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Old 06-15-2003, 10:16 PM
GregS GregS is offline
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Join Date: Apr 2000
Posts: 459
Arthur Dalton - here are some more pieces to my puzzle...

First of all, I want to thank you for all the help on my last thread about the aux. fans on my '90 300CE. See: basics checked, but w124 fans still not working

Problem is, things still aren't quite right. After a lot of testing, cleaning contacts, etc., I discovered:

1) that my relays and fuses are fine,

2) that the plug where the aux. fan harness from the fusebox and the harness from the fans plug together (right next to the receiver-drier) has either a bad connection or a bad wire (this was the real problem), and

3) something is stilly fishy with the drop resistor and coolant temperature sensor.

Here's the issue: when I bypass the drop resistor, BOTH fans will work when I jump the a/c pressure switch. They both work whether the coolant temp switch is connected or not. This seems strange. If I re-connect the drop resistor only the a/c fan (passenger side) works. If I re-connect the drop resistor, the driver's side fan does not work, but the passenger side will work as designed - when the a/c switch is hooked up and the a/c is on.

Bottom line is, I think my drop resistor is bad because the driver's side fan doesn't run when the reistor is hooked up, but I'm still baffled as to why the coolant temp switch didn't seem to have any affect on things?

My other question is whether the a/c switch works on varying pressures. Is it possible that there is enough pressure to engage the a/c fan but not the coolant temperature fan?


'84 300D, 174k
'90 300CE, 164k
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