may be solved.

Sounds like too much head pressure.....

I have done some more research and this is what I have found. I adjusted the fast idle solenoid so the idle speed is not the problem. I have noticed the compressor is not cycling. It was previously but did not cycle any tonight. I hooked gauges to the low side and the pressure with the ac on is around 40 and it is cooling fine. The pressure starts rising and the compressor starts squealing when the pressure rises to around 50. Isn't the compressor supposed to cycle to keep the pressure at an acceptable level? What could be the cause of the compressor not cycling now? Could the system be overcharged? The 134 retro high side fitting is not any good and I can not check the high pressure until I get a new fitting.

Just went back out and started ac with car at 2000-2500 rpm. AC cools fine and low side pressure is constant at 38-39 with no cycling. Compressor starts squealing as soon as rpm is decreased.

Some of the a/c cars had a two wire hookup by the evaporator, that would cycle the compressor when the evaporator would drop below a set temperature. If I recall it was called a thermistor. Your correct, your low side temperature sounds high, but that doesn't mean it is overcharged.

Your not bringing enough air through the condenser. At 2000 rpm (in park)hi speed fan and MAX or recirculate bring your low side to between 30-35 on the gauge. This will give you very close to the right amount of freon. With all that if your situation does not better at an idle. Buy a heavy duty fan clutch such as a Haydon. You need to get as much air through your condenser as possible!!!!!! You are running 134A in a system that was designed for R12, the condensers on cars designed for 134A have more fins per inch. No real need to change the condenser though. I run 134A in my 71 T/A with no fancy tricks, ice cold on a 95* south Florida day, five years now.

The low side readings do not tell the story. You need to have someone check the high side reading. If you do it yourself be careful it will likely be reading 200+ PSI even at idle.

If the fan or clutch is not doing their job pulling enough air through the condenser, then the high side reading will rise dramatically (300+ PSI!!). This can definitely put excessive strain on the compressor making the belt slip. Once you get moving (20mph) the air flow through the condenser improves and the high side pressure stays in check.

If you cannot get the high side reading you can spray water on the front of the condenser and see if the squealing stops.

Be careful you are dealing with extremely high pressures on 1/2 of that system.

I put a new fan clutch on the car and everything seems to be good now. I drove the car around some and had numerous stops where the rpm dropped to 1000 or so and the compressor never squealed. Engine temperatures also seem to be more consistent. Thanks everyone for your input and help!

UPDATE: The ac has squealed a couple times after I changed the fan clutch. It seems the compressor never squeals when I am on MAX but it has squealed twice when I have the ac set to NORM with the fan on high at stop or very slow speed. Any thoughts on why it will squeal at NORM but not on MAX? Thanks.

The only difference in NORM and MAX is that MAX recirculates inside air while NORM pulls in outside air. I always run on MAX here in Florida. I think you still have high pressure in the A/C System. So get it checked. Be sure you get all gaps sealed between the condenser and the radiator and shroud so that all air has to be pulled through the condenser. I know its overkill but it should have been that way from the factory. Be sure the belt is in good condition and tight enough. Be sure to use a TOP quality belt, the cheap ones stretch and may not fit the pulleys correctly. High pressure puts undue strain on the compressor and thats why it may squeal. Is the system overcharged?

Belt tension or alignment is my best guess..

If you've glazed the belt, it's toast and needs to be replaced. Even with a new belt, if it wasn't installed with the correct tension or the pulleys are not aligned, it will slip and squeal as you describe. Once glazed, it will ride too low in the pulley and continue to squeal until replaced. The belt needs to ride on its sides within the pulley. You also might have to sand the pulley with 200 grit or super fine steel wool to remove the old glaze.