I'm just about ready to donate this thing to Charity.

1992 300E: No fans coming on at all. Resistor glowing BRIGHT red when car gets at all warm (bright enough to shine on the garage wall).
Recently replaced:

One electric fan.
Resistor.
Updated relay for high speed fans.
Temp sensor mounted on head.
Head Gasket.
New, clean fuses.

The dealer says something is grounding out. The wiring to the fans looks fine. The wiring coming off the resistor has the insulation burned, but nothing is touching metal. I tried putting a new fuse in the high speed relay, but it blows when I turn on the key.

Could it be:
A: the other fan out (would it keep the other from working).
B: The low speed relay burned up.
C: The wiring to the fans has somehow been cut.

I'm at my wit's end with this car. Just got it out of the shop from replacing the fuel hose. Seems like something daily. I miss my diesel now...

I'm going to get a new low speed relay this weekend at the dealership. I would value ANY thoughts on this before I call a tow truck... :(

THANKS!!!

Hello:

I had a similar problem as you. I changed the wire coming off of the resistor and it fixed the problem.

As explained to my by my mechanic, once the wire heats up like that to melt the insulation, it creates higher resistance in the wire itself.

Hope this helps.

Aloha,
Eric

Thanks Eric!

Which is the one coming OFF the resistor...the one on the left or the one on the right? I hope I don't have them reversed, although I wouldn't think it would matter. I also think the wire might be cooked.

Does that wire go directly to the fans or back to the relays? Also, what is that wire called when I go to the dealership?

Thanks for your help. It may have to be towed to the mechanic, or I guess I could unhook the wire and drive it a short distance with the A/C off.

Thanks again!

You're building the house from the roof down
 

Brother of the Benz, TCCBass
You're replacing components without identifying the bad fellow.
Have you tried disconnecting things in effort to find which unit is the bad one?
Try disconnecting components down stream of the Pre-resistor to eleminate the large load.
It's amazing a fuse doesn't open.
Continue disconnecting until you have removed the load.
With everything disconnected, and the load is still present, use your volt/ohm meter, on resistance x-1 scale and test the wiring to ground. Be certain the supply wire for the P/R is disconnected.
Nothing up stream from the P/R will cause this condition.
It is easy if you do it in the right sequence.
Happy Trails Beep Beep from The Spiderman in Houston!!!

I plan to start Monday unplugging things until I get some kind of result. When you say downstream...

Fans?
Relays?

I would perhaps suspect that the older fan is perhaps out, but was working just fine the first of last week. I had a coolant leak, and it ran short of water (VERY briefly...I added before it really got hot). I don't have an ohm meter, but I guess with this car I should invest in one.

Thanks for all your help!