No signal to A/C compressor relay

2010 CADILLAC ESCALADE
132,000 MILES • 6.2L • V8 • 2WD • AUTOMATIC
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DARKFREELIFE
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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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Sep 2, 2019 at 1:29 PM
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DARKFREELIFE
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Also forgot to mention the A/C pressure has been replaced 2 times.
Sep 2, 2019 at 1:33 PM
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ASEMASTER6371
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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
Sep 2, 2019 at 1:39 PM
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DARKFREELIFE
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Let me check real quick.
Sep 2, 2019 at 1:41 PM
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ASEMASTER6371
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Okay.
Sep 2, 2019 at 1:44 PM
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DARKFREELIFE
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Okay, key on I have 12 volts on pin 30 but nothing on 85.
Sep 2, 2019 at 1:46 PM
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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

Sep 2, 2019 at 1:50 PM
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DARKFREELIFE
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What wire do i check on pressure sensor? do i check with the car and A/C running?
Sep 2, 2019 at 1:50 PM
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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
Sep 2, 2019 at 1:51 PM
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DARKFREELIFE
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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.
Sep 2, 2019 at 1:51 PM
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DARKFREELIFE
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do I have to replace the whole fuse block or there is individual block inside the main block?
Sep 2, 2019 at 1:53 PM
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ASEMASTER6371
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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
Sep 2, 2019 at 1:55 PM
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DARKFREELIFE
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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.
Sep 2, 2019 at 2:02 PM
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ASEMASTER6371
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Okay, Give me the high and low side pressures.

Roy
Sep 2, 2019 at 2:04 PM
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DARKFREELIFE
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i did that and a P0690 came up with check engine light.
Sep 2, 2019 at 2:10 PM
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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.
Sep 2, 2019 at 2:12 PM
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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
Sep 2, 2019 at 2:19 PM
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DARKFREELIFE
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I did because when i jump pin 30 and 85 bits still not working. Now if jumping the relay low is 34 .
Sep 2, 2019 at 2:21 PM
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DARKFREELIFE
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Jumping pin 30 and 85 did not engaged the compressor.
Sep 2, 2019 at 2:22 PM
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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
Sep 2, 2019 at 2:23 PM
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ASEMASTER6371
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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
Sep 2, 2019 at 2:25 PM
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DARKFREELIFE
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Okay, something is wrong with power off keys out relay clicks and compressor engages, but when I turn the key on relay loses power and compressor disengages. Is there a chance I'm doing the wrong pins on the relay? If I hold is this direction pins 30 and 85 are at the bottom but if I hold the opposite way they are on top?
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Sep 2, 2019 at 2:30 PM
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ASEMASTER6371
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You will need an ohmmeter to check for the pin. One end at the compressor and one at the relay. Look for 0.00 ohms.

Roy
Sep 2, 2019 at 2:33 PM
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DARKFREELIFE
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Okay, check did it and still not working. what the voltage i should be getting on the pressure switch?
Sep 2, 2019 at 3:29 PM
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DARKFREELIFE
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One thing i forgot to mention that wiring diagram i found only is for a 2009 Escalade and mine is a 2010 i am guessing they are still the same?
Sep 2, 2019 at 3:33 PM
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ASEMASTER6371
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Yes, what about the relay? Let us do one thing at a time. Your issue is at the relay.

Roy
Sep 2, 2019 at 3:45 PM
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DARKFREELIFE
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Okay, this is what i did and noticed when I jump pin 30,85 relay clicks like it supposed to, but one i turn the car on the car it disengages. I did noticed pin 86 it is switching depending if car is on or off. when car is off I get 5 volts on pin 86 and it clicks, once I turn it on I get 12 volts and the relay no longer energized. that's the wire that comes from the EMC and it is grounding the relay like you said right?
Sep 2, 2019 at 3:46 PM
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DARKFREELIFE
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Okay, i replaced the relay with the fog lights which is the same and still nothing.
Sep 2, 2019 at 3:48 PM
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ASEMASTER6371
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There should be no voltage to pin 86 with the relay out.

It gets voltage from pin 85 when the fuse block sends the voltage.

I am afraid with your jumping and if you applied 12 volts to 85 to the PCM, you have damaged the PCM.

Roy
Sep 2, 2019 at 3:51 PM
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ASEMASTER6371
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You are still not sure if you installed it incorrectly. That is why you need to do the test I told you.

Roy
Sep 2, 2019 at 3:53 PM
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DARKFREELIFE
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Okay, let me explain my self more clearly I took some pictures. This is with the car off.
When relay is out on lin 86 dos not get any voltage. But as soon as I put the relay then it click and pin 86 get a feedback voltage of 5 volts. First picture is pin 30 and 85 I get 12 volts. I do have a spare ECM switch I just bought.
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Sep 2, 2019 at 4:04 PM
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DARKFREELIFE
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does this look good or the PCM is fried?
Sep 2, 2019 at 4:15 PM
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ASEMASTER6371
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My last answer did not post.

The 5 volts you see is not a feedback, it is a voltage drop between the relay and the PCM.

This sounds like a wiring problem between the relay and the PCM.

Roy
Sep 2, 2019 at 4:22 PM
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DARKFREELIFE
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Okay, what do you recommend? putting new PCM and risking getting messed up?
Sep 2, 2019 at 4:28 PM
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ASEMASTER6371
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You need to repair the wiring from the relay to the PCM. This is not a PCM issue. At least we are not there yet.

You need a fuse box and wiring repair to start.

Roy
Sep 2, 2019 at 4:30 PM
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DARKFREELIFE
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should i wait to get the new fuse block before installing new PCM?
Sep 2, 2019 at 4:31 PM
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ASEMASTER6371
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Forget about the PCM for now and do the items needed that we discovered.

Roy
Sep 2, 2019 at 4:33 PM
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DARKFREELIFE
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my question now is, how did wiring got messed up it was working fine three weeks ago?
Sep 2, 2019 at 4:34 PM
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DARKFREELIFE
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Okay, first thing is a new fuse block, right?
Then what would be the second step.
Sep 2, 2019 at 4:39 PM
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ASEMASTER6371
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It could have been working yesterday. There could be corrosion or broken wiring internally..

There is no warning when they fail.

Roy
Sep 2, 2019 at 4:40 PM
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DARKFREELIFE
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Okay, will do I will come back when parts get here.
Sep 2, 2019 at 4:42 PM