Electrical Gremlin?

[1966Belvert]

Hello everyone!

With the shorter days upon us, I've found myself having to turn on the headlights towards the end of my last couple of cruises. In both cases, after I turned on the headlights, the temp gauge started to climb and was almost in the danger zone by the time I got home. I'm thinking that this is likely an electrical issue and that the temp really isn't rising, but I haven't had a chance to start digging into it yet. I'm hoping this group can help me narrow my search. Thanks is advance for your thoughts and ideas!

Steve

 

[Builderguy]

I am assuming a single wire temp gauge. The engine block acts as the ground, the resistance of the sensor (changes with temperature changes) is sent back along this single wire to the gauge.
When you turn on your headlamps something in the grounding system is changing. IIRC as the coolant heats up it lessens the resistance. So if something in your headlamp wiring is causing a better ground to the block, the gauge will show this as a temperature increase. Maybe??? Sure someone will have a better answer.

 

[pnora]

Simplest thing you can do is check the actual temperature with a laser pyrometer. Then you can deal with it if it is an actual problem. Until you do that it is a guessing game.

 

[493 Mike]

Fan belt slipping?
Mike

 

[Don Frelier]

What does the gauge do if you turn them off?
Suddenly drop, slowly drop or no change?

 

[1966Belvert]

What does the gauge do if you turn them off?
Suddenly drop, slowly drop or no change?

I tested this while driving in the day light yesterday. When I turned the lights on, the temp gauge began to slowly rise towards the danger zone. When I turned them off, the needle began to slowly drop.

 

[Don Frelier]

Do you have a block to firewall ground strap on the rear of the engine?
Try removing it, hit it with a wirebrush and reinstall.
You can also try a jumper cable as a test from the battery - to a good clean body ground bolt.
See what happens.

 

[Sixpactogo]

Poor connections and bad grounds are the major causes of electrical issues. A digital Ohm meter is almost mandatory. Anything that should be grounded should test out at less than .05 ohms. I suspect your engine ground or possibly your gauge cluster ground not up to snuff. If they both test good, I would go to the wire connections.

 

[black64]

Like the others have said it sounds like a ground issue. But it only occurs when you turn the lamps on. Try pulling the panel lamp fuse and turn on hd lamps to see if the temp gauge slowly rises. Bad ground creates these type of issues.

 

[mopar 3 B]

If this is factory in the cluster gauges check the cluster ground.