Well here's a good question!

[Afflyer]

Late yesterday afternoon, when I drove home from the base, I went to turn on my parking lights and I noticed my aftermarket Autogage tachometer dropped from 2500 RPM to 1500 RPM!  My oil pressure gauge also began to peg out to the right.  There was no difference in engine performance, just what those indicators said.  The indications went back to normal, when I turned my lights off.  Now this is wierd.

Any ideas from the electrical experts here as to how and why this happened?

Thanks in advance fellas,

Bradley

[Chryco Psycho]

where are you getting power for your guages ?
the load of the lights on that power circuit is probably dropping voltage to the guages

[Afflyer]

The power for the gauges is where it normally comes from.  The only thing I've "rigged" is the aftermarket tach, and it's wired exactly as the directions say it should be.

This was just the first time I happended to notice the load differences when the lights are on.

Is this normal?  It just can't be, as far as I'm concerned!

[Chryco Psycho]

definatly not normal , how is your voltage regulator?

[Afflyer]

This is sure to sound like a really STUPID question, but where exactly is the VR located?

[Nacho-RT74]

if he is talking about the cluster voltage limiter is a square silver box plugged on back of cluster.

If he is talking about the Voltage regulator itself is located close to center top of firewall, on engine bay

[Chryco Psycho]

plugged or bolted onto teh rear of the dash

[Plumcrazy]

If it was the voltage regulator for the gauges all of them would have pegged to the right.

Just the oil pressure gauge pegging to the right could be the gauge,sending unit or wiring.
How the gauge,lights and tach seem to be tied together is strange.

Maybe try disconnecting the tach for a while and see what happens with the oil pressure gauge.

[myk]

Speaking of aftermarket 'tachs and wiring, who runs them and what brand did you buy?  Also, how would you plug the 'tach into the output terminal of an MSD?  Is there a pre-made connector included with the 'tachs or do you have to make one?

[nh_mopar_fan]

Has the wiring ever been hacked?

I'm having sort of the same issue with the wife's Signet ragtop. The temp gauge works fine until you turn on the lights and then it pegs. I haven't played with it for a couple of weeks because I've been dealing with the fact that the tranny pee'd all over the garage floor last week.

That was finished tonight so I have to get back to the wiring now. My harness has had an issue in the past and a couple wires have been fried including the fusable link. All have been replaced and they all appear to be correct.

I have no idea what's causing this now....

[nick_iam]

sounds like the headlamp wiring is shorting to the gauge wiring.. 

[nh_mopar_fan]

Yeah, or the switch. One of the replaced wires was a wire off the headlights.

One more thing top Afflyer, if your gauge is pegging, avoid running the car with the lights, you will burn out any gauge that's pegging.

[Ghoste]

Also, is the tach a recent addition or has been functioning normally with the tach up until now?

[71_deputy]

sounds like the ground in the dash or to the frame is not the best. add a wire from the dash frame to the body!!!

[MorePwr]

I'm thinking a bad ground also