Instrument Panel Grounding
Many people over the last 20-some years have called here with this same basic question: “Something is wrong electrically with my instrument panel lights and gauges. I have removed, restored, and reinstalled the dash frame. Now, lights don’t light right, the alternator gauge isn’t reading right, the turn signals don’t work right, and none of the small gauges work. What is wrong?”
When you removed the instrument panel frame, blasted it, nicely and thoroughly painted it, and reinstalled it into the also nicely painted body of the car, you forgot that the dash frame, and the instrument cluster, and the switch cluster, and the steering column must all be well-grounded.
Notice the bolts with the huge free-spinning washers on the extreme lower corners of the dash frame-to-body. One, if not both, of those washers must have a bare, clean contact to the dash frame. The washer itself must be grounded to its bolts, and the bolt must be grounded to the car body via its threads.
The instrument cluster must be grounded to the dash frame. Originally one or more of the tabs that receive the instrument cluster mount screws was bare metal. That allows cluster housing contact to dash frame.
Cars with a separate switch cluster, or separate individually mounted switches, must also be mounted so there is a ground contact. This is especially true for the rheostat that controls the dash illumination level and the dome light and console lights.
You might get lucky by simply running the screws that mount the clusters in and out several times, instead of removal and cleaning paint.
The car body itself must be grounded, as must the engine. On older cars, a heavy wire stranded cable connects the engine to the body firewall. This must be a true ground, not just eyelet pressing onto the paint of the firewall and engine paint.
Later cars have an auxiliary cable from the battery negative cable to the car body. There are some requirements here as for engine-body. If this cable is not truly grounded, bizarre conditions will exist throughout the car’s electrical system.
A final note about park lamp bulbs, tail lamp bulbs, and brake lamp bulbs: If you install an incorrect bulb, or install it backwards by forcing it into the “foolproof” socket, or have a defective bulb, you will have bizarre light operation.
Some bulbs may go out when the brake pedal is depressed, or some may get brighter that should not.
Also, a defective turn signal switch and/or an ungrounded steering column may be the cause of these conditions. A thickly-applied interior paint job may cause a poor ground, not just no ground.