A/C clutch not engaging, help with electrical diagnostic

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2005 SAAB
5.3L
V8
AWD
AUTOMATIC
85,000 MILES

This is a 2005 Saab 9-7x with the 5.3l V8 (Same drivetrain as GMC Envoy)
I'm having a issue with the A/C Clutch not responding to command, yet the clutch can be Power Probed to work. I have run thru the wiring diagram and followed every instruction to the end, yet the ECM is not sending a command to the A/C relay. I've triple checked all the wiring for open or shorts and have not found any to the best of our ability however we are thinking that we must have missed something. I've checked all fuses. I've checked all continuity within the circuit and everything is good. I've replaced the HVAC control module. I've replaced the ECM. It was flashed by the parts warehouse and the anti-theft relearn performed by us. I've checked the system for leaks and proper charge and that is good. I've followed the AllData process step by step and I'm stumped. The low pressure switch when jumped does not activate the A/C clutch. Just to be certain we replaced the low pressure switch. The A/C relay has been swapped with several known good ones and that has not solved the issue. Without a command signal the A/C will not engage. I've explored all amibient temp. Sensors. I've even pulled the fuse box apart under the hood and inspected each contact for continuity and no issues all checked good. I've checked all connections which all the grounds and power wires go through. I have not preformed any voltage drop test, only because I am still uncertain of that procedure and was not directed to do so in the procedures or step by step diagnoistics. I'm pulling my hair out trying to find a solution. I almost want to condemn the A/C Clutch for a bad ground and the ohms test showed bad, but when I power it up independant it works. We have a new AC compressor standing by and it bench tests the same as the currently installed unit.

We are using the Power Probe 3 which is new to us and also the autel Maxidas DS708 Scan tool which is also new to us. We are getting feedback from all sensors and all commands are being recognized from the HVAC module which is a new unit that we replaced. In the Autel diagnostics I am seeing a "A/C compressor feedback" which is indicating NO Feed back or Incomplete. However I don't know if that is relevant since the compressor is not engaged when commanded.

Here is what we know for certain. The command from the relay is not getting to the compressor. The problem seems to be in the 4 pronged circuit of the relay.

Circuit 30 has power
Circuit 86 has power
Circuit 87 shows open
circuit 85 shows 0.00

This is with Key On Engine Off

According to AllData we are supposed to verify that a test lamp illuminates between the ignition circuit terminal 85 and ground. However it did not.

Can you describe in laymens terms how to test the ignition circuit for a short to ground or open/high resistance. (If you know how to do the test with the power probe 3 that would be fantastic)

If you review Alldata for this vehicle it will give the diagnostic troubleshooting which we followed step by step.

We believe it is a short or open somewhere in the circuit path but we are just getting lost with over 2 weeks of trial and error testing we are getting confused with all the different tests we have performed to date. We do have extensive wiring diagrams through alldata and haynes manuals as well as having isolated the circuits and wires we are working with to the best of our knowledge. Just to make a point we have combined 30+ years in the industry and have consulted other local master mechanics and this has all of us stumped. But we most certainly do not specialize in electrical issues which is why we are probably having some difficulties.

A donation of $10 is yours regardless if you can help but if you can solve this mystery then we will most certainly give a larger and more generous donation.

Any insights would be helpful.
A contact Phone number is 302-373-9754
Respectfully, Dan & Josh Menefee, Great Cars by Maranatha Motors Inc.

11 Replies

HMAC300

MECHANIC
48,601 POSTS

If this is auto temp control which I think it is you have to scan it to see which sensor inside the car is screwing up not allowing your compressor to kick on. Testing with power probe doesn't do any good ifyou have a bad sensor or sund load sensor etc. So find that out first.

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Tuesday, April 15th, 2014 AT 6:16 AM

HMAC300

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One other thing I forgot to mention the hvac module needs to be programmed to the vehicle as well if you didn't do that then that may be the problem as well.

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Tuesday, April 15th, 2014 AT 6:33 AM

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Yes it is a automatic system.

Q. Dosen't the Defrost Cycle over ride any sensor in the vehicle?

I was told that in defrost mode the system defaults to on for clearing the windows and such. This mode should cancel out sunload and ambient temp sensors, this was my concern as well, but was dismissed by other tech I am working with.

