344670

Hey Guys.

I got an electrical short on the right side of the fuse. The battery power side into the fuse box is fine, but I have a short to chassis after the fuse. This is the cigar lighter, clock, glove box lamp, trunk, trunk light, dome light, courtesy lights, door lights, main lamp switch etc. Before I start ripping and isolating each leg, is there a know grounding spot you guys are aware of for me to look at and try to get lucky??? 1970 A body 442.

oldcutlass

Try unplugging the cigar lighter. It may also be related to your tach installation.

344670

I did earlier today. No change. The outside of the lighter is grounded but not the hot middle part. The bad thing about this ground its that it blows fuses right away. As it should.

344670

I metered the tach brown/shielded wire this morning. The sheild is not shorted to chassis and the brown wire isn't either.

Fun71

Does the car have a maplight mirror? I had issues with the power lead for that touching the mirror housing because the plastic insulator section broke.

Another thing to check for is the dome light screws. Have heard of cases where a screw was put through the power wire.

oldcutlass

The shield is supposed to be tied to ground at one end. Double check or undo any wiring mods you've done recently.

344670

Im working little by little in isolating the legs. I had the center console opened up today and checked the two bulbs and the lid switch. Seemed ok. I metered both in ohms and connectivity to ground and both where coming up as shorts. My one lead is on the right side of the fuse box as the left side is hot (from the battery). I also checked the fuse box with power on and a test light mimicing the fuse. Nothing lights up. I don't have a dome light but I have two back seat side walls lights that I can't open up.

oldcutlass

Using an ohm meter to trace this will drive you nuts because of all the light bulbs. If it worked before your changes, it was something you introduced.

344670

This is a nasty big circuit. Here's the kicker, I've had the car going on 20 years. I bought it this way...... Nothing on that circuit has ever works since I've owned it. I checked the door switches and the glove box light and the trunk push button. Plus that whole circuit, all is acting normal. Tomorrow I'm unplugging the clock. See if that makes a difference.

Texas69

FWIW, check the trunk light and the map light above the radio. I had shorts at both points.

The map light was easier to diagnose since it messed up the interior courtesy lights.

The trunk light wire got pinched under one of the clips that attached the wire to the trunk lid. This was not obvious until the wire was removed.

Good luck! Wiring issues are unpleasant to chase down.

344670

Very nice. I do not have a trunk light. Should it? Does all 4 doors, 2 doors and convertibles card have a trunk light? The schematic shows it but the car doesn't have it physically right now. What side of the car does the wire run down in?

344670

Also, there's 4 wires under the hood I haven't figured out of that circuit.

One red wire off the power side of that fuse. Three on the accessories side. A blue wire, a beige wire and another brown wire. All 4 of these I have no clue what they do.

Would the hot all the time red wire be for the mercury switch for inside the hood? That's missing right now on my car. But the other three, I have no idea. If they're not supposed to be on this circuit, there's the issue. Might be grounded thru the bulkhead kinda thing.

344670

The under hood light shows on the brown circuit in the schematic. That's the park light circuit. So that red always hot wire from the accessories light that is under the hood can't be for that.

What's the purpose of those 4 wires?

MDchanic

No wire from the CLK-LTR-CTSY fuse is red, and none goes forward of the firewall.

The schematic is pretty clear:
Blue: Turnsignals, Wiper Motor, and oil pressure
Beige (Tan): Low Beams and Brake Warning Light
Brown: Parking Lights, TH400 Kickdown


As far as the problem at hand:
Have you checked the dome light? I had one once where a dome light mounting screw was piercing the insulation of the orange wire, causing a dead short. That was tough to find.


- Eric

Fun71

I suggested that and this was the reply:

MDchanic

Oh.

Could be them.

Maybe should open them up.

- Eric

344670

I haven't found it yet. I don't have a trunk light. I'll try to find those wires. This might be a winter project. Might need to start looking with power on......