Tempreture Sensor

Discussion in 'Electronics' started by rod smith, Sep 14, 2011.

  1. rod smith

    rod smith New Member

    Jun 3, 2011
    1996 c180 classic
    Can anybody tell me where i would find the temp sensor for the cooling fan on my 1996 c 180 and how i can test if its faulty Thanks in advance
  2. millo777

    millo777 MB Enthusiast

    Mar 9, 2011
    Swansea, Dubai, Riyadh
    1997 W140 S600L/2003 S211 320cdi
    I have no experience of the w202 specifically, but if you're talking about the electric fans for the AC, they are switched from a sensor on top of the thermostat and from a feed on the ac pressure switch. For the ac fans to work the car has to be above 90c and the ac switch on. In the uk you'll rarely see these kick in.

    If you're talking about the main cooling fan, it could be either electric, in which case it will be switched by a temp sensor which is likley to be on the thermostat housing. To test if it's the switch thats faulty, disconnect the 2 wires from the sesnor and short them out which should start the fan. If the fan starts, then obviously it's the switch thats faulty.

    The main fan could also be a viscous clutch, which is switched in and out using a bi-metallic strip on the front of the clutch. The proper way to test that type is get the car up to about 100c (just rev while parked) and see if it kicks in, which should be easily audible, and bring the car back down to normal operating temp pretty quick.

    If it's a viscous clutch type, another indicator isseeing how much run on the fan has when you turn the engine off. A new clutch will stop the fan dead immediatley when the engine is stopped, an older one that isn't doing too well will carry on spinning after the engine is stopped. There is also the "carrot test" for viscous clutches. With the car up to about 100c gently insert a carrot into the blades. If the fan shreds the carrot it's o.k. If the carrot can stop the fan turning it's dead. I've just been through all of the above with my w124, and really the noise test is best option.

    Hope that helps.

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