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John, Master A.S.E Automotive technician
Category: Chevy
Satisfied Customers: 9176
Experience:  A.S.E MasterTechnician A1-A8 w/L1,38 years experience General Motors Master Technician
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2005 Malibu Classic: the air conditioner compressor to run..switches

Customer Question

2005 Malibu Classic's Air Conditioner Switch does not always energize to make the allow the air conditioner compressor to run. Also two other switches in the air conditioner control panel does not energize most of the time. Why?
Submitted: 6 years ago.
Category: Chevy
Expert:  John replied 6 years ago.

HelloCustomer

Most likely you have a faulty a/c control.This can be tested with a 12 volt test lamp & pull the control out of the dash & leave the harness connected.Back probe the wiring harness as you push the a/c control buttons.See if the circuit is powered up when the button is pressed.If not replace the a/c control.

Customer: replied 6 years ago.
The control panel was priced at a local dealer at $200.00 therefore I want to be sure I test correctly before I purchase a new control. To further explain the condition, none of the four switches on the control panel respond when depressed. The Fisrt switch 1)Flow
Thru Air switch stays lite constantly, the Second switch 2) Recirculate Air switch does not come on when depressed, the Third switch 3) Air Conditioner switch does not come on when depressed, and the Fourth switch 4) Rear Defrost switch does not come on when depressed. There are 8 wires in the switch control harness. Which two wires do I probe with the Light? If the light comes on does that indicate 12 volts? Does this circuit go to a relay and then to the AC compressor? The wires from the AC control switch looks too small to operate a compressors. Thanks for any more info.
Expert:  John replied 6 years ago.

Look at this closely,this is the plug to the a/c control head.Below are the wiring color & function.The sensor & door circuits must be tested with a volt meter,the other is marked.

 

Object Number: 73156  Size: CH

Pin

Wire Color

Circuit No.

Function

A1

RD/WH

440

Battery Positive Voltage 12 volts

A2

--

--

Not Used

A3

BN

141

Ignition 3 Voltage 12 volts

A4

--

--

Not Used

A5

D-GN

5060

Low Speed GMLAN Serial Data

A6

D-GN

5060

Low Speed GMLAN Serial Data

A7

GY/BK

754

Blower Speed Request Signal

A8

BN

404

Upper Air Temperature Sensor Signal

A9

L-GN

405

Lower Air Temperature Sensor Signal

A10

L-GN/BK

1647

Recirculation Door Control A

A11

TN

2273

Mode Door Control A

A12

D-BU

1199

Air Temperature Door Control A

B1-B2

--

--

Not Used

B3

GY

8

Instrument Panel Lamp Supply Voltage

B4

--

--

Not Used

B5

BK/WH

651

Ground

B6-B7

--

--

Not Used

B8

TN

470

Low Reference

B9

TN

476

Low Reference

B10

PK/WH

1648

Recirculation Door Control B

B11

L-GN

2275

Mode Door control B

B12

YE

1791

Air Temperature Door Control B

 

Customer: replied 6 years ago.
Thanks for the wiring color info. However, the wire colors on my 2005 Malibu are different colors. I measured the voltage to ground of each color while the engine was running and the fan "ON". For each color I depressed and released each of the four switches and recorded the voltage. The readings are as follows. White- 12, 12, 12, 12. Black/ White- 0,0,0,0. Green - 0,0,0,0. Orange- 12, 12, 12, 12, 12. Gray- 0,0,0,0. Dark Brown- 0,0,0,0.
Brown- 12,12,12,12. Blue - 2.5, 2.5, 2.5, 2.5. As you can see the voltages did not change when the switches were pushed and released. Is this information enough to know if the A/C Control Panel is faulty?
Expert:  John replied 6 years ago.
This sounds like the control head is dead.Make sure the ground at the control head is good.B5-test this for good ground & use it in your testing.B3 should be a variable voltage controlled by the instrument panel dimmer control.
John, Master A.S.E Automotive technician
Category: Chevy
Satisfied Customers: 9176
Experience: A.S.E MasterTechnician A1-A8 w/L1,38 years experience General Motors Master Technician
John and 10 other Chevy Specialists are ready to help you
Customer: replied 6 years ago.
All of your inputs together have enabled me to correct the problem. I disassembled the control and found a couple of questionable solder joints where the head is connected to the electronic control board. I fluxed these connection and resolded. Everything works fine now. I appreciate the very good input.
Expert:  John replied 6 years ago.

You deserve a gold star ! You have repaired a control head & did not just throw a part.This is the way we used to repair things when I started 40 years ago.I applaud you.I never know the ability of a person I am communicating with on line.I hope you have a great day.

John

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