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A/C, Heating and Cooling / AC Clutch not engaging 85 Hot Air
« Last post by Big Dawg on October 08 2025, 11:42:45 PM »Hey everyone, been a long while since I've posted.
Here goes, I'm having an issue with AC Clutch not engaging.
I posted on the turbo buicks forum as well, but not much response as of today. Sorry in advance if I'm all over the place on this post. I cut and pasted my post from.a.couple weeks with my most recent post.
Okay so I switched my AC compressor (already Converted to R134 by me a few years ago) for new one as my clutch was messed up. I unplugged my ac compressor pigtail on the unit until I had installed a new one and had a shop put the refrigerant back in. Once it was all ready and I fired it up...the compressor wouldn't engage. I checked the fuse on the drivers side and it was fine. I checked the pressure switch and the pigtail and it was getting voltage.....bu t the pigtail to the compressor wasn't. So I checked the relay and it is toast. I jumped the pink to the green wire and clutch engaged.
The relay came in from Rockauto and AC clutch still doesn't turn on.
Here's what the voltage is at the relay plug...with the relay disconnected and car started
Relay plug
Pink with Black stripe 13.85-13.89 v
Dark Green .020 ( goes to compressor plug)
Green with yellow stripe 0 v
Blue 2.45V
Pressure switch (unplugged)
Light Green 3.30-3.33v
Blue 0v (as it is unplugged)
With the pressure switch completed both sides of switch have 3.30-3.50 Volts
Ac compressor wiring ( with ignition on only) and relay plugged in
Green - 0.10v
Black - 0.01
I have no idea what is going on. When i jump the pink and green wire on ac switch relay plug the compressor clutch engages and than eventually starts a small squeal and than after a couple engagements of me disconnecting jumper and connecting 12v the clutch engages but doesn't spin with pulley This is what was happening with my previous ac compressor and clutch as well and I though the clutch was bad. After this happening to the new compressor it's something entirely different.
Update the squeel is gone after I changed the ac compressor harness with diode with a new replacement..i jist jumped the relay pigtail.
So I ordered the relay and that didn't help. I also ordered the correct R134 Pressure Switch and that didn't help.
I even got another ECM and swapped my Prom and TT chip and still no dice.
My old relay and the new relay just click away until I turn off the power at the Digital Climate box......does it when it's set to hi 65 heater option....no clicking on Auto at 65 hi.
I have scoured years of post in regards to this issue and still no luck. I have used my multimeter and followed the tech pages on GNTtype and the other forums. I have checked the power at the harnesses of the heater module (New from Kirbans)...there us 12volt present at the brown 5 pin Harness. There is the light blue wire from pin B8 that splits off into 2. I have jumped the pressure switch and nothing. When I jump the pink/black wire amd the green wire the clutch engages. I have pulled out the Digital Climate Control Unit and checked voltage at the 3 connectors and the different wires as per the instruction on the diagnosis writeups from the factory manual and everything seems to be in working order. I have checked all the Fuses under the dash and all are good...none are burnt out.
My big question is what triggers the B8 pin to energize and send 12v through the green wire to the Compressor Clutch.
Is there any other fuse or relay that I am missing somewhere? The 85 Ac Compresser only has 1 pigtail as ther eis no high pressure switch or factory electric fans. I replaced rhe pigtail wirh the green and black wire with a new one with diode...thinki ng that it was faulty.
The compressor is new and has been filled R134, the system has been tested and has full vaccum...no leKs anywhere.
Please if anyone has had a similar issue throughout there time with there car please send me any info.
Thanks Am
Here goes, I'm having an issue with AC Clutch not engaging.
I posted on the turbo buicks forum as well, but not much response as of today. Sorry in advance if I'm all over the place on this post. I cut and pasted my post from.a.couple weeks with my most recent post.
Okay so I switched my AC compressor (already Converted to R134 by me a few years ago) for new one as my clutch was messed up. I unplugged my ac compressor pigtail on the unit until I had installed a new one and had a shop put the refrigerant back in. Once it was all ready and I fired it up...the compressor wouldn't engage. I checked the fuse on the drivers side and it was fine. I checked the pressure switch and the pigtail and it was getting voltage.....bu t the pigtail to the compressor wasn't. So I checked the relay and it is toast. I jumped the pink to the green wire and clutch engaged.
The relay came in from Rockauto and AC clutch still doesn't turn on.
Here's what the voltage is at the relay plug...with the relay disconnected and car started
Relay plug
Pink with Black stripe 13.85-13.89 v
Dark Green .020 ( goes to compressor plug)
Green with yellow stripe 0 v
Blue 2.45V
Pressure switch (unplugged)
Light Green 3.30-3.33v
Blue 0v (as it is unplugged)
With the pressure switch completed both sides of switch have 3.30-3.50 Volts
Ac compressor wiring ( with ignition on only) and relay plugged in
Green - 0.10v
Black - 0.01
I have no idea what is going on. When i jump the pink and green wire on ac switch relay plug the compressor clutch engages and than eventually starts a small squeal and than after a couple engagements of me disconnecting jumper and connecting 12v the clutch engages but doesn't spin with pulley This is what was happening with my previous ac compressor and clutch as well and I though the clutch was bad. After this happening to the new compressor it's something entirely different.
Update the squeel is gone after I changed the ac compressor harness with diode with a new replacement..i jist jumped the relay pigtail.
So I ordered the relay and that didn't help. I also ordered the correct R134 Pressure Switch and that didn't help.
I even got another ECM and swapped my Prom and TT chip and still no dice.
My old relay and the new relay just click away until I turn off the power at the Digital Climate box......does it when it's set to hi 65 heater option....no clicking on Auto at 65 hi.
I have scoured years of post in regards to this issue and still no luck. I have used my multimeter and followed the tech pages on GNTtype and the other forums. I have checked the power at the harnesses of the heater module (New from Kirbans)...there us 12volt present at the brown 5 pin Harness. There is the light blue wire from pin B8 that splits off into 2. I have jumped the pressure switch and nothing. When I jump the pink/black wire amd the green wire the clutch engages. I have pulled out the Digital Climate Control Unit and checked voltage at the 3 connectors and the different wires as per the instruction on the diagnosis writeups from the factory manual and everything seems to be in working order. I have checked all the Fuses under the dash and all are good...none are burnt out.
My big question is what triggers the B8 pin to energize and send 12v through the green wire to the Compressor Clutch.
Is there any other fuse or relay that I am missing somewhere? The 85 Ac Compresser only has 1 pigtail as ther eis no high pressure switch or factory electric fans. I replaced rhe pigtail wirh the green and black wire with a new one with diode...thinki ng that it was faulty.
The compressor is new and has been filled R134, the system has been tested and has full vaccum...no leKs anywhere.
Please if anyone has had a similar issue throughout there time with there car please send me any info.
Thanks Am