2010 GL450 AC Issues
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2010 GL450 AC Issues
Hi all! 2010 GL450, the AC compressor locked up and sheared like it's supposed to. We have evacuated the system, changed the compressor, vacuumed the system and during the recharge, just cannot get the compressor back on. A quick stop at the local shop identified a potential short or open (for some reason didn't specify which) in the compressor control circuitry, as noted on a snapon scanner. We have since been able to (without knowing how) have compressor engage and was able to finish charging with refrigerant. I was back-probing the connector to the compressor to watch voltage as engine RPM increased, expecting to see 14v become 13, or 10, or 6, because of variable displacement but it stayed 14ish. High side pressure ran up to like 350psi and compressor got kicked offline, with voltage at the connector now showing 0V, understandably. We can't get compressor voltage consistently, and when it does come on, it doesn't seem to be regulating itself.
So what controls the duty cycle so that this variable displacement compressor is truly variable?
Another observation is the electric cooling fan doesn't come on with request of AC, but when we DO manage to get the compressor on, the Fan also comes on. Perhaps A funky fan circuit/component is also keeping the compressor from coming on?
Anybody wanna take a stab? 🙃
So what controls the duty cycle so that this variable displacement compressor is truly variable?
Another observation is the electric cooling fan doesn't come on with request of AC, but when we DO manage to get the compressor on, the Fan also comes on. Perhaps A funky fan circuit/component is also keeping the compressor from coming on?
Anybody wanna take a stab? 🙃
Senior Member
Joined: Jan 2017
Posts: 254
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From: Houston, TX
Mercedes Benz 2007 GL450 , 2012 BMW 528i
Basically you put a shottky diode between compressor signal wire and ground, to prevent error 9006 by preventing current going back to ground. Just run a search on this forum and you will find a long thread. Let me know if you can't find it and i will search and link it in here.
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Basically you put a shottky diode between compressor signal wire and ground, to prevent error 9006 by preventing current going back to ground. Just run a search on this forum and you will find a long thread. Let me know if you can't find it and i will search and link it in here.
Would this also perhaps make the 'computer' act more user friendly with solenoid and restore full functionality? And actually vary voltage to the solenoid like it should. I should be able to solder this sucker on tomorrow.
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UPDATE: I am happy to report the "diode fix" solved my issue. For anyone else not sure what this means, Google "mercedes 9006 error AC" or something like that. Get you a diode and install it like the instructions show. Or... buy a genuine compressor OR a genuine variable solenoid and install it in your aftermarket compressor hehe.
Senior Member
Joined: Jan 2017
Posts: 254
Likes: 60
From: Houston, TX
Mercedes Benz 2007 GL450 , 2012 BMW 528i
UPDATE: I am happy to report the "diode fix" solved my issue. For anyone else not sure what this means, Google "mercedes 9006 error AC" or something like that. Get you a diode and install it like the instructions show. Or... buy a genuine compressor OR a genuine variable solenoid and install it in your aftermarket compressor hehe.
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What I did was use the little harness from the old compressor (so I could solder on my workbench instead of under the vehicle). The Diode goes between the Red and Black wires of the comressor harness. Once the harness was modified and wrapped up safely, I swapped it with the harness of the new compress which was already installed and charged. Since I couldn't get access to the bolt that holds the ground ring terminal, I relocated the ground to the bolt that holds the clamp for the harness, since i was able to access it (again, the compressor is already installed). Ops check went all good, compressor works as it should now, and I have an appt to have the refrigerant evacuated one last time, then refilled by weight with a proper machine, since we charged with refrigerant cans - I'm sure the charge level is likely very close, but I'd feel better having it done by machine and measuring weight, since the compressor varies output so the pressures will be skewed because of that.
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