Two Coolant Temp Sensors.....Which is Which?

[Runnin'OnEmpty]

I have two coolant temp sensors on my 00 4.0 OHV. One (gray) is near the thermostat housing, and the other (white) is to the rear and left of the first. I know one is for the gauge and the other (ECT) is for the PCM input. I am confused as to which sensor controls what?

The rear one (white) has a two wire connector with red and white wires. The front one (gray) has only one red/white stripe wire going to it, BUT it has a two wire connector, and two connectors on the sensor itself????

I've noticed lately that the temp gauge barely registers, and thought I'd check out the sender unit before changing thermostats. Is the gauge sender the front one?
Thanks.
Don

 

[Sonny]

My Haynes says. the ECT should be a gray plastic body and the IAT should be tan or brown. Maybe yours have been changed before. I think I would unplug one of the sensors and see if my temp gauge did not rise at all, if so that would be the correct sensor... I just thought of something, you can check your thermostat; when engine cold!!! take off radiator cap, if needed drain out some antifreeze just to below the neck. Then start it up, and look at the remaining antifreeze, if its flowing I think your Tstat is stuck open and causing the low reading on the gauge, the Tstat should take a few minutes to open, then the water would start moving. Maybe someone else will help out if I missed something.

 

[ipozestu]

You got it buddy. The gauge sender is the front one.

 

[BillWms01]

I recently changed this sensor on my '97.

The two sensors have different electrical plugs. At NAPA, one of the guys knew his fords, and said that the gauge one is listed as a "switche", but the PCM one is listed as a "sensor". So, if you're working a gauge problem, ask for the temp switch.

Needless to say, I had gotten the "sensor" (at Autozone), and it wouldn't plug in. When I returned it, they couldn't find another "sensor" listed.

I went to NAPA, and the first counter guy couldn't find the right one either. That's when the other guy overheard the problem and came to the rescue.

Since you're gonna loose coolant down to the thermostat anyway changing the sensor, I'd go ahead and change it. That's probably the problem.

 

[Runnin'OnEmpty]

Thanks for the replies, guys. You're all correct, the temp gauge sender is the one nearest to the thermostat housing. What was throwing me off was the two wire plug, although only one wire is connected to it.

I'll probably take BillWms01's advice and replace both the sender and thermostat, since winter's coming on.
Thanks again.
Don