I hope someone can help me with this problem on my '90 300CE with a 104 engine. Based on a few recent posts, I have done the following in an attempt to diagnose my electric fan problem:

1) jumped wires that connect to the temperature switch on top of the thermostat housing - fans didn't work

2) used multimeter to test for power at these same wires - no power

3) used mulitmeter to test for continuity between resistor posts - I had continuity (just to make sure I'm testing the right component, this thing is bolted to the frame right beside the a/c receiver/drier, right?)

4) checked fuse - looks fine, and the other components on that circuit work fine

5) cleaned ground for fan harness

6) jumped wires that connect to the switch at the receiver/drier - fans didn't work

7) tested for power at these wires - no power


O.K., so what am I missing? I looked for relays, but couldn't find any in the engine compartment. I read that there are two relays, one for the a/c switch and one for the coolant temperature switch, but I couldn't find either. Where should I look?

Secondly, why isn't there any power at any of these switches when the engine is running? Would this be caused by bad relays?

Third, the a/c IS low. I know people say this could prevent the fans from coming on, but even if it is low, shouldn't the fans run when I jump the switch at the r/d?

Lastly, are there any other components tied into the fan wiring circuit that would cause me problems (like a bad coolant level sensor or something strange like that)?

I don't know what to check next!

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