On an '83 300D, the auxillary fan runs continuously. No doubt it is better to be on at all times rather than not come on when it's supposed to. Anyways, if someone can point out the temp sending unit or whatever triggers this fan to turn on, I would greatly appreciate it.

The aux. fan should come on with either the temp. sending unit (105C) or the pressure switch on the drier/accumulator for the a/c.

I am unsure of the location for the temp. sending unit for this but I believe it is near the thermostat housing. Maybe someone will chime in and pinpoint this or, if you are on better-than-dialup, try here: http://mb.braingears.com

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Sam

84 300SD 350K+ miles ( Blue Belle )

Is it staying on when car is turned off ? Or just when its running ? It may be a stuck relay,or something that controls the relay.Johnny

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85 300sd SOLD ,85 745i,95 740i,1972 Suburban,1938 International

First place I'd look is the switch on the very top of the dryer. Unplug one lead to this switch. If the fan shuts down, you've found your culprit.

Otherwise, you'll have to find the switch on the head that controls the fan...........and do the same thing.

The fan runs when the car is running.


Thanks folks. As always, your help is appreciated.

I don't know if you just bought this car, but I just bought mine with the same problem. I went to change out the temp sender and found that the 2 terminals were jumped with a piece of wire. Took the jumper wire out, put the new temp sender in, and then the fan wouldn't work at all. So I put the jumper wire back in, and have learned to live with it. It's probably better for the cooling system anyway with this
summer heat.

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87 300D - Running on Veggie oil; 260,000 plus miles; Original #14 head