How much refrigerant is needed to kick the ac clutch on for an empty system?

[hoffa65]

I don't want to muddy the thread with disagreement, but I think you may have stated this backwards. "Normally" is at rest and not energized.
https://www.galco.com/comp/prod/relay.htm
If we're both referring to the diagram on page 3, that's normally open. If we're talking about a different diagram I'll have to go back and look.
If the brown wire is neither grounded or shorted to power, it's actually a normally closed relay -- which is good because then 565 doesn't need to do anything. It could also be a NO relay that's just stuck in the closed position. Either way, if power goes through it to the clutch, that's just like having no relay and if we all pretend it isn't there, the system will function like an "old" car.

my bad you are correct. I always get that back asswards LOL you think Id get it after all these year in my business

It's a NO relay so it needs to be grounded to close and provide 12v to clutch on green/blk wire 966

sorry for the confusion

 

[greggbruceauto]

so according to the wiring diagrams I looked up, (manual ac I am assuming, not automatic ac) you can bypass the ecm controlled realy from either lt green wire to lt green/black -- that runs power through the ac clutch, then to the low pressure switch, which when unplugged, should now have juice on one side. The switches, in my experience vary somewhat, but should close above 28 psi and that would then turn on the clutch. So the switch is AFTER the clutch. IF you have a good ground on the other side of the switch, and the clutch is not bad, the compressor should turn on. You could always also jump between the switch terminals for a short second to see if the clutch kicks on.... but most GM's of that vintage won't turn on the compressor below 28 psi... (20 years in a GM dealer, here)

 

[DRIVEN]

No problem, figured you just typed it backwards. Only mentioned it in case someone digs the thread up in the future who is new to NO/NC.

565, you got that thing cut out and blowin' ice cubes yet?

 

[DRIVEN]

so according to the wiring diagrams I looked up, (manual ac I am assuming, not automatic ac) you can bypass the ecm controlled realy from either lt green wire to lt green/black -- that runs power through the ac clutch, then to the low pressure switch, which when unplugged, should now have juice on one side. The switches, in my experience vary somewhat, but should close above 28 psi and that would then turn on the clutch. So the switch is AFTER the clutch. IF you have a good ground on the other side of the switch, and the clutch is not bad, the compressor should turn on. You could always also jump between the switch terminals for a short second to see if the clutch kicks on.... but most GM's of that vintage won't turn on the compressor below 28 psi... (20 years in a GM dealer, here)

Yes. You are essentially removing all controlling components and hotwiring the system. Theoretically the cycling switch could be on either side of the clutch but in the diagram on page 3 it is on the ground side of the clutch.

 

[Texas82GP]

My vote is pull the relay and let the system function like an earlier car. The purpose of the relay is to allow the ECM to intervene in allowing the compressor clutch to energize. The ECM is no longer there so there really is no need to have the relay.

 

[565bbchevy]

I guess I should have put a voting poll up top.

 

[hoffa65]

My vote is pull the relay and let the system function like an earlier car. The purpose of the relay is to allow the ECM to intervene in allowing the compressor clutch to energize. The ECM is no longer there so there really is no need to have the relay.

Exactly

 

[greggbruceauto]

lol, that would be the simplest route -- yes the ecm was used to disable ac usually at WOT or an overheat condition --

 

[fleming442]

 

[69hurstolds]

Non destructive test suggestion- don't have to tear out anything but you can at least check to see if the clutch engages. Then, if you want to ground the brown wire and leave everything, fine. Or if you want to jumper the wiring permanently and get rid of the relay, you can do that too. Still have a choice.

TEST- Pull the plug to the relay. Find a green and green/black wiring. Put a temporary jumper wire across the plug into the wire socket. Since this is the only real wiring you'll be needing without the ECM, this should tell you if the clutch will engage when you turn the system to Norm or Max or whatever with the key on and enough pressure in the system to keep the cycling switch closed. If it doesn't, you got another issue to deal with.