Can anyone explain what he means by negative and how do I do the test...

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James A. Harris

Maybe it's right, it could be the thermostat. I always thought changing them should be part of regular maintance. If you've never changed it now would be a good time.

And the replacement thermostat cover is now metal.

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5 speed '91 190E 2.6 320,000 mi. (new car, fast, smooth as silk six, couldn't find any more Peugeots)
5 speed '85 Peugeot 505 2.5l Turbo Diesel 266,000 mi. (old car, fast for a diesel, had 2 others)
5 speed '01 Jetta V6 (new wifes car, pretty quick)
5 speed '85 Peugeot 505 2.2l Turbo Gas 197,000 mi. (wifes car, faster, sadly gone just short of 200k )
5 speed '83 Yamaha 750 Maxim 14,000 mi. (fastest)
0 speed 4' x 8' 1800 lb Harbor Freight utility trailer (only as fast as what's pulling it)

Thanks Jim, I just got the car actually. I'm not sure if the previous owner changed it but the thermostat cover is metal. I was wondering about that because in the Haynes manual that also came with the car it shows a picture of a plastic cover.

I'll try shorting the connector to the temp gauge and see if it'll spike to overheat

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2008 BMW 335i Coupe

I will buy some resistors to test the gauge this evening. But I took some readings and it came back as 800ohms and the gauge read 40*, maybe a hair above it.

It did fluctuate wildly between 400-800 though.

I sprayed some electric parts cleaner on the sensor and its surrounding area (including the harness connector) and now the gauge jumps around more but does read above 60*

will try to clean the contact points of the sensor and see how that goes.

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2008 BMW 335i Coupe

UPDATE: I cleaned and sanded down the connecting surfaces of the harness and sensor. The gauge is now consistent and not dancing around.

I grounded the harness to the ground and the temp gauge shot to 120+

So the gauge works, the temp sender is fine.

The temperature was still at 65-70 on the highway and between 75-80 when I'm idling in a warmer place (a garage).

I guess it's the Thermostat - I wonder if it even has one

Thx for all the help guys

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2008 BMW 335i Coupe

Look at the chart....negative means as the temperature goes UP , the resistance value [ Ohms] of the sensor goes DOWN [ negative].

So , you measure the ohms and compare it to the gauge ..
I have a 38 ohm resistor in my tool box for checking these real easy..if you sub that resistor for the sensor, the gauge has to read 100C... just like the chart I posted says............simple.

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A Dalton