Tim81

I have owned my 81 since 2006 and have been very lucky that I have not had any electrical problems. Well, I think my luck just ran out, when I turn the headlights on my Alt, Oil Pressure and Fuel gages drop all the way to the left, when I turn the lights off everything returns to normal. The draw on the battery is just over 14 volts with the headlights on or off. Not sure what to make of this but I'm leaning toward the headlamp switch. Any help would be greatly appreciated,

Thanks Tim

Marlin

Could be a bad ground/loose wire in the gauge cluster.

When you turn the headlight switch on the only thing it should do to the gauges is turn the dash lights on. Extra power is going there and needs to ground out. Or to much power and shorting out as well.

Do the gauges do this when you turn the parking brakes on but not the headlights?

...Roger...

Just guessing but I would think the gauges have lost their ground and are now back grounding through the INST lights (dash lights),when the dash lights are turned on the gauges loose their ground.
The gauge cluster shares a central ground with many other items,so that central ground is most likely ok. I would be looking at the large plug at the back of the cluster to see if one of the thin brass contacts is not making contact or the printed circuit has burned in 2 at some point.

Tim81

Well, I think you guys are on the right track. I have notice that it only happens when the dash lights come on. I also found out that if the dimmer **** is turned so the dash lights are at their brightest the problem goes away, when I slowly turn the dimmer **** counter clockwise the dash lights get dimmer and the gages also start to move ccw until they are all the way to the left. Guess I'll have to check the circuit bwd on the back of the cluster for some breaks or burns.

Thanks Tim

Tim81

Ok I think I'm making some progress, I reseated the connector on the back of the speedo/tach cluster and now the gages seem to work, the only problem is now my gage cluster does not light up. When I turn the **** on the light switch CW the lights in the speedo cluster get dimmer and when I turn the **** CCW the speedo lights get brighter, not sure if this is correct it might be working backwards.

Any ideas Tim

thiatt

Ccw is brighter till dome light comes on if I remeber right. Certain thr direction that turns on dl is brighter

Tim81

Good night tonight, found a broken trace on the gage cluster circuit bwd thats provides the ground for the fuel gage. Repaired the trace and everything is back to normal. Thanks to all of you for your help.

Tim