I found the biggest problem with my AC today, I turned it on, hoping it might get cold, and then looked under the hood. I saw that the clutch for the compressor wouldnt engage, it was stuck in the disengaged position. I have a good logicon, because it worked fine in another car, so its not sending a bad signal. Is there any mechanical reason why it could be disengaged? I turned the car off, and pushed the clutch against the wheel, and let go and it sprung back out. Also, i think it might have been broken before because there is an odd wire that goes to it with new wire connectors.

Please help me out here, I'll answer any question i can.
thanks,
Ian

 

The clutch is magnetic and its natural position is to be sprung out. When the compressor gets power, the magnet will suck the clutch toward the pulley. The pulley turns the clutch, which then turns the shaft that turns the pump.

There are 2 switches in the system. A high pressure switch and a low pressure switch. If the coolant pressure is too high or low, the switch opens up and interrupts the power to the compressor, disengaging the clutch. Also, on most, if not all cars, there is a relay that will kill power to the compressor when you are at full throttle. This frees up power for the engine to transmit to the rear wheels so you can do stuff like pass cars on the highway. Since your system won't turn on, your low pressure switch is probably preventing it. You may need to service the freon. As far as the wire splicing you described, I don't know what that could be.

 

double post

 

do you know which section of the FSM the AC is in? I looked, but only found heater stuff.

 

it doesnt come on at Idle, or anytime, would that be all the low pressure switch, and can I test the magnet by just taking 12 volts off the positive battery lead, and touching it to the wire that goes to the magnet?

 

your probably low on refrigerant. get your system recharged or bridge the low pressure switch to see if that will turn the compressor on. if it does then you will need a recharge.

 

For some reason there doesn't appear to be an HVAC section in the online S4 FSM. Just download the S5 HVAC chapter instead. Most of the info's the same.

If the compressor won't engage the most likely problem is you're very low on refrigerant. There's a low pressure switch in the piping next to the drier, the aluminium bottle under the plastic shrouds in front of the radiator. If you unplug the pressure switch and put a jumper wire across the plug's terminals, this will simulate sufficient pressure and the compressor should engage. If it does, you're definitely low on refrigerant. (Only do this for a few seconds to confirm either way; run it too long and you'll damage the compressor.) If it still doesn't engage it's probably an electrical problem.

If you're low on refrigerant, you probably have a leak somewhere that needs to be found before you refill the system. Best thing to do is to take it to an automotive A/C specialist.

 

Okay, thanks guys, But how does the jumper run, from the positive lead on the connector to? (getting S5 FSM now too)

 

The s5 fsm on RX7City doesnt have the HVAC section either. And my car is an 87 base.

 

That switch has two sockets. Jumper a wire between the two sockets with the a/c turned to ON and the engine idling. Clack goes the clutch on the compressor, indicating........your LOW ON the refrigerent.

If the clutch does not go klack.....get your meter out and see if there is 12v on one or the other sockets with the a/c to the ON position. Idle the engine (probably not required, but I don't remember right now).

 

okay
Thanks, i'm going to try it rigth now.

 

Alright, i'm low on refirgerant. Thanks to everyone that helped me out. Now, does anyone know of a good car AC shop in fairfax county VA?