Gauges stop working when lights are switched on

[DENNYSCARS]

 I am fairly confident that the issue is related to a ground somewhere or lack thereof.  My question is, where?  I have the column ground strap secured.  When the lights are off the gauges work fine.  When I switch the lights on, parking or headlights, the gauges just "go to sleep". Looking for a little HELP!:shruggy:

[DENNYSCARS]

Anybody have any input?0

[b5blue]

Pull the plug on the dash dimmer control. (?) Possibly you feeding +12V to the gauge ground. 

[DENNYSCARS]

Hey Neal, thanks for responding.  How would that happen?  Feeding back through the dimmer?  You may be right.  This morning when I started up and switched on the lights the gauges all pegged out.  Then the fuel gauge and temp gauge went to zero (left) and now without the lights on don't appear to work anymore.  Oil pressure still functions.  This after I finally got the fuel gauge reading correctly.

[b5blue]

I'm thinking (wild ass guessing is more correct) instrument lights feed shorted to circuit board for gauges somehow? 

[Chryco Psycho]

test the ground for the dash lights to be sure it is not going into the guage power circuit

[DENNYSCARS]

Thanks Chryco, 
I assume there is a separate ground or is it grounded to the cluster frame?

[b5blue]

Check the 5V gauge voltage regulator and it's circuits for shorts to gauge lighting somehow. 

[Chryco Psycho]

As I recall the lights are in a circuit board so it will have to return to the wire plug to get ground , the gauges ground down to the senders so the power from voltage reg has to be interupted between the reg & gauges when the lights are turned on . Maybe one of the wires in the plug to the dash in in the wrong position orthe worng wire connected to the volt reg ?

[Calif240]

One idea that may help further identify the root cause... take a small piece of masking tape and cover only one of the terminals of the headlight switch. Plug the harness back ensuring that one terminal won't make the connection. Now start the car and flip the switch. If the gauges don't "sleep" when one wire is blocked, then you'll know the root cause is somewhere in that circuit as opposed to one of the other two. May save you some guessing on where the actual problem is coming from.