After having my AC serviced (new relays and refrigerant recharge), I have the following problem:

When the AC shuts off (via the main switch or when the thermostat cuts off), the idle boost and fan shut off instantly but the compressor clutch disengages about 2 seconds later. During those 2 seconds, the RPMs drop to a near stall. I imagine that this is because during this time, the idle boost is no longer activated. Also, when driving at high speeds, the compressor engages even with the AC is OFF (cold air comes out of the vents). I checked the voltage at the compressor clutch with the AC off, and it reads 0 volts. This leads me to conclude that the problem is mechanical.

Any ideas? Can the clutch engage “partially” if the clutch bearing develops too much play? Is there any way to adjust (increase) the gap between the friction surfaces?

THANKS!
Adam
91 CRX 1.6i16

 

I sounds to me like the clutch is junk. Let me guess- The A?C was not working for awhile, you just got it fixed and now this? This is why they tell you to run the ac a few times during the cold months, so everything keeeps moving.

 

Thanks for your reply.

You’re right about the sequence of events, but the clutch electromagnet is new, and the clutch in itself engages properly when activated (with the 12 volt signal). The problem is that it engages “partially” at high speeds without the 12 volts (AC off), and seems to have a delay when disengaging (with thermostat cutoff).

I’m going to try loosening the tension on the pulley belt. If the pulley bearing has play, and the belt is too tight, the pulley may just be continuously rubbing the clutch plate.

Thanks,
Adam
91 CRX 1.6i16

 

hrmm it sound more electrical to me.. reason for this.. the clutch is not like what ur thinking it can only engage through electricity. Its not mechincal. If i were you i'd run the multimeter leds. Inside your car and watch the voltage as your driving. This will tell you alot.. if it is getting voltage when it should be, take it back to the shop and show them.. its proably a faulty relay or something. If its not and its coming on without voltage.. replace your compressor

 

Thanks for your reply.

Maybe I should consider the possibility that I have more than 1 problem.

As for the engine RPMs dropping when the AC shuts off, I pretty much ruled out the possibility of an electrical problem last night with a few tests. I measured the voltage at the clutch electromagnet under different conditions. It only receives 12 volts when the AC is on. The clutch is clearly getting power only when it should. This is so at least when the engine is running with the car at a standstill. The problem is that when the power cuts off, the clutch does not disengage instantly, and without the idle boost activated, the engine RPMs drop.

As for the compressor engaging while driving at high speeds I figured a continuous rubbing between the pulley and clutch plate (at high engine RPMs), may result in sufficient torque on the compressor shaft to get it spinning. I guess I’ll try loosening the belt and see what happens. If that solves the problem, I will most likely need to change the pulley bearing. If it doesn’t, I´ll check the voltage while driving, like you suggest.

Thanks!
Adam