Restarting My '70 Nova Project

[BravoXray]

I was just getting ready to make a post.

Short answer, no I didn't find what or where the leaking voltage is coming from. I spent a few days with the dash out tracing wires on everything I could imagine was the culprit, but couldn't find it. I even set the cluster up and resting on the steering column, hooked up all the connections that go to it, and it didn't malfunction. I even ran a ground directly to the body, even though there are two other wires that provide hard grounds from the cluster to the body.
Then I finally went ahead in screwed it in place and the problem was back. Unfortunately, there is no room to get behind the cluster and disconnect the harnesses one at a time to try to isolate it. The only possible clue, even if it is related, is that the brake light comes on dimly when the key is in the accessory position, whether the parking brake is set or not. But, pulling the brake fuse makes the light go out, and the leaking voltage problem is still there.
One though I had today was if there is a possibility that the printed circuit that is on the back of the cluster, and carries connections to all the indicators and the gas gauge, might be the problem. So, I pulled the GAUGE fuse, and the problem goes away. Looking at the wiring diagram, there are no obvious points where the leak could occur, but obviously somehow there is. Also, due to the low voltage, that might coincide with the voltage to the gas gauge. Without draining the tank to see if the voltage changes, I might try disconnecting the sending unit at the tank harness to see if that affects the problem. If it does, that would tend to point to the printed circuit, maybe, so I might go ahead and order one and change it just for ***** and giggles. I just don't know.

Was a beautiful day here, so I pulled the Nova out and took it for a 30 mile ride around the area. It runs great, sounds good, and rides pretty good. It is a little noisy inside with the windows down, but I can still turn the radio up and hear it just fine. I even got a couple thumbs up from other drivers, which makes you feel good. In May, the cruise-ins at the Essenhauis start again on Thursdays, so I can make it to some of them this year.
When I got back to the house, I drug out the hose, filled the wash bucket with soapy water, scrubbed off all the dust, and rinsed it off. After drying it of, it looked a lot better.
I also opened the hood and turned the valve off in the heater hose, I forgot to do it before I went for the ride, but it really didn't put out any noticeable heat with the controls set to cold.
And best of all, no leaks!

So, when I decide to pull the dash out, again, I'll post an update.

 

[MossRoad]

Yes, it was a beautiful day!

 

[Alan46]

I was just getting ready to make a post.

Short answer, no I didn't find what or where the leaking voltage is coming from. I spent a few days with the dash out tracing wires on everything I could imagine was the culprit, but couldn't find it. I even set the cluster up and resting on the steering column, hooked up all the connections that go to it, and it didn't malfunction. I even ran a ground directly to the body, even though there are two other wires that provide hard grounds from the cluster to the body.
Then I finally went ahead in screwed it in place and the problem was back. Unfortunately, there is no room to get behind the cluster and disconnect the harnesses one at a time to try to isolate it. The only possible clue, even if it is related, is that the brake light comes on dimly when the key is in the accessory position, whether the parking brake is set or not. But, pulling the brake fuse makes the light go out, and the leaking voltage problem is still there.
One though I had today was if there is a possibility that the printed circuit that is on the back of the cluster, and carries connections to all the indicators and the gas gauge, might be the problem. So, I pulled the GAUGE fuse, and the problem goes away. Looking at the wiring diagram, there are no obvious points where the leak could occur, but obviously somehow there is. Also, due to the low voltage, that might coincide with the voltage to the gas gauge. Without draining the tank to see if the voltage changes, I might try disconnecting the sending unit at the tank harness to see if that affects the problem. If it does, that would tend to point to the printed circuit, maybe, so I might go ahead and order one and change it just for ***** and giggles. I just don't know.

Was a beautiful day here, so I pulled the Nova out and took it for a 30 mile ride around the area. It runs great, sounds good, and rides pretty good. It is a little noisy inside with the windows down, but I can still turn the radio up and hear it just fine. I even got a couple thumbs up from other drivers, which makes you feel good. In May, the cruise-ins at the Essenhauis start again on Thursdays, so I can make it to some of them this year.
When I got back to the house, I drug out the hose, filled the wash bucket with soapy water, scrubbed off all the dust, and rinsed it off. After drying it of, it looked a lot better.
I also opened the hood and turned the valve off in the heater hose, I forgot to do it before I went for the ride, but it really didn't put out any noticeable heat with the controls set to cold.
And best of all, no leaks!

So, when I decide to pull the dash out, again, I'll post an update.

You have more patience than most, my friend!

 

[Fuddyduddy1952]

This: "The only possible clue, even if it is related, is that the brake light comes on dimly when the key is in the accessory position, whether the parking brake is set or not." Is a major clue.
Of course no connection with parking brake and brake light. Is this a parking brake warning light or the brake lights?
If the car is all factory stock and a wiring schematic it would be easy to trace out...but I assume it's not 100% stock. Whatever has been added can cause weird problems.
Last summer I bought this '69 Rambler Rogue.
What sold me was it's originality except for aftermarket stereo which I replaced with a factory radio. Except for ignition, headlights and starter, nothing electrical worked. After 100(?) hours now everything works.
Any gremlin like brake light on dimly I focused on. The light(s) of course is getting voltage somewhere. It's a time consuming pain, but so nice when everything works properly.

 

[BravoXray]

Nice looking Rambler, don't see many of those around any more. I always thought they were a nicely styled car.

The harness is a total replacement harness from American Auto Wire. It is loosely wired similarly to the original, as come circuits have to be basically the same as original to work, but it also has many more circuits and options for retrofit options like EFI.
I am going to remove the dash again, as now the gas gauge isn't working and I want that functioning properly, and I have a new printed circuit for the instrument cluster as I think that may be the culprit.
I also think I might have a method to help trace down the backfeed source, it it works like I think it should, but, I'll have to try it to find out.

 

[the old grind]

I've found grounding to be a big cause of electrical phantoms (including with home/shop wiring) and esp with trailer wiring or with accessories added and no schematic updated or to update.

Dim and/or ghost lights, say when the key is off, is what makes us dig in. Accessories can ground through each other, and yes I've added diodes to grounds* to prevent backfeeding.

Edit: * per accessory vs per bus or attachment to body/chassis.

 

[BravoXray]

Thanks for the suggestion, but I was very meticulous about making sure everything was properly grounded.
The fact that there is a backfeed of ~3 volts into the accessory circuit seems to pretty much rule out a bad ground.

 

[Fuddyduddy1952]

One suggestion is something easy to fabricate. I was (still am?) an electronic repair tech 43 years before retiring years ago and had to think outside the box making "gadgets".
Harbor Freight sells a clip lead set for $2.99. Use that and inexpensive 16, 18 ga. lamp cord. Clips on both ends. Disconnect battery +positive, clip leads one end cable to battery post. Other end to a 12v lamp. Long enough lamp cord you can have that inside car (of course careful it cannot touch ground).
You use incandescent not LED lamp.
Now you have current-limited power. Limited by whatever lamp you choose. If you have a short, bulb burns brightly.
Last week a neighbor called, his trailer lights didn't work. I clipped truck frame ground to trailer framp...lamp lit. "It it supposed to do that?" he asked. Of course not. Truck to trailer had a bad ground.
If you have a parasitic current draw, light will light...current draw indicated by what lamp you use. A #194 is about 1/4A (250mA) while a headlight 3 to 8 amps depending on bulb.
For a short finder sub in a 2 prong flasher. You found short when clicking stops.