Help! AC Clutch Engages only when Jumped to the Battery - Mercedes-Benz Forum

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post #1 of 3 (permalink) Old 08-16-2006, 09:56 AM Thread Starter
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Help! AC Clutch Engages only when Jumped to the Battery

I've been trouble shooting my AC system for a few weeks now. I finally was able to figure out that the AC compressor & clutch were working, the system had gotten low on freon and shut itself off. So I was able to jump the compressor to fill the system with freon, which is now reading at about 40PSI. Now I am stumped. I'm at the point where the AC clutch engages only when it is jumped to the battery terminal, when I do this I have nice and cold AC. But the clutch doesn't engage when I put the AC on in the car or the defrost like it should. I've checked all the fuses and they appear to be fine. I've tried to disconnect the battery to reset the computer in case the computer still had an error reading low pressure. And still nothing. Any suggestions?
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post #2 of 3 (permalink) Old 08-16-2006, 11:33 AM
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40 psi in the system to start with is way to low.
The pressure suppose to be checked with the compressor running and the low side suppose to stay at least 35 psi.
I believe high side goes to about 240 psi, but check this with manufacturer site.
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post #3 of 3 (permalink) Old 08-16-2006, 11:43 AM Thread Starter
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Thanks for the information. I did check the low pressure side and that is what was reading 40 psi. But I'm not sure if that was checked when the car was running. I will re-check that. Where can I locate the high pressure port?
At what point will the compressor disengage when the pressure gets too low in the AC system? When enough pressure is put back into the system will the compressor begin to engage as it is supposed to? Or do you have to reset the system somehow?
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