Temperature gauge needle goes all the way to the right when lights are turned on.

[gaC5]

On my 78 when I turn my lights on the light goes out on the temp. gauge and the needle goes all the way to the right.

 

[gmjunkie]

On my 78 when I turn my lights on the light goes out on the temp. gauge and the needle goes all the way to the right.

You have a high resistance or non-existent ground in the car somewhere!
Anything acting goofy besides the gauge light and the gauge?

 

[LLC5]

On my 78 when I turn my lights on the light goes out on the temp. gauge and the needle goes all the way to the right.

Like junkie said, bad ground at the gauge......

 

[gaC5]

No. Just the temp. gauge.

 

[gmjunkie]

No. Just the temp. gauge.

Then pull the center gauge cluster and find it. There is a bad connection there somewhere!

 

[frank_nesta]

Then pull the center gauge cluster and find it. There is a bad connection there somewhere!

it does not sound like it is the center connector, but I would start there and make sure the connector is well seated. Then to the temperature gage. Check the connections by loosening them and retighting them taking care not to over tighten them. Check to see if that corrected the problem. Good luck.

 

[SwampeastMike]

I'd check the printed circuit very carefully. Pay particular attention to the "ears" at the end of traces where they contact the main connector. A study of the printed circuit diagram makes me suspect that if the top two "ears" on the side where you see the 2nd wire down heading directly to owest terminal of the temperature gauge are touching that it would do exactly what you experience. Also check the traces very carefully in the region of the temperature gauge as those printed circuits are known for delaminating. When that happens traces can touch one another.