My temperature gauge stays on cold it never moves but car is not over
Why does it the temp Gage move ..it stays on cold
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Hi,
Here is an image showing the location of the two temperature sending units (or sensors) for your vehicle.
The one on the left, where the single wire black connector has been disconnected is the sending unit for the dashboard gauge.
The one on the right with the grey connector (and being held by fingers) is the ECU temperature sensor.
(click on image to enlarge for better viewing)
To test the sending unit, disconnect the single wire black connector and using a DMM (Digital Multimeter - Ohmmeter function) measure the resistance between the sending unit terminal and earth (or ground - the engine block will be earthed). With a cold engine the resistance should be approx 140 Ohms. With a hot engine it should measure 30-50 Ohms.
If it reads approx. 140 Ohm (or more) when the engine is both cold and hot then the sensor is faulty and needs to be replaced.
If the sensor reads 30-50 Ohms when the engine is hot then there may be a problem with the wiring back to the gauge or with the gauge itself.
Be safety aware
Make sure the engine is turned OFF and that the vehicle's ignition key is in your pocket when you test the sensor. Also don't burn yourself on the engine block when the engine is hot
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Did you say that it should read 30-50 Ohms when the engine is hot? Then you said, if the sensor reads 30-50 when the engine is hot then there may be a problem with the wiring… I am confused. Are you talking about two different things?
Hi,
What I meant was disconnect the sensor lead and measure the sensor while it is still in the engine block.
If it is reading 30-50 Ohm when the engine is hot (be safety aware turn off motor) then it is OK but if the meter is still registering full scale then there is a problem further back towards the meter.
jayeff your still not making sense, 30-50 ohms is normal w/ hot engine, what do you mean by registering full scale, zero = short, infinity = open circuit, which direction?
Hi @amida
I can't alter my comment now because it was made too long ago to edit, but the meter I was referring to was the car's temperature gauge.
If you disconnect the lead from the coolant temp sensor in the engine and then use an Ohmmeter to measure the resistance between the sensor's connection point and earth on a hot engine it should read 30-50 Ohms. On a cold engine it will read ~140 Ohms.
If not either of these readings then the sensor may be faulty
If you have measured the coolant temp sensor in isolation (i.e. lead disconnected) and it measures 30-50 Ohms when the engine is hot or 140 Ohms when cold and the car's temp gauge still doesn't register with the sensor lead reconnected then there is a problem back towards the gauge and not in the sensor. It could be the wiring, the harness connections, instrument panel pcb or the meter itself
If you disconnect the lead from the sensor and the car's temp gauge still registers hot (or full scale deflection) with either a hot or cold engine, then there is a problem back towards the gauge and it is not the sensor.
Full scale deflection means that the gauge needle (or pointer) moves as far from zero as possible i.e. maximum movement across the scale
Thank you Jayeff for taking time to explain this. Even though I have a 2000 Excursion with no temp reading and an OX2 and HTR not fulfilled error code I still benefited from the values and explanation of the principles. If I used a 50 ohm resister to simulate my sensor value and my gauge read normal range I could assume that my wiring is good and I am in fact looking at a bad sensor.
