Temperature Light on '02 C240

If it's a faulty thermostatic switch, you can buy an aftermarket switch and replace the faulty one.

Or rig a manual switch on the dash and turn the fan on when needed.

Or bypass the switch completely and let the fan run all the time.

There are not very many parts that are not available singly. A temp sensor for your car is around $20.00 USD (destination inside USA) from this guy (usual disclaimer).

I agree with lyn, the temp sensor is a likely candidate. Did the mechanic reveal any of the trouble codes to you? If yes, you can figure out what the car is reporting as trouble. With this information the 'Let's replace a bunch of parts and see if that works' rodeo is usually less painful.

It wasn't throwing any codes because it doesn't always do it, the only thing that happens is the temperature gauge will start showing up but the temperature never reaches 100C. The nuisance of it all is that the ac will blow warm air if you are sitting in traffic. Thank you for your suggestions.

If the ECM (control module) thinks the car is overheating, it will reduce engine load where it can. This will include shutting down the air con compressor. So if the temp sender is sending an incorrect overheat signal, the air con will blow warm air.

"...never reaches 100C." How do you know this? That is certainly not a coolant overheat temperature.

Because when the temperature light starts showing, the gauge is between 90 and 100, and the car does not run like a car that is overheating. No steam, no spitting and sputting, no missing, no cutting off, no nothing but the temperature light showing and the a/c blowing warm air

The part in 2 showing is the ambient temp sensor and has nothing whatsoever to do with the engine temp. The cooling fan on the Mercedes is a unit assy. that has a controller connected to the fan assy. and is sold as a unit. If the engine control computer is receiving a high temp signal then it will shut down the a/c compressor to remove the load from the engine and therefore allow the engine to cool down. The part number for the coolant sensor is 000-542-5118-OE Coolant Temperature Sensor and is only available from MB but can be bought online for under $20.00. Unless you have access to MB's BluTEC program then it becomes a trail and error and I would go for the $20 dollar part before I would replace the fan and controller for around $600.00 online price. Good Luck

Thank you, what you explained is exactly what my mechanic explained, however he said you couldn't buy them seperately, and since I don't know anything about repairing myself, I have to go with what he says.

The sending unit is able to be bought separately. Logan the fan assembly is all electric so does not have a fan clutch like your dodge pickup but will adjust the speed of the fan dependent upon the load that the ecm is detecting in the engine load. Mercedes has one of the most sophisticated systems that are used in the automobile industry.

There you go Jim. Good advice, and a Good Answer.

That is one of the nice things about CR4. Somebody will finally come by that really knows what to do.

Will our OP be able to get the part number you provide at the MB dealer?

I don't know that vehicle so I may be way off base here, but does the fan assembly include a clutch unit? Your visual inspection about the fan throttling back seems similar to what I saw on my old Dodge pickup. The replacement clutch assembly was $50 USD and it worked great after I replaced it. Hope this helps.

Logan