Electrical and A/C Problem - AC Auto Repair Help Forum


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Electrical and A/C Problem

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1littlecastle
New User

Jul 4, 2009, 10:08 AM

Post #1 of 3 (1401 views)

Electrical and A/C Problem	Sign In

I have a 1995 M-B SL320. The two A/C activated cooling fans in front of the radiator do not operate when the A/C is activated. The fuses and relays are fine. What's the problem and how do I fix it?

Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Jul 4, 2009, 12:07 PM

Post #2 of 3 (1395 views)

Re: Electrical and A/C Problem	Sign In

Engine off and keys out - will the fans even spin by hand - use a stick just in case?

They may have burned out and how do you know relay is fine? There should also be a trigger either of a few - A/C requested, high side pressure above a certain # or a ground that's weak or missing??

T

1littlecastle
New User

Jul 5, 2009, 5:41 AM

Post #3 of 3 (1381 views)

Re: Electrical and A/C Problem	Sign In

Thanks for the reply.

Yes, the relays are fine because I tested their electric conductivity. Yes, the fans turn freely by hand and make no unusual noises. I'm pretty sure they are not burned out because they used to work fine, besides, it would be unusual for both to burn out together. No, I haven't tried jumping the fan motors because they have to be removed from the support frame in order to access the electric connectors. I don't think the problem is within the fans because they used to work fine. I think the problem is in a thermo sensor that, like a thermostat, measures the ambient air and or engine coolant temperature before sending an on/off signal someplace. Because it's a M-B of 1995 vintage, and a model that M-B loaded with every concevable electric and hydralic gadget, it problably requires a descrete wiring diagram to be able to diagnose the problem. Do you have operation and wiring diagrams?

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