Voltmeter wonky after water temp gauge install

[cscmc1]

Alright, folks, I've about worn out the search function trying to wrap my mind around this one. I have just installed an Autometer water temp gauge, and now my voltmeter reads in the yellow even with the key off. If I pull the water temp gauge out (so that it's no longer making contact with the metal panel that the voltmeter mounts in), the voltmeter goes back to normal.

What the heck? I'm not seeing any bad grounds or contacts anywhere. This is driving me nuts!

Thanks in advance!

 

[cscmc1]

To clarify: I am seeing ~24 volts measured on my multimeter when the metal panel that the voltmeter is mounted in is grounded. It's as if the ignition key is turned on when the grounded water temp gauge makes contact with the panel.

I have seen others mount mechanical water temp gauges in this location and it doesn't seem to cause an issue. Any ideas? I'm at wit's end here!

 

[cscmc1]

FINALLY found a post describing a similar problem:

http://www.steelsoldiers.com/cucv/53946-another-volt-meter-prob.html

How are folks installing gauges in this panel w/o causing this issue? I'm perplexed now. Guess I'll need to figure out a way to insulate my gauge from the metal panel, huh? Strange...

 

[cscmc1]

To follow-up: i have the gauges working correctly now. I did indeed need to isolate the water temperature gauge from the metal panel it mounts in, as allowing it's housing to contact that panel grounded it, and sent 24 volts to the voltmeter. It appears that the ground to the voltmeter is what is switched with the ignition via the relay.

Anyway, I opened the hole for the water temp gauge up just a bit more with a dremel, and used some narrow window channel ($.20 per foot from Ace Hardware) to line the opening and insulate against the body of the gauge. The clip that secures the gauge in place, though, is also metal, so I folded thin rubber from some tubing over the ends and electrical-taped them in place. This allows the gauge to be secured without grounding to the panel.

Everything is working fine now. Hope this helps someone!

 

[JGBallew]

FINALLY found a post describing a similar problem:

http://www.steelsoldiers.com/cucv/53946-another-volt-meter-prob.html

How are folks installing gauges in this panel w/o causing this issue? I'm perplexed now. Guess I'll need to figure out a way to insulate my gauge from the metal panel, huh? Strange...

By using aftermarket gauges with nonmetallic bodies and isolated grounds?

Just a guess.

 

[cscmc1]

By using aftermarket gauges with nonmetallic bodies and isolated grounds?

Just a guess.

I wondered whether that was the case, but several photos seem to show the same gauge I used. On closer inspection, though, some of the pics seems to indicate that the voltmeters in those trucks might be dead; they are WAY to the left, further than mine ever reaches. Maybe they just never noticed the interference since they never had working voltmeters to begin with (?).

In any case, thanks for the reply!