Auxilliary Fan does not kick in
 

The auxilliary fan on a 1996 S420 does not kick in.
At idle the engine temp rises to 120 degrees but when running the temp is 80 degrees.

I tested the following.

1. I checked the fan separately and it functions in both directions.

2. I replaced temp. sensor top of the engine manifold.

3 Before replacing the temp. sensor I hooked up the car to a SNAP-ON diagnostic tool and it read negative 47 degrees. I did not check the reading after that.

4. I replaced the RELAYs just to be sure.

Is there anything that I am missing?

Thanks.

Neither fan works? No Low speed, no high speed?

Do a search, or just go through the pages in this tech help section...it was just discussed a day or two ago. :)

fuse?

Thanks for the replies.

The fan does not run at any speed. The fuse is good.

Does anyone know anything about the ESG Control Unit? I heard that this ESG Control Unit controls the auxilliary fan.

I am not sure what its function is. Any ideas?

I may be wrong but I think they run off a temp switch!:confused:


Smokie

Is there a dropping resistor for the fans in that car? In my 500E its behind the drivers headlite and over the years had gotten crusty.

You might have the newer style set-up, where there is no resistor behind the headlight, but some other (not-too-good) gadget between the fans. I should've paid more attention to the posts about that gadget, because then I could tell you its proper name. Either way, I believe the advice given, was to rip it out, and replace it with the spring type resistor (older technology, but it works better/longer).

Thanks to all who chipped in.

I had to clean the connectors of my Aux Fan control unit and it now works fine.

Since I replaced the relay, temp. sending unit, fuse, etc., I guess everything contributed to the system working and back to normal.

congrats man.