Coolant Temp Gauge Not Working

G'evening

Vehicle
1990 Ford Ranger 2WD 2.3L

Issue:
Coolant Temperature Gauge on the instrument cluster has stopped working. However will respond when sending unit wire is grounded(gauge then slowly climbs into red). Normally gauge will stay below cold but after some driving it'll go just above cold.

Possible Solutions? Normally I work on Volvo's and have found they are sometimes simpler/easier to work with.

Thanks Everyone

Sounds like bad sensor. Not sure where it is on your truck. Lots of folks here do, though. I'm sure someone will get you going.

I just replaced both the gauge and ECM sensors as they had both failed. The expected resistance at the temp sensor is about 250 ohms at normal engine temperature. Not having a OBDII data port you need an IR temperature gauge to clearly resolve the problem without parts swapping. You should have an 180*F thermostat and the IR reading should not get below that with an engine warm or above about 195*F on the high side.

Remember, you have thermostat, radiator blockage and water pump that can contribute in various degrees to the situation.

Long discussion on the subject here:

http://www.jaguarforums.com/forum/xk8-xkr-x100-17/normal-engine-coolant-temperature-138312/

Bobmbx said:

Sounds like bad sensor. Not sure where it is on your truck. Lots of folks here do, though. I'm sure someone will get you going.

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I replaced the sensor within the last year or so and then got stubborn and warrantied it. Both have given me the same result.

Coolant Temperature Switch on this vehicle is located driver's side right rear portion of the engine on the cylinder head. Real pain in the butt to get to.

TestPoint said:

Remember, you have thermostat, radiator blockage and water pump that can contribute in various degrees to the situation.

Click to expand...

Water Pump, thermostat, radiator cap, and upper/lower hoses are all good. Replaced thermostat and cap this year. Water Pump I checked when I pulled this truck outa the woods (was my grandmothers and now I use it as a work truck) and did a timing belt job on it about 6-7years ago.

Reason I know Water Pump is good? I've used an Automotive Stethoscope on it semi-reg (basically waiting for it to give me an issue).

Should be noted:
This truck has had this particular gauge problem for over 5 years now, i've just now gotten fed up with it. Engine runs fine otherwise possibly needing a valve adjustment and another timing belt job.

On a truck that old, have you given any thought to just putting in an old school direct reading gauge?

BobRob said:

On a truck that old, have you given any thought to just putting in an old school direct reading gauge?

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Not really, for two reasons:
1, the truck isn't truly mine (its my mothers, though I do use it as if its my own).
2, I believe I proved its an electrical issue and that the instrument cluster gauge does function as its supposed to.

Note
It has been suggested that I replace the "sending unit" Isn't that the wiring going from the actual temperature switch to the instrument cluster gauge?

I've done cumbersome work like this before and not opposed to doing it again btw.