My '90 300TE auxillary cooling fans are not running. My temps are getting above 110 when not moving and running around 100 when driving with the A/C on. What could be the issues here and how hard is it to check out. Any help would be appreciated.

Thanks,
Cal

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kaldonia:
1990 300TE 4Matic

Go check fuse #7,#D and check auxiliary fan
relay K10 low speed,K9 high speed,locate inside fuse box under hood ,also check
auxiliary fan preresistor locate behind driver side headlmp unit,coolant temp sensor
locate on top of cylinder head,auxiliary fan
switch is locate on deire (red) and possible
bad auxiliary fan motor(try to turn by hand)
hope this help.

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MB STARS Master Guild Technician,12 years MB tech
5 years independent shop owner

Fuses look good. What resistance should I get on the preresistor and - Where are the relays located and You say that the fan switch(which I suspect) is on the deire, where is that? Also both of the aux fans spin freely(seem OK). Thanks

Cal

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kaldonia:
1990 300TE 4Matic

The relay is locate inside your fuse box under hood you may have unscrew the cover to find the relays....auxiliary fan switch is on your drier (color red or green with two wires).....preresistor has two wires connect to each side check it if only side has power
other side not replace it resistance should
be 0 if is open replace it.

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MB STARS Master Guild Technician,12 years MB tech
5 years independent shop owner

I checked the preresistor and have about .01 ohms. I've jumpered out the Aux fan switch leads and the fans still haven't come on. The relays would both have to be bad. The main cooling fan on the engine side of the radiator in running because it is part of the belt assm. Is there any other way to get those fans running? Thanks

Cal

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kaldonia:
1990 300TE 4Matic

You need to look at the wiring diagram to see how it is wired so you can properly diagnose it.

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Benzmac:
ASE CERTIFIED MASTER AUTO TECHNICIAN
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