Bad ground

[framedoctor]

If anyone has experience with bad ground, any info on how it was resolved or where it was found would be greatly appreciated. If I turn headlights or blower on, the gauges pin out.

[Taylor]

I checked, re checked and re checked all the grounds. Replaced what looked questionable. Then I rewired the headlights with relays, so they would draw power directly from the battery. Not because of the dashboard lights dimming. The big problem I was having was the low beams were not bright enough and I didn’t want all that power going through the headlight switch causing it to over heat and potentially burn out or cause a electrical fire.

[Illeagle1984]

Well the blower motor is case grounded (has its own ground), so I don't think it's a ground problem.  What does it mean, the gauges 'pin out?'  Do they stop working?  What do the instrument cluster lights do?  More information please.

If you have a test light or multimeter, it will help a lot.

[MIPS]

The main engine-to-body strap failed on me once. Because the ignition system and the computer grounds through the block the engine ran but when you applied loads through the body (EG: the headlights or brake lights) it would try and ground itself through anything it could find back to the engine, such as through the rear diff, the driveshaft, the T-case and transmission and finally the engine. It also tries to backfeed through the temperature sender and for example you stomp on the brake the gauge pegs.

[framedoctor]

Thank you for the response. I did replace engine to body strap with a heavy duty battery cable. I actually thought it fixed the issue but the issue soon returned.

[framedoctor]

So when I say pin out what happens is all the gauge needles move fully clockwise to max position.

[Trooper]

Check the ground on the firewall in the engine bay between the back of the motor and the brake booster.

[framedoctor]

I know that is one that I removed and sanded and reattached. I was in fact moving wires around in that area the other day and the problem temporarily was gone. Maybe the ground wire to that spot is cracked enough to cause issue?

[Taylor]

If you were moving them a round and the problem got better, temporarily. It could be that there is a bad wire in the harness somewhere. Possibly a housing that hardened from heat and allowed water/moisture in causing corrosion. When I did my ECM Test bypass I checked all the wires for insulation hardness and any corrosion on any connections. If I recall, it took me at least a week working a couple hours a day to check all of them. I always double and usually triple check my work.

[Illeagle1984]

I have had good luck using jumper cables to find bad engine/body grounds.  Just put one set from body to engine, and the other from engine to battery.  If the problem goes away, you're barking up the right tree.

You can also use a test light in kind of the same way.  If it lights up from body to engine, that ground would be suspect.

[framedoctor]

Good news, problem found. At some point, someone removed the ground wire from the ground stud behind the brake assist and moved it to a spot with a self-tapping screw. It was getting an intermittent connection. I had to add length to the wire and reattach it to the stud. all is good.

Thank you to everyone who helped with suggestions. Mips, Canoe, Taylor, Trader, Illeagle, Trooper

The car was for my son from his grandfather. Now he can drive it.

[vangremlin]

Great to hear you found the problem!  And that is a really beautiful Eagle!

[Taylor]

Thanks for the update.
Great looking Eagle.