Gauges die when I turn on running lights 1980 l-82
 

Noticed this issue a few days ago and have been scratching my head all week.
Stock 1980 l-82, with car running I pull headlight switch and amp meter goes to zero and stays there. Clock stops, fuel gauge slowly drifts to E, temp gauge goes to zero.
First thought is bad ground. Checked all sockets and found less than one Ohm to ground on running lights.
With engine off, amp meter slams from 13 to zero as soon as I pull the headlight switch out.
With lights off amp meter reads 13 volts and all other gauges function normally.....
Any suggestions would be appreciated. Maybe a bad switch? Gauge reads fine without lights on so figure gauge isn't faulty.
Lights come on when switched on.
Driving me crazy:crazy::crazy:

Still sounds like a bad connection or ground. I would look at the connector that plugs into the gauge cluster. The tabs get loose and cause these kinds of problems. Straighten the tabs and plug it back in carefully.

Will check the ground to the cluster tomorrow and repost. Thanks for the feedback

Pulled the cluster. Tabs look nice and flat/straight and no sign of arcing or corrosion. Measured ground at pin 150. Five ohms normal and increases to nine ohms with the light switch pulled. Traced the runs on the printed circuit and it all looked good. No rips or tears.
Put it back together with no improvement.

Frustration leads to progress.... Discovered while cussing and looking for a bigger hammer that if I turn the dimmer all the way down on the headlight switch, I can turn on the headlight swith no problem...... Sooooooo
Now I am apparently looking for a short in my interior lights??? As I adjust the dimmer the amp meter ( and all the other gauges in the cluster)will still dive at a point but when I dim the interior again, all the meters return to normal. Would have thought the radio and other dash electronics would die. Still doesn't affect any exterior lights.
Ever hear of that?
Tried attaching a ground wire directly to pin 150 to see if it made a difference. Same results.
Thinking it may be in the switch? Other possibilities?

The lights in the gauge cluster are fed through the interior light circuit. It is pretty obvious from the symptoms that voltage is being passed to something in that circuit that is not supposed to have voltage on it. My opinion is that the ground to the circuit board is bad somewhere and when voltage is put on the lamps it raises the voltage on the ground circuit to the point that the gauges will not work. It is a classic symptom. Check the ground side when the lights are on. If it shows voltage, you can go looking for that ground.

Hey Wayne,
After two weeks of getting kicked in the nuts by this thing, I got it beat. Took your advice and went to the connector, would like to kick the guy who designed that thing..... Any way, little corrosion on the tabs. Cleaned and straightend those. Three tries at trying to get the connector in with the tabs straight, finally nailed it. Lowered the resistance but had to keep going. Wound up cleaning the contact points on the potentiometer on the dimmer circuit (2ohm pot was giving 30-90 ohms erratically, figure that was enough to develop the voltage upset.
Anyway goes to show clean connectors are happy ones and guys who do this day in and day out can point out the high failure items.
Thanks for pointing me in the right direction.