Recently when I have my headlights or parking lights on my gas and temp gauge spike and also my dash lights flicker.My headlights,tailights etc seem fine.Just my dash .

Here is one pic.

I put the same pic twice.The temp gauge is spiked and I only have less than a 1/4 tank of gas.If I turn the headlight switch off they both go to normal readings..

my guess is You have a ground issue to the instrument cluster/ dash or at the lights.

Check the body ground. Some have a smaller wire from the neg battery post to the body and some have a ground from the body to the eng and some have both. Make sure the body ground is good first as that can cause problems like that. Ron

take a long wire & clamp one end to the batt neg post & touch the other end to the dash mounting screws one at a time & see if it straightens out

As mentioned, body ground problem. Same thing happened on my 72 Satellite. The front lights were getting its ground through the instrument panel instead of the harness. One of the instrument panel turn signal lights was also dimly lit. The front harness ground can get corroded or break causing the problem.
Craig

My 67 coronet has been doing the same thing.. All of my grounds are clean ( I have two extra grounds on car).

It was recommended on here to ground the instrument panel with a ground strap..

I have not done it yet.. At 61 crawling under my dash just doesn't excite me too much anymore.....

There is a problem with one, or more of the parking light grounds, probably on the front of the car. Engine off, turn on the parking lights and see which one is not lighting up, or is more dim then the other. Gene

As mentioned, body ground problem. Same thing happened on my 72 Satellite. The front lights were getting its ground through the instrument panel instead of the harness. One of the instrument panel turn signal lights was also dimly lit. The front harness ground can get corroded or break causing the problem.[/quote]



"The front harness ground",is this the two black wires that are coming from the headlight wireing and grounded together on the front,i don't know what to call it,radiator support? The connection there is solid and clean.

I also tried using a long wire grounded on the battery and touched the mounting screws in the dash and no change.

I will get some pics sunday when the sun is out.

Alright if we are sure the cluster has good continuity to ground, I'm wondering if there is a prob on the supply side, (that fire from the dash lights that get turned on when you turn the headlights on) is somehow bleeding over & full fielding the gas/temp gauges (giving them full 12V) & making them peg. I hate to do it but I would pull the dash & grab your meter. Actually first I would pull the HL bakelite connector off of the HL switch & pull the wire/terminal for the dash lights then replace the connector on the HL switch & turn the lights on & see if the prob goes away. EDIT female packard 56 terminals have a tang on the back side & go in the back side (where the wire is) with a mini eyeglass screwdriver & depress it & when it is flattened enough the the wire/terminal will EASILY pull out the back side & if not dont force it then go back in with the screwdriver