Join Date: May 2005
Location: Denver, CO (SE)
Re: Grounding issue?
It may well be a grounding issue. It might also be a voltage issue with the dashboard's power supply.
Can you nail down when it happens?
1) Does it happen when it's cold, or when it's warm (outside)?
2) Does it happen before or after the dash has been on for awhile?
If you think it is temperature related, you can check it with a hair dryer. That can heat up a given connection really fast; don't overdo it. Trace back until you find the one that flakes out under heat. You can also use freeze mist (or, actually, just a can of compressed air used to blast dust out of a computer held upside down) to cool down a junction to below-zero very fast. In general "cold solder" joints will have thermal problems.
3) Does it happen when the dash gets vibrated?
4) Does a good smack to the dash help? Those tend to be connectors underneath screw heads that are making intermittent contact.
Tracking down stuff like this can be difficult and make people invent entirely new swear words. You may have, for example, a flaky fuse, or oxidation on the fuse contacts, in the fuse box.
I've had stuff like this happen, and I finally adopted a "overkill: stomp the bugs flat" approach that usually nails it down quickly.
What I usually do when this sort of thing happens is bring two wires from the battery, +12V and Ground. Fuse them BOTH AT THE BATTERY in case you run into a nasty short. You can find some easy inline fuses at Radio Shack. 5 amps is plenty. Bring the wires through the firewall, with some tubing around them at the firewall to protect them from being sliced there. Tape over the ends of these two wires when they are not actually connected. You really really really do not want a live +12V wire to battery +12V flopping around. Trust me. The cloud of blue smoke you get when it shorts out is something else.
Fire up the car, and one at a time, connect these two wires to the power and ground for the dash, as -close to the dash as possible-, again, -only- when the dash is already powered up. (If you power up the dash with the ignition off, the power will backfeed to the ignition switch and turn other things on, and that can turn ugly in a hurry.) Tape the connection; it's only temporary.
If the dash stabilizes while either the dash +12V is connected to battery +12V, or while dash ground is connected to battery ground, there's your problem. hat you can do now is follow the dash pwr and ground back and find the place where adding +12v or ground doesn't help anymore; between that point, and where it does help, is your problem.
I hope this helps.