question about 190E Aux Fan pre-resistor - PeachParts Mercedes-Benz Forum

milltek · #1 09-01-2004, 05:44 PM

Hi,
The car is a 1989 190E 2.6 from California.

Here's the question;

All my freon was gone due (it turned out) to a defective, leaking schrader valve.

When the A/C shop was filling it they pointed out that my aux fans should run when the air is on. So he referred me to another independent MB specialist. Off I went and he said that my pre-resistor was shot. As a temp measure he pulled the plug of the coolant temp sensor under the edge of the air-filter box, which makes the fans run on high all the time. I drove it home and got a pre-resistor this morning.

The pre-resistor lives down beside the receiver-drier on my car and is a ceramic-type thing about 4 inches long and one inch swuare on the ends. There are two connectors with one wire apiece.

When I put the new one in place and ran the engine, everything works as advertised. The fans come on low with the air and hum away nicely.

After a few minutes I noticed a strange smell which I traced to the new pre-resistor. The I touched the thing and just about screamed. It was red-hot to the touch. Is this usual? If not, what could be causing it to heat up like this????

I'd appreciate any answers asap as I am afraid to run the car with this issue. I don't want a fire!!

Thanks

Jim

mbdoc · #2 09-01-2004, 05:51 PM

That is what a resistor does! Used up some of the battery voltage to lower the voltage going to the consumer. YES very hot.

milltek · #3 09-01-2004, 06:14 PM

OK. Just doesn't seem very MB-like. The resistor has both it's terminal coming out through some past-like stuff that was grey/opaque but this has alreay turned brown. Is this expected? I compared the physical turning resistance of both fans to the two on my 99 ML430 and all seem to be about the same.

I really like this 190 and don't want to damage it.

Jim

mctwin2kman · #4 09-02-2004, 08:27 AM

Resistors get hot! They cut down the amount of power going to the intended item, in this case the fan! Well to cut down the power something has to get hot to dissapate it! That is the resistor in this case! Perfectly normal in this case!