Engine Temperature Sensor

Does your water-temperature meter show only low temperature ? Even if you were driving for hours ? And your heating works well ?

Well - then maybe your engine-temperature sensor is broken.

I had this once and I was wondering why the meter in the dashboard reads only low temperature and my car uses some more fuel than usual. This comes because the sensor also generates a signal for the fuel-injection system weather the engine is cold or hot. If the sensor always generates an 'engine cold'-signal the fuel injection will add some more fuel as required on a cold start condition - even if the engine is yet burning hot. This additional fuel is a total waste. There is an additional danger too: you can't see when you engine is overheating. So I checked the wiring and the meter and everything there was okay, so the sensor must be defective. After replacement meter reading and the fuel consumption returned to normal values.

Locating the sensor: Open the hood and look over to the left side from your point of view. You will see the generator belt and the engine mount. Just behind the engine mount is an aluminium domed housing which contains the thermostate from the cooling system. The sensor is screwed just vertically in there. It has a hexagonal housing (about 12 mm), is made of brass and a black round connector is fitted to it. The wiring colour is purple with a thin yellow line.

Look Here to see a picture that may help.

Testing meter and wire: You will need a piece of thin metal (cable or wire) and a second person, which must not be a technician. Remove the connector from the sensor by pulling it gently upwards. Switch the ignition on but don't start the engine ! (for security: the running generator belt may cause severe injuries, if your fingers, clothes or hair get caught by it). The second person will watch the meter needle while you make a contact from the metal inside of the connector to the metal body ground (i.e. the engine block or the intake manifold). Apply the connection only for a few seconds, it will be enough to let the meter needle reach the right-most position ("hot like hell"). Your second person should tell you if the needle reaches the end of the scale.

Result of the action: If the meter reaches the end of the scale, wiring and instrument are in good order and the mistake must be within the sensor. Connect the sensor cable again, close the hood and drive to your workshop to have the sensor replaced. If you are not concerned about warranties or believe to be a somehow good mechanic, you may consider doing the replacement by yourself (what I did ...).
In fact it is a five-minutes job - after the engine has cooled down !
The only problem is not to damage the new sensor or to overtighten it. In this case you only need to order a new sensor from Chrysler. The Part-Number of the Sensor is P/N 4504-203.

Reports: None at this time


Last Update 30. January 1997
© 1997 by Peter H. Wendt