As far as the relearn procedure for the module we did this. It was a start simple process of key on engine running for 60 sec. With no loads and no commands for unit, as per scan tool.

The HVAC responds to all commands and request and recognizes the request for A/c.

I will review the information again.
Any other thoughts on the matter would be appreciated.
Thanks,
Dan

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Tuesday, April 15th, 2014 AT 7:50 AM

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We also had previously replaced the Sunload Sensor with a new factory.

But we will double check it since parts can be defective right out of the box.

Dan

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Tuesday, April 15th, 2014 AT 8:03 AM

HMAC300

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48,601 POSTS

1Did you perform the Diagnostic System Check-Vehicle?-Go to Step 2 Go to Diagnostic System Check-Vehicle
to Start the engine.
Set the parking brake.
Place the vehicle in drive and allow the engine to idle.
Observe the engine RPM.
Does the engine idle at a steady RPM?-Go to Step 3 Rough, Unstableor Incorrect Idle and Stalling for the 4. Tool engine
3 Start the engine.
Observe the coolant temperature indicator.
Is the engine coolant temperature indicator illuminated?-Go to Engine Coolant Temperature Indicator Always On Go to Step 4
Observe the coolant temperature indicator.
Is the engine coolant temperature indicator illuminated?-Go to Engine Coolant Temperature Indicator Always On Go to Step 4
4 Install a scan tool.
Turn ON the ignition, with the engine OFF.
Using a scan tool, observe the A/C Switch parameter in the Heating and Air Conditioning data list while pressing the A/C request switch.
Does the A/C Switch parameter change states when the A/C request switch is pressed?-Go to Step 5 Go to Step 26
5 IMPORTANT:
For A/C compressor operation, the ambient air temperature display must be above 1°C (35°F).

