My aux fan wont shut off after the car is off, and I hear a clicking from under the hood as the fan turns off, on, then back off ect..... I think the fan relay is stuck or broken. Can anyone tell me where this is located? 1990 300E 3.0

My bad. The fan runs on high speed, only when the car is running. When I shut off the ignition, the fan turns off. The only time the fan is not running, is when I start it first thing in the morning, and the car is cold.

behind the fuse box..a few phillips screws hold the cover..

Ok thanks I got the cover off. There is a green one in front, then a silver, then a black, then two whites side by side. These are the square ones. There a two longer looking rectangular black ones. Do you know which one it is?

Sounds to me like you have a bad connecvtion at the temp sensor or a failing sensor..the relay would not click if it was stuck in the ON pospsiton

Yoy can tell which relay by unplugging it when the fan is on. Sould be the green one

I unplugged the black one, and the fan shuts off. I heard it clicking on and off, and the fan was turning on and off real fast. I guess I could try and replace the relay and see if it cures the problem. Where is the temp sensor located?

Swap that one woth the green one ..they are the same....

ok if my car blows up, its your fault. hang on

They arent the same. The green has 5 prongs, the black 4. Wont fit

By the way, my A/C is in the off posistion, and I know for a fact I have no refrigerant in the system. Would this temp sensor switch on the dryer still send a false signal to the fan relay? With the fan relay in, the fan runs on HIGH.

a/c sensor is not a temp sensor , it is a high side pressure sensor ..and a/c fan is LOW fan..nothing to do with High fan circuit...

High fan relay for chassis 124.030/1990 300E is position slot "C".
Low fan relay is slot "B"
These are both 4 prong relays , according to my schematics.. and should be interchangeable..

Then what is the high fan for? I was told the auxillary fan has nothing to do with coolant temp. It was only for the A/C? Slot b and c???? Im just telling you what I see. three prong and four prong. I will look again

Slot b is a 5 prong. c is a 4 prong, and d is a 5 prong.

Oh, I see..
I thought high aux fan was coolant temp triggered at 105C , using the blue 2 terminal thermistor at the thermo housing, with the circuits load going through the high fan relay in slot C.

And the a/c low aux fan was triggered with the high side pressure sensor at the a/c reciever/drier...low fan being accomplished through the pre-resistor [dropping resistor] , using the relay in slot B.
If they are not the same # of terminal, the schematic does not show that.
I think the extra terminal is just a plastic orientation tab on that relay.

If you were told high aux fan has nothing to do with engine coolant temp, then one of us is incorrect..........
You may just want to do an Aux Fan search and see..

I did a search for this and read the aux fan is only for the A C. Someone said the clutch fan is sufficient for engine cooling and there was no need for an Aux fan, this was only for AC condensor. Im just telling what I read. Please I am not trying to sound like a smart ass. I know nothing of these things. Just trying to stop my fan from running all the time. I removed the relay, and since I dont use my AC, I will just leave it out.