On the VIN A (231) there is no relay but it does send the signal to the ECM so it can control the idle.
On the VIN 9 and Y (307) the relay is controlled by the computer not the switch. The computer gets the signal from the switch and other positive voltage switches and controls. The relay can cut off or enable the ground to the relay coil turning off the compressor clutch.
I believe the computer does this to turn off the compressor under non wide open throttle loads, like climbing a hill or other heavy loads at part throttle.
The switch can carry sufficient current to control the compressor clutch, the computer cannot.
In a nutshell, the above is sound information.
Just to clarify this a bit. The ECM gets involved to help control the idle control for VIN Y ILC solenoid as well (VIN 9 has a carb idle solenoid that IMMEDIATELY gets energized when you turn on any mode needing the compressor).
The ECM plus the A/C control solenoid on VIN Y and 9 comes into play during hard acceleration events, high coolant temperatures, and disengages the clutch for 3 seconds during startup on a warm engine. I think I read somewhere too that when decelerating to turn on a mode that requires the compressor, it delays the engagement for 3 seconds based on TPS position. Something like that. It's in the CSM somewhere. I'm not an electrician, but I pretty much understand what it's trying to do, so some of this can get a bit confusing in my ham-handed descriptions. Not everything in the electrical manual and CSM connects the dots nicely when it comes to ECM-controlled stuff.
Now here's where it gets weird. In looking over this in the ECM Chart C-10C in the CSM, I noticed that the A/C compressor control solenoid (little black cube solenoid next to the accumulator) for VIN Y is drawn correctly, but the VIN 9 isn't quite reality the way I see it. It's drawn correctly in the diagram above, however. The VIN 9 solenoid shows normally closed when de-energized in the C-10C diagram. If you have a CSM with this, the solenoid is normally OPEN. It uses the same solenoid , although the B and D terminals are swapped for the contacts, it shouldn't make any difference. It's still the SAME PART NUMBERED N.O. solenoid. The way I understand it, you may can do this with a 5 pin, but a 4 pin is pretty much an ON/OFF switch. Or am I missing something here?
Hi coolant temperature is mainly what the ECM cares about. The VIN A ECM monitors coolant temp and when it sees high coolant temps (~258 F), it "ungrounds" the clutch and that's it until coolant temps come down.
The Olds VIN 9 through 1985 has the WOT cutoff switch above the gas pedal. It's an instant clutch release when you stomp the gas pedal. What this does is it ensures the clutch disengages immediately when stomping the gas. I think some Regals had this gas pedal switch too, but don't quote me on that.
When the A/C selector is moved to a position that requires the compressor to be on and ECM determines conditions warrant, for the VIN Y and 9, the ECM grounds to CLOSE the B/D contacts on the relay which then grounds the clutch solenoid. Then it allows the pressure cycling switch to control the clutch for the most part. If you want to check real quick if the ECM "ungrounds" your clutch at WOT, start the car, turn on your A/C, ground your green clip diagnostic test terminal under the hood, then take a tweaker screwdriver and push your TPS plunger all the way in and see if it doesn't cut off the clutch after a second or two. Note, you may have to clear a code afterwards when doing this.
This is why the 80s Olds V8s didn't need a high pressure cutout switch, because it would disengage the clutch anyway under high load/high rpm conditions. I can't tell you what the deal is with other cars that use the switch.
If you need a new solenoid, you can find it under the latest supersession GM/ACDelco p/n 10039961 which can be used for 82-88 VIN Y or 9. Or aftermarket equivalent, like Standard RY-85, or Four Seasons 35915.
#1 is the WOT cutout switch/bracket above the gas pedal.
Here's that "chart" description that seems a bit messed up. I can't see how it can work the way they depict it. But the description seems to be ok but I believe on the third line where it says "VIN 9", I believe that should be VIN Y". If terminals A and C on the relay aren't energized, the relay stays OPEN. They swap B and D terminals, which I think would be 30 and 87 normally (which I thought was verboten practice), but I can't see how it can make it a normally closed circuit with a 4 pin relay when the parts callout says it's a 4 pin N.O. relay for both VIN Y and 9. Interestingly, the ECM boxes themselves are the same part number for VIN Y and 9, the only difference is the PROM chip.
The only way I can see it working is if the VIN Y terminial 19 on the ECM grounds immediately when it gets an A/C "on" signal where the VIN 9 does not. Then, if conditions warrant, like high coolant temps, the VIN 9 Terminal 19 grounds and opens the circuit. But then, if both VIN Y and VIN 9 use the same relay...yikes. Making my head spin. Something isn't right with this.
You can see here, the same part number for VIN Y and 9. Even in the B, C Diesel and D body.
