Coolant temperature sensor

RICK PIPER

MEMBER
2003 FORD E-SERIES VAN
4.2L
V6
2WD
AUTOMATIC
230,000 MILES

Long story short. My temperature gauge does not read my last test was to take the sensor out put the connector on and use a heat gun to heat the sensor every thing worked as it should. Put sensor back in did not work again, my assumptions where either the water was not up to the sensor or a bad connection. I backed the sensor out several times to make sure no air was trapped, no change next I moved the connector back and forth up and down left and right still no gauge movement. I am all out of ideas. Somebody help!

5 Replies

STEVE W.

MECHANIC
13,462 POSTS

My first thought would be a new sensor. It is very possible that it has a bad internal connection and heating it helped enough to make it work during the test, then engine vibration makes the connection fail when installed. It could also be a bad wire in the harness to the sensor and moving it around made it connect for a bit.

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Thursday, November 30th, 2017 AT 7:26 PM

RICK PIPER

MEMBER
3 POSTS

This is the third sensor. The wiring is still possible. Does the length of the sensor matter?

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Friday, December 1st, 2017 AT 5:09 AM

STEVE W.

MECHANIC
13,462 POSTS

Okay, did not see that you changed it. In that case it has to be in the harness. Start with a tug test, basically pull on the wires where they enter the connector, they can corrode right inside and fail. If they stay together then you will need to work your way up the harness looking for either a broken wire or bad connector. As you had it working a bit I think the issue will be close to the sensor.

Sensor length is not a problem as long as it threads in and does not bottom out. Just be sure it is the correct part number.

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Friday, December 1st, 2017 AT 5:17 AM

RICK PIPER

MEMBER
3 POSTS

Thanks for your help how many volts should I have at the coolant sensor

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Sunday, December 3rd, 2017 AT 7:04 PM

STEVE W.

MECHANIC
13,462 POSTS

Well if the wiring diagrams are correct, one side should be at the reference voltage (either 5 or 12 volts) and the other side should end up at ground back in the PCM.

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