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that looks like the relay that controls fan speed, nothing to do with the compressor starting or stopping, the coils control fan speed thru resistance of the coil. usually these are burnt out and fans do not have the different speeds. but it does not operate the a/c.(unless someone has been rewiring the car((Bubba))).
Last edited by lvmyvt76; Sep 20, 2016 at 07:03 PM.
DUB...let me first say thanks for your patience and knowledge! I've got new relay in. However blue wire still has power to it even before it's plugged into thermal switch. That's with blower switch to OFF and ignition OFF. I have a 0 ohms reading on the thermal switch. I do remember in the past repairing the fuseable Linc that supplies blower motor. Also 30 amp inline fuse ok. My next step at this point is it check all contacts in the ac controller wheel in the console as 7T1 stated prior.
that looks like the relay that controls fan speed, nothing to do with the compressor starting or stopping, the coils control fan speed thru resistance of the coil. usually these are burnt out and fans do not have the different speeds. but it does not operate the a/c.(unless someone has been rewiring the car((Bubba))).
Correct. I posted the wrong pic. Below is thermal switch we speak of. According to assembly Manuel it's supposed to open Below freezing temp.
Last edited by Vettesic; Sep 20, 2016 at 09:11 PM.
And if your original is CLOSED....thus an ohmmeter across both terminals would show an ohm reading.....then hopefully your new one is OPEN...and your have corrected the problem
HECK..I meant to look at the wiring diagram for your car today but I had so much going on...I literally forgot.
Unless I am mistaken (and that happens with higher frequency every year ), the 'safety' devices in the A/C system are all designed to turn the A/C system OFF. I don't know of any that, when failed, would turn the system ON. So, I don't believe any of those items could be the cause of your problem.
The only way to have the system turned ON is by having 12vdc delivered to the power wire to the compressor...either via the existing factory wiring/switches of the A/C system or via some modification of wiring/switches performed by a PO or electrictian working on behalf of a PO or by some strange accidental quirk of "old car" wiring.
A "stuck" A/C activation switch on the control head could cause your problem. You might also have some other power wire that somehow is communicating with the compressor power wire; but that would be a rear rarity.
Your primary course of diagosis should be to trace backward along the power wire going to the compressor to find WHERE the 12vdc is entering that circuit.
Last edited by 7T1vette; Sep 21, 2016 at 07:48 PM.
Unless I am mistaken (and that happens with higher frequency every year ), the 'safety' devices in the A/C system are all designed to turn the A/C system OFF. I don't know of any that, when failed, would turn the system ON. So, I don't believe any of those items could be the cause of your problem.
The only way to have the system turned ON is by having 12vdc delivered to the power wire to the compressor...either via the existing factory wiring/switches of the A/C system or via some modification of wiring/switches performed by a PO or electrictian working on behalf of a PO or by some strange accidental quirk of "old car" wiring.
A "stuck" A/C activation switch on the control head could cause your problem. You might also have some other power wire that somehow is communicating with the compressor power wire; but that would be a rear rarity.
Your primary course of diagosis should be to trace backward along the power wire going to the compressor to find WHERE the 12vdc is entering that circuit.
7t1, as mentioned to DUB. I will go th the controller in the console next. I haven't had time to get into that yet this week. Tracing the light blue wire that supplies the green Ac wire is extremely difficult wrapped deep in the harness. For now I'll have to work with volt meter. Thanks.
Ok....here is where I am at now. I have bypassed both blocking relay and dieseling relay. The Ac compressor now actually works as it should. When controller wheel rotated to ac she kicks in. However if I just want heat and rotate controller to heat, ac still kicks in. I would think the heat setting on controller should disengage the compressor??
I'm happy to report that I have removed the compressor contact on the thumb wheel controller. Just as 7T1 states, adjusted the little half loop contact and coated both contacts with a product called Deoxit contact cleaner. Compressor switches on and off as should along with fan including high speed fan working. Fan was a seperate project. I got the cleaner from the copy machine tech at work. Next I will test system for leaks. But that's for another day. Thanks to all for the help!
Last edited by Vettesic; Sep 28, 2016 at 09:56 AM.
I know this is an old post, but I am having the exact same problem on my 75. I am new to the Corvette world so my knowledge is slowing growing. My question is how do you get to the rear contact that ended up being the problem and how do I know what contact it is?
), the 'safety' devices in the A/C system are all designed to turn the A/C system OFF. I don't know of any that, when failed, would turn the system ON. So, I don't believe any of those items could be the cause of your problem.
