QuestionThe a/c clutch is not energising.There are several relays under the hood. I need to be able to locate and identify them all so they can be marked for later use. Can you help me with true logic statements for my clutch to operate? Like where to find the temp sensor, control relay and a method to test this circuit?
AnswerMckinley,
As for the specific locations of the components on a 1989 sunbird, I can't help you too much there. I have absolutely no literature on that vehicle. I will look online and if I round anything up, I will do a follow up with you on this.
The basic circuit goes as follows..., and from the sounds of the way you wrote, you know a good bit about electrical circuits, so I won't insult your intelligence and tell you how to check for voltage at certain points. If I have mis-read though, please let me know and I will walk you through the system checks step by step.
Here goes...
The control head receives input signals from where you set the knobs. From there voltage travels to your A/C clutch relay. Usually in the underdash box... as for which one... I would check the cover of the box, your owner's manual, or a chilton/haynes for the layout of the relays. Your A/C clutch relay energizes and sends voltage to your Thermostat. The thermostat is under the dash mounted on the evaporator in the passenger side of the cab. The thermostat stays closed until your passenger compartment registers in the neighborhood of 70 degrees on a hot day. Power then travels out of your thermostat to a low pressure switch. The low pressure switch is usually located on your accumulator. (A silver canister about the girth of a soda can with 2 hard refrigerant lines coming from the top) With your low side pressure above 17-22 psig (typically) the switch closes and sends power to your high pressure switch. (The high pressure switch is usually located on your receiver, a black canister again about the girth of a soda can, with 2 refrigerant lines attaching to it with fittings) This switch remains closed until your high side pressure reaches 380-420 psig (typically) and power travels to your compressor clutch coil, energizes your clutch coil and compressor runs. If your low and high switches are not where I said, trace your lines leading from the compressor until you find them, they may be connected straight into your lines.
At each point inthe circuit you should read 12VDC, and each point you can safely jump to check .
I hope this is what you were looking for from me, if not let me know and I will go in deeper. As I said, I will continue to look for a layout of your relay box, but you can probably just do a continuity check from your low pressure switch to each relays working contact and it will tell you. But the first place I would check is your low pressure switch. It is most accesible usually and will tell you which way to work the troubleshooting process.
Thank you for the question, if you need more let me know.
