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.
have the same problem?
Monday, April 14th, 2014 AT 3:08 PM