Refer to Ambient Air Temperature Update Procedure.
Start the engine.
Place the blower motor switch in the maximum speed position.
Place the A/C request switch in the ON position.
Place the left air temperature switch in the coldest position.
Does the A/C compressor clutch engage?-Go to Testing for Intermittent Conditions and Poor Connections Go to Step 6
6 Park the vehicle inside or out of direct sunlight.
Open the window in order to ventilate the interior of the vehicle.
Turn OFF the ignition.
If the A/C system was operating, then wait for approximately 2 minutes.
Install J 43600 ACR 2000 Air Conditioning Service Center.
Record the ambient temperature at the vehicle.
Record readings of the low and high side STATIC pressures.
Compare the low and the high side pressure values with the allowable limits for the recorded ambient air temperature.
Are the low and the high side pressure values within the allowable limits for the recorded ambient air temperature? Are the pressure values within 103 kPa (15 psi) of each other?Above 16°C (60°F) 345 kPa (50 psi)
Above 24°C (75°F) 483 kPa (70 psi)
Above 33°C (90°F) 690 kPa (100 psi) Go to Step 7 Go to Leak Testing
7Start the engine.
With a scan tool, observe the A/C Permission parameter in the Heating and Air Conditioning data list.
Does the A/C Permission parameter display Granted?-Go to Step 14 Go to Step 8
8 Turn the ignition OFF.
Turn ON the ignition, with the engine OFF.
With a scan tool, observe the Pressure Cycle Switch parameter in the Heating and Air Conditioning data list.
Does the Pressure Cycle Switch parameter display Normal?-Go to Step 12 Go to Step 9
9 Turn OFF the ignition.
Disconnect the A/C low pressure switch.
Turn ON the ignition, with the engine OFF.
Connect a 3-amp fused jumper between the signal circuit and the ground circuit of the A/C low pressure switch.
Observe the Pressure Cycle Switch parameter in the Heating and Air Conditioning data list.
Does the Pressure Cycle Switch parameter display Normal?-Go to Step 23 Go to Step 10
10Test the signal circuit of the A/C low pressure switch for a high resistance or for an open. Refer to Circuit Testing and Wiring Repairs.
Did you find and correct the condition?-Go to Step 35 Go to Step 1
11Test the ground circuit of the A/C low pressure switch for a high resistance or for an open. Refer to Circuit Testing and Wiring Repairs.
Did you find and correct the condition?-Go to Step 35 Go to Step 26
12 With a scan tool, observe the A/C High Side Pressure parameter in the Powertrain data list.
Is the parameter less than the specified value? 2, 413 kPa (350 psi) Go to Step 26 Go to Step 13
13Turn OFF the ignition.
If the A/C system was operating, then wait for approximately 2 minutes.
Install the J 43600.
Turn ON the ignition, with the engine OFF.
With a scan tool, observe the A/C High Side Pressure Sensor parameter in the Powertrain data list.
Compare the A/C high side pressure on the scan tool to the high side pressure on the J 43600.
Are the high side pressure values within 103 kPa (15 psi) of each other?-Go to Air Conditioning (A/C) System Performance Test Go to Step 24
14With a scan tool, observe the A/C Compressor Feedback parameter in the Heating and Air Conditioning data list.
Does the A/C Compressor Feedback parameter display On?-Go to Step 15 Go to Step 16
15Test the ground circuit of the A/C compressor clutch for a high resistance or for an open. Refer to Circuit Testing and Wiring Repairs.
Did you find and correct the condition?-Go to Step 35 Go to Step 25
16Start the engine.
With a scan tool, command the A/C Permission to Granted and Withheld.
Does the relay turn ON and OFF with each command?-Go to Step 17 Go to Step 19
17Turn OFF the ignition.
Test the battery positive voltage circuit of the A/C compressor clutch relay for a high resistance or for an open. Refer to Circuit Testing and Wiring Repairs.
Did you find and correct the condition?-Go to Step 35 Go to Step 18
218Test the supply voltage circuit of the A/C compressor clutch for a high resistance or for an open. Refer to Circuit Testing and Wiring Repairs.
Did you find and correct the condition?-Go to Step 35 Go to Step 22
19Turn OFF the ignition.
Disconnect the A/C compressor clutch relay.
Turn ON the ignition, with the engine OFF.
Probe the ignition 3 voltage circuit of the A/C compressor clutch relay with a test lamp that is connected to ground.
Does the test lamp illuminate?-Go to Step to Go to Step 28
20Start the engine.
Connect a test lamp between the control circuit and the ignition 3 voltage circuit of the A/C compressor clutch relay.
With a scan tool, command the A/C Permission to Granted.
Does the test lamp illuminate?-Go to Step 22 Go to Step 21
21Turn OFF the ignition.
Test the A/C compressor clutch control circuit of the powertrain control module (PCM) for a high resistance or for an open. Refer to Circuit Testing and Wiring Repairs.
Did you find and correct the condition?-Go to Step 35 Go to Step 27
Turn OFF the ignition.
Test the A/C compressor clutch control circuit of the powertrain control module (PCM) for a high resistance or for an open. Refer to Circuit Testing and Wiring Repairs.
Did you find and correct the condition?-Go to Step 35 Go to Step 27
22Turn OFF the ignition.
Inspect for poor connections at the A/C compressor clutch relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs.
Did you find and correct the condition?-Go to Step 35 Go to Step 29
23Inspect for poor connections at the harness connector of the A/C low pressure switch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs.
Did you find and correct the condition?-Go to Step 35 Go to Step 30
24Inspect for poor connections at the harness connector of the A/C refrigerant pressure sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs.
Did you find and correct the condition?-Go to Step 35 Go to Step 31
25Inspect for poor connections at the harness connector of the A/C compressor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs.
Did you find and correct the condition?-Go to Step 35 Go to Step 32
26Inspect for poor connections at the harness connector of the HVAC control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs.
Did you find and correct the condition?-Go to Step 35 Go to Step 33
27Inspect for poor connections at the harness connector of the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs.
Did you find and correct the condition?-Go to Step 35 Go to Step 34
28Repair the ignition 3 voltage circuit of the A/C compressor clutch relay. Refer to Wiring Repairs.
Did you complete the repair?-Go to Step 35-
29Replace the A/C compressor clutch relay.
Did you complete the replacement?-Go to Step 35-
30Replace the A/C low pressure switch. Refer to Air Conditioning (A/C) Low Pressure Switch Replacement.
Did you complete the replacement?-Go to Step 35-
31Replace the A/C refrigerant pressure sensor. Refer to Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement.
Did you complete the replacement?-Go to Step 35-
32Replace the A/C compressor. Refer to Compressor Replacement (LM4) or Compressor Replacement (Late).
Did you complete the replacement?-Go to Step 35-
33Replace the HVAC control module. Refer to Control Module References for replacement, setup, and programming.
Did you complete the replacement?-Go to Step 35-
34Replace the PCM. Refer to Control Module References for replacement, setup, and programming.
Did you complete the replacement?

