2003 Chevy Tahoe AC

Tiny
KURT_S_37
  • 2003 CHEVROLET TAHOE
  • V8
  • 4WD
  • AUTOMATIC

Need AC Wiring Diagram for 2003 Chevy Tahoe Compressor not cycling.
Has refrigerant. Need to trouble shoot the control circuitry.

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Monday, July 18th, 2011 AT 4:52 PM

12 Replies

Tiny
JDL
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At the compressor relay, terminal 30 is hot/voltage all the time. Terminal 86 goes hot with the key on. Terminal 85 is ground for the coil side of relay, controlled by the pcm. When the relay is energized, that line with the arrowhead, moves to terminal 87, that circuit carries voltage to ac compressor. At the ac compressor, dark green wire is voltage, black is ground. You have to have both.

You might be ahead to check for hvac trouble codes. Might need to know the pressures on the gauges. The low and high side have sensors that can keep the compressor from engauging. The high side sensor is on the high side hose in between the evaporater and condensor. Jump across the 2 wire sensor to see if the clutch engauges

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Monday, July 18th, 2011 AT 7:49 PM
Tiny
KURT_S_37
  • MEMBER

By passed the pressure switches first thing.
Still no compressor engagement.
Will proceed with further troubleshooting this evening with
the info gathered from here, and elsewhere on the web, and
get back to you with further queries, or, (hopefully) resolution
of my problem.

Thank you for your quick responses.

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Monday, July 18th, 2011 AT 9:00 PM
Tiny
JDL
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Let everybody know what you find.

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Monday, July 18th, 2011 AT 9:06 PM
Tiny
KURT_S_37
  • MEMBER

Finally got to do some more testing on the Tahoe A/C system.
(My daughter-in-law drives it and between work, school and three teenage granddaughters, it spends most of its time on the road. )

Was able to verify clutch operation and wiring to the underhood relay.
Triggering the relay with a lead connected to 12-v brings the compressor on line and the system starts cooling.

Still cannot get a signal on the control line from the interior.
(This with the pressure switch bypassed. - Btw, I checked the pressure switch with a meter and it tests good.)

Looks like I still need a diagram of the control circuitry in the dash.

This Tahoe does not have the 'Climate Control' version, it is the manual control system.

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Thursday, July 28th, 2011 AT 3:50 PM
Tiny
JDL
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Here you go, below. The computer grounds the coil side of ac clutch relay.

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Thursday, July 28th, 2011 AT 6:11 PM
Tiny
KURT_S_37
  • MEMBER

Thank you sir!

Need clarification on connector B3.
Image split through that one with no color or function visible on the second part.

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Thursday, July 28th, 2011 AT 8:33 PM
Tiny
JDL
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Sorry about that. Below is manual ac.

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Thursday, July 28th, 2011 AT 8:46 PM
Tiny
JDL
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Splitting the diagram is the only way I could do it and make it readable. The top diagram was for automatic ac. Whichever you have.

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Thursday, July 28th, 2011 AT 8:49 PM
Tiny
KURT_S_37
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Could you give me a bit more of the diagram?
Another problem it has is no fan on Hi, just the lower speeds.
Where does the Hi (#5) lead connect?
There must be a voltage divider there somewhere but I have no color code for the leads and am not sure where it is located.
If this is a really big file, could you send it to my email easier?
I can zoom and crop to suit on my own.

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Thursday, July 28th, 2011 AT 10:02 PM
Tiny
JDL
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Sorry, I can't do any better on the diagrams. Some of the large libraries carry automotive databases, if you live in the area they serve, the info is free. One of their databases, you access on your home computer. The other database is mitchel and you have to go to the library to access. It's all free, if you live in an area they serve. You can pay a small yearly fee to access alldata or mitchel for a single vehicle.

Below is wiring for blower speeds, manual ac. When the relay is energized, that little arm with the arrowhead, switches to terminal 87, carries voltage to blower motor for high speed only. When relay is not energized, the arm is on 87a, has continuity for lower speeds, only.

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Friday, July 29th, 2011 AT 5:22 PM
Tiny
KURT_S_37
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Thanks much.
Would never have found the direct link to the relay.
This explains why the lower speeds work while the Hi does not.

Should be able to solve all the problems w/ Ms Tahoe this week end.
If I can catch the daughter in law during one of her pit stops, that is.

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Friday, July 29th, 2011 AT 6:59 PM
Tiny
JDL
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If you can only work on it intermittently, hard to track it down. Good luck.

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Friday, July 29th, 2011 AT 7:13 PM

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