I have a semi-bizarre problem (although my Land Rover discovery did this as well)...

On my '73 914 2.0, the oil temp gauge read high, when the headlights are on. My car runs at about 210 degrees (I have a mechanical gauge on the dipstick), at that temp the oil temp gauge shows about 220. Which is fine, not sure which is more correct, but they are consistent. But, when I turn the headlights on, sometime the oil temp gauge goes up to close to 260. As soon as I turn the headlights off, it will return to indicate 220, so the oil isn't really increasing in temp.

So, is that fixable? Is it likely to be a ground problem?

Thoughts?

You answered your own question. Ground problems


Geoff

Is this a stock temp gage? You might want to look at the graound as suggested, or figure where the plus 12 volts is coming from. If it is an add on gage, maybe it is getting its 12 V from a say the headlight fuse???? If so there will be a voltage drop when lights are on.

Check with a volt metet the voltage on the gage. Check with the voltmeter ground on the gage ground, then recheck with the voltmeter ground on a good body ground. If there is a difference between the two readings, then it is a ground issue, so re-ground your gage. (do this test with headlights on)

If not the ground, then find a better +12 v supply to power the gage, but do not forget to have it fused.

good luck

dave