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Tuesday, April 15th, 2014 AT 8:09 AM

HMAC300

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The lst reply covers majority of steps to find the problem could be a pcm not turning it on or a poor connection there.

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Tuesday, April 15th, 2014 AT 8:10 AM

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We followed Alldata test procedures which were very closely related to all of the above.

Is your information from Mitchell on demand?

Some of it is different, but the basics have been covered

We have isolated the issue to the dark green/white wire from ECM leading to the ignition circuit pin 85 of the A/c relay.

Without this signal the relay is unable to command on the A/C clutch.

We have tested the A/C clutch with power probe and it engages and runs with the car on and with key in the on position only.

We are getting readings from all ambient temp sensors on the scan tool.

If you have access to Alldata on demand and you can review the wiring diagrams for the HVAC system this might help in understanding the systems wiring path. A quick review could possible shed some light on the issue.

Thanks for the information, some of which ran on together and a bit hard to dissect.

The "Diagnositics System Check-Vehicle" process was not outlined to the best of my knowledge in the overview that I followed.

Is this a step that is covered in the scan tool or is it part of the relearn for the HVAC control module relearn?

We seem to be getting closer to the issue, but not for certain.

BTW, I did mention that we have installed a remanufactored ECM that was flashed by the Parts Warehouse and then we followed the 30 min. Manual re-learn procedure.

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Tuesday, April 15th, 2014 AT 1:26 PM

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We inspected all connections at ECM, HVAC, and Underhood Fuse Box, as well as connections and grounds at engine block, radiator support, rear fire wall, and the A/C compressor. All were tight and continuity checks were done for all wires leading to compressor and fuse box. We also did continuity check of dk gr. / White wire and that was good.

I have begun to question a bad ECM, but the issue is the same with the old as the new.

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Tuesday, April 15th, 2014 AT 1:32 PM

HMAC300

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That wire leads from pcm. So with a/c turned on probe from pcm and see if it gets power if it does then it's a short between pcm and relay if not probe the other wire then probe the ight green at compressor to see if hvac is sendingpower as well. I kinda think you either have abad connection or broken wire someplace along there. Cour it doesn't mean that a pcm is good either even if it's been replaced.

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Tuesday, April 15th, 2014 AT 1:54 PM

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Solved the issue. It was the compressor after all.

One detail that was left out was that the engine had to be running for the ECM to command ON the Compressor On.

As a result the compressor was not receiving a signal.

Without the signal all my test results were false and misleading

The signal only originates from a vehicle that is running with a proper voltage reading above 12.5

The Hvac Module was showing a command sent in the key on engine off position.

I ended up taking it to an independent shop who had it figured out in short order after I explained all my steps.

I was sure that I had run this test with the vehicle running many times, but who knows. My extensive notes showed at least several running test of the system and the voltage was not present at the relay at any of the test I made. I could not explain why it didn't work for me.

The exact cause of the failure was the internal high pressure cut off, within the A/C compressor, was shorted out.

The original ECM is back in the vehicle.

Tomorrow we will install the new compressor, a dryer, new orifice, seals, then pull vacuum for 30 minutes, and then recharge the system.

The crazy thing that kept me from failing the compressor was the fact that when I Power Probed the AC Compressor, the Clutch engaged and worked.

The problem was the internal high pressure cut off switch was fried.

Most likely happened when the blower resistor went. Which was the original problem to begin with. I failed to mention that but thought it unrelated to the issue at hand.

Thanks for your input
Dan

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Wednesday, April 16th, 2014 AT 9:07 PM

HMAC300

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The high pressure switch only fires when it gets to high and a resistor wouldn't cause that make sure to check for a blockage at orfice as the compressor may have blown one of the valves and blocked the orfice causing the high pressure.

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Thursday, April 17th, 2014 AT 6:51 AM

A/C clutch not engaging, help with electrical diagnostic

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