Aux electric fan?
 

The aux. electric fan in the very front doesn't ever seem to go on. It's supposed to turn on when the AC is on, right? Because it doesn't.

Yep, it is. Start with the easy stuff - the fuse for example. You also can jump the switches on the receiver drier so that the fan will always be on high while the key is in the on position. Beyond that, I'll defer to one of the OM60x experts.

A slightly low refrigerant level will prevent the temp switch from actuating, as the refrigerant will not get hot enough to close the switch.

Not necessarily.

Fuse is fine and there should be enough refrigerant (just filled it). What's a receiver drier and what's the switch look like?

ETA: there's some type of outlet plug with a cap on it. Looks like I can connect it to an extension cord and plug it in. I really don't think I should, but what could it be for?

It should also go on when the engine coolant temp reaches 100*C. I find mine doesn't come on very often even with the A/C running on a hot day, but my cooling system is working excellent right now and I am a tad low on freon.

Auxiallary heater?

It's the block heater for easier cold weather starts. All the 124 diesels came with them from the factory, but the cord wasn't hooked up. Apparently there was a coupon to have it hooked up by the dealer. People in cold climates had it done. Where was you car from?

Chris

Ah I thought I read there should be a block heater on the W124 diesels but I just figured mine didn't come with one.

Not sure where mine was from, but I think I'm the 4th owner.
Does the cord mean I have it hooked up?

One is a pressure cut out...
 

The other is the temp switch. Each have two wires with spade/push on connectors. Temp. switch should be the slightly smaller of the two. The receiver is a black beer can size piece mounted through a hole in the inner fender, below the P/S pump, right behind the radiator. There is a line on top if it with a small (1 cm) glass window in it.ALSO the aux fan has a ballast resistor (porcelain) under the ABS unit just behind the D/S headlight. Sometimes they can crack and corrode...have a look and let us know.

Yes it does, but I doubt you will need it in San Diego.

Chris

That depends on which switch you have in the car. Scroll down to #7

http://www.peachparts.com/shopforum/diesel-discussion/165095-w124-fuse-question.html

I use a switch from the 201, 006 545 42 24 it is a 100/110 so the aux fan comes on at 100 and the A/C shuts off at 110. I replaced mine last year and it already died. If you have the original switch in your car it is probably not working.

Chris

So what does this mean?

http://www.mustangmods.com/ims/u/408/5282/184628.jpg

So I attempted to short the switch on top of the receiver drier, nothing happened. Is there something else I can short to see if it'll turn on?

The top one is the pressure switch for the compressor. The switch with the pig tails is the freon temp switch.