Hi,
I have a UK 1993 Mercedes 190E 2.0 Auto. For the past few weeks my temp gauge has been wildly fluctuating. Up to about the 100C mark and it seems to behave itself. However, the needle has started to twitch/fluctuate and then it soars to 120C and once went off the scale(!).
If I tap the cluster the needle will often go back down to about 90C (where it should be). If I turn the car off and on again it has the same effect: drops to about 90C.
The car doesn't appear to be overheating and is no loosing any coolant. It drives well and the head gasket was done 7 years ago. There is no mayo in the coolant bottle. However, understandably I have a niggling worry in the back of my mind that I might be frying the engine...
I have bridged the connector for the fan sensor with a paperclip and the fan does come on.
The fan temp sensor has three prongs (sensor to the left) it is not the one with four prongs that provides a temp reading to the ECU (big round one on the right). Two of the three prongs are to activate the fan and the third is a single prong which drives the temperature gauge. I would like to test the reading given out by the third prong. If it says something reasonable like 90C but the gauge is reading 100+ then I know the fault is likely to be the wiring to the gauge or the gauge itself. Problem is I don't know what to measure at that third pole (resistance)? Does anyone have a resistance/temperature chart for this sensor so I can compare the sensor output to the gauge?
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I have a UK 1993 Mercedes 190E 2.0 Auto. For the past few weeks my temp gauge has been wildly fluctuating. Up to about the 100C mark and it seems to behave itself. However, the needle has started to twitch/fluctuate and then it soars to 120C and once went off the scale(!).
If I tap the cluster the needle will often go back down to about 90C (where it should be). If I turn the car off and on again it has the same effect: drops to about 90C.
The car doesn't appear to be overheating and is no loosing any coolant. It drives well and the head gasket was done 7 years ago. There is no mayo in the coolant bottle. However, understandably I have a niggling worry in the back of my mind that I might be frying the engine...
I have bridged the connector for the fan sensor with a paperclip and the fan does come on.
The fan temp sensor has three prongs (sensor to the left) it is not the one with four prongs that provides a temp reading to the ECU (big round one on the right). Two of the three prongs are to activate the fan and the third is a single prong which drives the temperature gauge. I would like to test the reading given out by the third prong. If it says something reasonable like 90C but the gauge is reading 100+ then I know the fault is likely to be the wiring to the gauge or the gauge itself. Problem is I don't know what to measure at that third pole (resistance)? Does anyone have a resistance/temperature chart for this sensor so I can compare the sensor output to the gauge?
