Coolent gauge operation

[johnanc]

Dr. Lee, Someone from the 6.2 site let me know which sendor was the correct one but am wondering how the sendor and coolent gauge system works so I can troubleshoot it. (Can the sendor be troubleshot while still installed?)

[CleviteKid]

Point number one: the temperature coolant gauges on our 1982-1987 trucks are notoriously inaccurate, so don't look for spot-on information. Look for trends or changes, and change your thermostate every year or two to keep the temperature where it should be.

Point number two: I think the sender acts like a variable resistor with temperature, but I do not know the parameters. Also, you cannot easily open it up and adjust it. I trouble-shoot it by replacing it with a new one and observing if anything changes.

Point number three: you got me thinking - my gauge always reads 150F, no matter what, so perhaps I should play around with adding offset resistors in the line to see if that changes anything. Hmmmmmmmmmmmmmmmmmm.

Dr. Lee :cool:

[arveetek]

You can check the guage with it still in the dash by turning on the ignition and grounding the wire that goes to the temperature sending unit in the head. When you ground that wire, the needle on the guage should move all the way to "hot." If it moves, then the guage should work. If nothing happens at all, the guage is probably shot, or there's a wiring problem.

Casey

[CleviteKid]

Thanx for your help, Casey. Re-reading my post, I should have written that my gauge starts at the bottom of the range and rises up to 150F as the engine warms up, but never goes over 150F.

I'm gonna try Casey's diagnosis to see if the gauge on the dash is OK.

Dr. Lee :cool:

[arveetek]

One more thing I might mention. When replacing the coolant temp sending unit, don't use any teflon tape on the threads. It might interfere with the unit's ability to ground properly to the head.

Casey