My wife has a 2002 SLK230 with 32K miles on it. For the last several years she has experienced the lighting of the temp/coolant idiot light (the thing that looks like a little radiator). There are no leaks, coolant is full, everything just perfect and it does not stay on long.

The dealership is clueless. They have "fixed" the problem under warranty previously but it just keeps coming back.

Last week they suggested a $500 alternator replacement, when the existing one reads 14V and was never pulled from the car and tested under load. It is not the alternator.

I'm stumped because the coolant levels are perfect- filled with the correct mix of coolant/distilled water.

My wife is excellent because I have told her to never drive with the coolant light on and she follows this axiom. This leaves her stranded frequently and she does not trust the car over distance. Any ideas here?

I'm done with the dealership, unless someone here can tell me how a new alternator can turn the coolant/temp light off...

 

Hi,
Probably wants a level sensor on the coolant resevoir. Have a look at the wiring, see if its not frayed or cut etc. If it's not the wiring then definately the sensor i'd say!