Installed new Pro-Sport oil and water temp gauges a week or two ago. I've noticed that there seems to be some interference coming from somewhere. Applying the brake or turning on the headlights moves the needles on both gauges up by 5-10 degrees. Turn off the radio and the needles move down a little. Both sensors are grounded to the engine, and both gauges are grounded to the body.

Any ideas? Body to engine ground issues? It's not a huge deal, I know, because I can compensate in my head... but this really shouldn't be happening in the first place..

 

Any takers?

 

Where are you pulling the power for the gauges?
Seems like you're getting unregulated +12v.

 

bad grounding from battery to body and engine most likely.

 

The gauges are pulling power from the audio deck.

 

Checked, cleaned, and ran new grounds today... no luck...

 

Could a smaller than usual battery cause this? Or perhaps something to do with the alternator? I've got 14 volts at idle..

 

Radios produce quite a bit of EMI. When I removed my radio, which my A/F guage was also attached to, no more weirdness from the A/F guage.

Attach the gauge to a switched ignition wire at ignition switch harness.

 

I had literally this exact same problem as you, and it was bad grounds. Make sure you clean ALL grounds. The worst one I found, that seemed to help the most, was the ground block on the back of the drivers side shock tower. It has 4-5 male connectors on it (if memory serves) and a white connector that connects on to them. Take it totally off and clean everything. Also make sure that you totally dissasemble all of the battery connections and clean inside them. There can be a lot of corrosion inside the connectors that you can't normally see.

 

Cleaned up my grounds. There's a ground block on the backside of the drivers side shock tower??

I'll try a separate power source too.