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1991 Mercedes Benz 300SE
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Discussion Starter #1
Hi,
Im hoping someone can tell me where the A/C clutch relay is located on my 91 300se. All the repair cd's I have say its located behind the battery, next to the fuel pump relay. I have pulled the battery out and there is nothing back there. The problem Im experiencing is that the A/C clutch will not engage. I have checked freon, tested the inside temp sensor( resistance changes properly), changed out climate control with a used one, and if I apply 12VDC to lead on A/C compressor, it will engage, and I get cold air. Something is not working between the climate control and the A/C compressor. If you have any ideas on this, or know where the A/C control relay is, please let me know.
Thanks
 

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I believe 1990 and 1991 had a MAS sensor instead of the various relays, plus the OVP relay. Not sure if the Klima relay is integrated into the MAS or just the FPR. Its not on the pass side by the battery, but more towards the driver's side near the fuse box.
 

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1991 Mercedes Benz 300SE
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10 Posts
Discussion Starter #4
I inspected the fuses, visually. I can try to ohm them out, but I think if I recall that there are many other things run off of that fuse, and they work. Any body know anything about the high pressure switch mounted on the receiver? One switch makes the electric cooling fan come on and the other, I assume is the high pressure switch. I set the freon pressures by pressurizzing until the switch was open, and then removing freon until the switch was closed. This should give me adequate charge. Is there a low pressure switch anywhere in the system?
 

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CH4S Admin , Outstanding Contributor
1985 500SEC, 1991 190E 2.6.
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40,651 Posts
I inspected the fuses, visually. I can try to ohm them out, but I think if I recall that there are many other things run off of that fuse, and they work. Any body know anything about the high pressure switch mounted on the receiver? One switch makes the electric cooling fan come on and the other, I assume is the high pressure switch. I set the freon pressures by pressurizzing until the switch was open, and then removing freon until the switch was closed. This should give me adequate charge. Is there a low pressure switch anywhere in the system?
I only know about the pressure, and temp. switch, both with the dryer.
 
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