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No signal to A/C compressor relay

Tiny
DARKFREELIFE
  • MEMBER
  • 2010 CADILLAC ESCALADE
  • 6.2L
  • V8
  • 2WD
  • AUTOMATIC
  • 132,000 MILES
Long story short I have the car listed above and the A/C starting going out until it did not work anymore.

1. System has been flush and recharged.
2. Orifice and expansion valve has been replaced.

I have visited 4 different shops and nobody can find what's wrong with it.
the last shop said it was something electrical since the ECM was not sending power to the A/C pressure Sensor, so I went ahead and bout and reprogram a new ECM and nothing.

The bottom line is the compressor its not coming on but if I jump 30, 87 compressor comes right on with no problem. Looking at the electrical diagram the wire 63
dark green/white is the signal wire that supposed to command the relay to turn on and off?

I really don't know what to do anymore I really need some help.

I also was reading a similar thread here and one guy did everything swap lots of parts and it end up been the compressor? Will the compressor still be bad it it engages manually by jumping wires? Post stated he could manually jump compressor too and it will come on.
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Monday, September 2nd, 2019 AT 1:29 PM

52 Replies

Tiny
DARKFREELIFE
  • MEMBER
  • 36 POSTS
Also forgot to mention the A/C pressure has been replaced 2 times.
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Monday, September 2nd, 2019 AT 1:33 PM
Tiny
ASEMASTER6371
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  • 52,797 POSTS
Good afternoon,

Let us back up.

As for the relay, with the key on, do you have power at pin 30 and pin 85?

If you do, then the green/white is a ground for the control side. The PCM grounds the relay based on the input from the pressure sensor.

Can you check for voltage at the pressure sensor?

Roy
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Monday, September 2nd, 2019 AT 1:39 PM
Tiny
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  • 36 POSTS
Let me check real quick.
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Monday, September 2nd, 2019 AT 1:41 PM
Tiny
ASEMASTER6371
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Okay.
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Monday, September 2nd, 2019 AT 1:44 PM
Tiny
DARKFREELIFE
  • MEMBER
  • 36 POSTS
Okay, key on I have 12 volts on pin 30 but nothing on 85.
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Monday, September 2nd, 2019 AT 1:46 PM
Tiny
ASEMASTER6371
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Okay, that is your issue. There is no power to the control side.

The same wire that feeds pin 30 feeds 85. If there is no power, then the fuse block is the issue as that is what supplies power to that terminal.

Replace the fuse block.

I am very surprised that no one took the time to check this. This is a basic diagnostic.

Roy
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Monday, September 2nd, 2019 AT 1:50 PM
Tiny
DARKFREELIFE
  • MEMBER
  • 36 POSTS
What wire do I check on pressure sensor? Do I check with the car and A/C running?
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Monday, September 2nd, 2019 AT 1:50 PM
Tiny
ASEMASTER6371
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Do not worry about this yet. I think once you resolve the voltage issue at the relay, you will be good.

Roy
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Monday, September 2nd, 2019 AT 1:51 PM
Tiny
DARKFREELIFE
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  • 36 POSTS
Can I jump pin 30 and 85 of that won't work? It is really hot here in Texas and I really need my A/C.
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Monday, September 2nd, 2019 AT 1:51 PM
Tiny
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  • 36 POSTS
Do I have to replace the whole fuse block or there is individual block inside the main block?
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Monday, September 2nd, 2019 AT 1:53 PM
Tiny
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There is a common bus bar that feeds different terminals.

You need the whole fuse block.

Yes, you can jump it temporarily until you repair it correctly.

Roy
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Monday, September 2nd, 2019 AT 1:55 PM
Tiny
DARKFREELIFE
  • MEMBER
  • 36 POSTS
Okay, I just jump pin 30 and 85 I hear a click, but the compressor still does not come on. I will check for pressure no.
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Monday, September 2nd, 2019 AT 2:02 PM
Tiny
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Okay, Give me the high and low side pressures.

Roy
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Monday, September 2nd, 2019 AT 2:04 PM
Tiny
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I did that and a P0690 came up with check engine light.
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Monday, September 2nd, 2019 AT 2:10 PM
Tiny
DARKFREELIFE
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Static pressure on low 95 high 95. Jumping the relay low 50 high 250
the ambient temperature here in Texas is 97.
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Monday, September 2nd, 2019 AT 2:12 PM
Tiny
ASEMASTER6371
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Why are you jumping the relay? It should be working on its own now.

Low side is way high. It should be 30-35 lbs. 50 is flooding the evaporator and will not cool well at all.

Roy
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Monday, September 2nd, 2019 AT 2:19 PM
Tiny
DARKFREELIFE
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  • 36 POSTS
I did because when I jump pin 30 and 85 bits still not working. Now if jumping the relay low is 34.
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Monday, September 2nd, 2019 AT 2:21 PM
Tiny
DARKFREELIFE
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  • 36 POSTS
Jumping pin 30 and 85 did not engaged the compressor.
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Monday, September 2nd, 2019 AT 2:22 PM
Tiny
ASEMASTER6371
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You said you heard the relay click? Is that true? That means the relay energized. The compressor should have come online.

If it clicked and not turn on the compressor, replace the relay.

Roy
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Monday, September 2nd, 2019 AT 2:23 PM
Tiny
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It will not engage the compressor. It will provide power to the control side so the relay engages. You need to jump the pins and insert the relay with it jumped.

Roy
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Monday, September 2nd, 2019 AT 2:25 PM

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