[lav]

I own a 1966 GTO. I live in Canada where the winters are long and cold. While returning the car home from the winter storage location I noticed the battery indicator light on my instrument cluster on very dim. Because it was a cold day I switched the heater on. Nothing heater dead. I then tried signal lights . Nothing signal lights dead. Brake lights dead. Wiper washers dead. Instrument lights dead. Working on the car is headlights, running lights, interior lights. The car needs a tune up but it ran ok. Not Knowing much about electrical. I started at the battery and put it on a load tester and the battery seems ok. Next I installed an old voltage regulator I had kicking around voila the the battery light went out; but the aforementioned electrical components still DEAD I have cleaned all ground copper straps in my sand blaster and they look like new. Cleaned all ground contact points 1) Battery to block 2) frame to fender 3) block to firewall. Tomorrow I am going to install a new alternator and new voltage regulator. I went to the fuse box cleaned all terminals.
removed fuse box to look at back for corrosion it looks like new. I wired a jumper to my battery and fed 12V to fuse box and all "dead" components working fine. the voltage at the Dead fuses is about 1-1.5 volts. Any help would be greatly appreciated.

[stuta]

Don't ya just hate those electrical gremlins !!

Seems like you have done your homework on "what to look for" with this problem...but something still isn't right.
Here's a curve ball for you...maybe some little critter chewed a wire or two while in storage?! You've cleaned off most connections. What's left is the question.

Ignition switch maybe, or the fuse block itself.
What's strange is the separation of what is working, and what was dead before you put the wire on.

Good luck my friend

[george kujanski]

Sounds like the main splice or fusible link is bad so you are not getting power to the fuse box as you determined by using the jumper. It's usually in the taped wire loom that runs along the intake side of the driver's valve cover around cyl 5&7.

George

[lav]

Originally Posted by george kujanski

Sounds like the main splice or fusible link is bad so you are not getting power to the fuse box as you determined by using the jumper. It's usually in the taped wire loom that runs along the intake side of the driver's valve cover around cyl 5&7.

George

Not 100% sure what the main splice or fusible link is but I will send photos to you George. Maybe a good time to replace engine harness? Does the fuse box get its power from this main splice or off of the ignition switch somehow?

["QUICK-SILVER"]

I'd be looking for a bad connection of the accessory wire on the back of the ignition switch.

Might be able to just wiggle the wires on the back of the ignition switch and get things working again. If it does... terminals in that connector will need cleaned up, tightened up or replaced.

Clay

[Chris65LeMans]

When I bought my car, I found out that the rear lights didn't work at all. Turns out that the "pigtails" (the electrical connection to the light bulbs themselves) were bad. The dash lights did work, however.

Someone mentioned the engine harness - I'd suspect the under dash harness first - although I wouldn't spend that money right off the bat without some more tinkering.

As I remember - the headlights are on a different circuit from everything else. I think the "running lights" are what we call the "parking lights" down here. I didn't know they were on the headlight circuit, but I guess that makes sense. Also didn't know the interior light was, but it appears that yours is.

I'd guess that the same issue is causing all of your outages. This is good news, but I've unfortunately only got hints for you - not a map.

[george kujanski]

The dash power goes thru the fusebox generally from the main splice as mentioned. If that is defective, the fuse box gets no power. You effectively bypassed the defective section with your jumper.

See the attached wiring diagram for a '67... the black with double red stripe wire from the splice is the wire that feeds the fuse box.

[lav]

I want to Thank all for responding to my Electrical Problem. I took George Kujanski's advise and removed all tape from wire bundle that runs along drivers valve cover. I then discovered the "main splice" or "fusible link" which in my case was a corroded mess. Looks to me like the wiring was butchered in the past. I have put in a call to Ames to have the engine harness replaced. For now I just used a large Butt type of connector to see if this was the problem and YES all electrical functioning as it should. Again thank you all and a tip of the hat to you GEORGE KUJANSKI Check out photos of old splice job

[OG68]

There's another splice behind the dash IIRC.
The splice on the valve cover feeds this second splice through the firewall as a Red wire. The second splice then feeds the headlight switch, ignition switch, and fuse box.

[Chris65LeMans]

Good info!

[Peter Serio]

Back in the early 1980s when these cars were first considered as a possible future collector's item. The first reproduction harness they made was the engine compartment harness. I think the sale price back then was around $95 or $99.

Any 50+ year old GM car that you plan to drive around should have the engine compartment wiring replaced just for preventative maintenance. Those photos are a great example of just what happens to old car wiring!!