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Old 04-19-2002, 06:33 PM
GregS GregS is offline
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Join Date: Apr 2000
Posts: 459
Interchangeable fan temp switch & electric fan updating

I have see a lot of questions on this board from people asking under what circumstances and temperatures the electric fans on Mercedes turn on, and I have a question:

Does anyone know whether a lower temperature sensore could be swapped in? Seems like most switches are designed trip the fans at 110 degrees, which seems quite high and makes everyone nervous seeing their car reach that temperature. My Saab had a switch that turned on first at 90 and 88 degrees thereafter. Everyone on the Saab webpages knows to order a certain VW part number and you get a fan switch that is exactly the same size (so it fits in the Saab radiator), but turns on at all times at 82 degrees (which coincides with the thermostat). Saabs are notorious for overheating because of this odd arrangement with the factory fan temp switch, and a simple swap fixes the problem. Seems like the same problem we have with Mercedes, so does anyone know whether a lower temp switch from another car would fit in place of the factory switch?

Secondly, why didn't Mercedes design the fan to be on whenever the a/c is on? Seems like you need it on for best cooling with 134a. Again, on Saabs, you hit the a/c and both fans come on and stay on until you turn the a/c off - and I'm pretty sure most other modern cars are set up the same way. Mercedes are very well engineered cars, but with my plans to convert to 134a, I'm thinking it wouldn't be bad to update the cooling system to more modern standards!

Lastly, the time delay on the Saab outfit would be nice to continue cooling the car even after you have shut it down. Think about how hot the engine gets in the summer after you shut it down.

Any ideas? Has anyone outfitted a w123 with aftermarket electric fans? I'm thinking about swaping in an entire Saab outfit for optimum summer cooling and a/c efficiency. Would there be any drawback to this? The only thing I can think of is additional load and stress on the alternator.

'84 300D
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