Gauge grounding issue

Last night took the vette out for a ride and when I turned on my parking lights (and headlights) all the gauges grounded out (pegged lowest readings)  except the temp gauge.  It shouldn't be the light switch since i just installed one over the winter.  Before i tear apart the dash for the 5th time i wanted to make sure it is not something in the console.

I do have the schematics and the circuit for these gauges is the same for the console lights but the lights work fine.  Any thoughts are appreciated.

--Eric

It's a bad ground from the gauges.  They are grounding through the light circut, but when you turn on the lights, the ground becomes a hot and the flow stops, and the gauges drop.

You can vary the gauge readings by turning the dimmer up and down.  Try it.  When that happens, fix the gauge ground.

I had the same issue when I first bought my 73. The PO had installed a new radio and didn't hook up the ground properly. I added a ground wire to the back of the gauge cluster and everything is fine. Redwingvette38502.2444791667