No voltage at AC clutch wire

454C2500

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So I installed my reman AC Delco compressor and tried everything I could to get the clutch wire on the truck to give the compressor 12V. At no point will it do that. I even put 2 cans into the system...clutch won't engage. AC light on controller just flashes. What a headache. Is there a way to force it other than to jump the clutch from the battery? Last time it needed refrigerant the clutch engaged after a can entered the system. What could be causing no voltage at the clutch wires?
 

1998_K1500_Sub

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What could be causing no voltage at the clutch wires?

Is the airgap so great that the clutch coil can’t engage the clutch?

Have you used an DVM to check the resistance on the coil to see that it is actually not open circuited?
 

454C2500

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Sorry I should have been more clear. I can engage the clutch no problem with a wire from battery. I don't have a high pressure switch on the compressor it seems. I don't see any wire that would go to one. I tried jumping the low pressure switch on the dryer and that didn't work to engage clutch. I am thinking maybe the relay behind the glove box maybe is to blame?
 

454C2500

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Oh also - unrelated but let me tell you this "reman" ac delco compressor is pretty noisy. I am almost positive I received a dud and it needs to go back.
 

1998_K1500_Sub

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Oh also - unrelated but let me tell you this "reman" ac delco compressor is pretty noisy. I am almost positive I received a dud and it needs to go back.

What model vehicle?

What was the condition of the orifice tube prior to initiating this repair?

What did you do to assure the proper amount of oil is in the system?

How much PAG (oz) did you put in the compressor upon installing?

How much PAG (oz) did you put in in the receiver / dryer?

What else was replaced during this repair? What has been replaced prior?

What was flushed?

How long was vacuum applied when evacuating the system? How deep was the vacuum (29.7”)? Did it hold vacuum for hours / days, after removing the vacuum pump?
 
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454C2500

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What model vehicle?

1992 454
What was the condition of the orifice tube prior to initiating this repair?
Replaced
What did you do to assure the proper amount of oil is in the system?
Measured
How much PAG (oz) did you put in the compressor upon installing?
Matched specs on 4 seasons pdf
How much PAG (oz) did you put in in the receiver / dryer?
Same thing
What else was replaced during this repair? What has been replaced prior?
I dont think anything recently
What was flushed?
Whole thing was flushed first
How long was vacuum applied when evacuating the system? How deep was the vacuum (29.7”)? Did it hold vacuum for hours / days, after removing the vacuum pump?
Vacuumed to damn near 30 and it held for a day or two. Doesn't really matter though because the compressor won't come on without a jump :sad:
 

1998_K1500_Sub

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(in reply to @454C2500's above)

OK, so regarding the noisy compressor, we have reason to believe:
- The oil volume in the system is proper
- The oil's not diluted with flush (it wouldn't have held a vacuum for long if it was)

These should not be factors, then, in the "noise" issue. But...

Was there any debris in the system before... was the prior orifice tube clean? If there was debris on the OT screen, was the condenser replaced too?

Back to the electrical "problem":

First and foremost, a DVM is your best friend and would give you answers in a jiffy.

Take a look at the AC Troubleshooting guide and related text from the 1989 service manual (I happened to have a copy handy). These may be relevant to your year.

There are service manuals available in .pdf form, here: https://www.gmt400.com/threads/88-95-service-manuals.43575/

Other, random thoughts:

What's that "flashing light" mean on the AC control?

Can you swap the relay, or jumper around it, and check for clutch operation?

Was the system demonstrating this "clutch won't energize" problem before?

In the course of repair, was anything done to cause this behavior, e.g.,
- the low-pressure cycling switch replaced with a new-but-failed unit?
- the wiring was strained somehow?
 

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