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Temp Gauge

Last summer my '87 250 overheated and the temp needle pegged. Everything settled down and no damage done. However my temp gauge now never drops below the "l" in normal. Is there any way to fix this? Is it stuck and could it be moved back or is it truly buggered? Is just the temp guage available as I don't want to replace the whole cluster.
 

DNFXDLI

The Token Canadian
Staff member
Have you tested the sender?
 

DNFXDLI

The Token Canadian
Staff member
Resistance check...of course I'm not sure what the resistance should be when it's cold...big help huh?

The way to check it is to disconnect the wire from it and use a meter from the stud to the body of the sender (ground) and see what the resistance is.

I might have a manual that specs the resistance, I will look...or hopefully someone else chimes in.
 
Resistance check...of course I'm not sure what the resistance should be when it's cold...big help huh?

The way to check it is to disconnect the wire from it and use a meter from the stud to the body of the sender (ground) and see what the resistance is.

I might have a manual that specs the resistance, I will look...or hopefully someone else chimes in.

Thanks for the assistance regarding the resistance. Electrical is not my thing.
 

DNFXDLI

The Token Canadian
Staff member
NP :)

If the sender fails it will give you wonky readings....I have the same issue with my RV generator.....gauge read about 220 to 230 under normal operation...shot it with an IR gauge as saw 170 as the hottest. I checked the sender, resistance reading wrong.
 
I just checked the sending unit per the Chilton book, un-plugging it and nothing changed. The needle points actually just to the left on the red area. I will try the IR reader and see what that says. The engine is not overheating but that needle bothers me.
 
Well I ran the engine for about 3/4 of a hour yesterday doing some errands. Took my IR gun and it read 180* +/ so th engine is not overheating. However, th gauge needle when cold is just to the left of the red line and when up to operating temp well past the red line. I unplugged the wire from th esending unit and no change. Any ideas on how to get th eneedle back to where it should be when engine is cold.
 

Fellro

Moderator
Staff member
Try grounding it. Open circuit makes a reading one direction, grounded is the other. The sender is a variable resistor.
 
...th gauge needle when cold is just to the left of the red line and when up to operating temp well past the red line... Any ideas on how to get th eneedle back to where it should be when engine is cold.

Only way I know to do that is open up the gauge itself but I've never done it on that truck.
 

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