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Old 09-07-1999, 09:51 PM
Amin Lalani
Posts: n/a
I keep hearing that the auxillary fan should come on once the AC is turned on. I was looking around the car and decided to see if this was the case. When I turned the car on the temp gauge showed 100. I turned the AC on but the Aux fan did not start. I took a quick peak at the wiring and it all seems to be in place. What else could be wrong.

Old 09-08-1999, 12:14 AM
CMuc's Avatar
Join Date: Jul 1999
Location: Port Coquitlam BC, Can
Posts: 92
The fan comes on when the high side of the a/c system reaches a set pressure of about 250psi( benzmac knows the exact spec). You need special tools to test this pressure. The fan also comes on when the coolant is close to boiling. If your car isn't over heating and the a/c is working, I wouldn't worry about the fan as the other fan is handling the load.

Chris Muc
Auto mechanic
'87 300E 325,000 km

[This message has been edited by CMuc (edited 09-08-1999).]
Old 09-08-1999, 01:18 PM
Registered User
Join Date: Aug 1999
Location: Florida / N.H.
Posts: 8,804

Jumping the switch on top of the reciever
will energize the fan. I have a switch in parallel under the dash that comes in handy
anytime it's needed. [ hot, humid , in traffic days].
Old 09-08-1999, 09:50 PM
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Join Date: Mar 1999
Location: Suwanee, GA, USA
Posts: 4,712
Good point. The switch is the red or green switch that has two wires coming from it. Just bridge them together with the key on and the aux fan should run. If so you just tested it and it is fine. If not the fuse in the box (c or d) is likely blown. If the fuse is OK it may be the pre resistor.


Old 09-08-1999, 10:16 PM
Amin Lalani
Posts: n/a
I was wondering what is a good temperature for the car. No matter what happens my gauge always shows 100.

I have not done a lot of winter driving but since spring I have noticed it is always at 100 (Once the car has been running for a bit).

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