Electrical mystery (at least, to me)

[bobswei]

On my '72, I recently did an engine rebuild and new paint, glass out, everything apart. I didn't touch the electrical system.
Afterwards, first thing I noticed was the dash lights were always on. Key out of the car. I replaced some bad bulbs, now ok, Except the clock light is on when all others are off. Turn the lights on, dash lights come on, clock light goes off. For now, that bulb is disconnected. But now there is a battery drain. After a day or so, the battery losses it's charge. It's a new battery. When I remove the ground cable, it stays charged. So, I used a test light from ground cable to battery "-" post. It lights up. I removed every fuse, one by one, then every relay, one by one. Unplugged engine wire harness and anything else I could find and the test light, always lights up. I've owned the car over 20 years, never had an electrical issue. I never touch the wiring (other than unplugging lights and plugging them back in for painting. Also, new original steering wheel and horn. But, I think removing the fuses would have uncovered anything in there.
Any ideas on where to start?
Thanks

[tirwin]

My thought is to check the wiring at the ignition switch and headlight switch. It sounds like something isn’t wired correctly or maybe something got jostled and is making contact. Dash lights come on with headlights/parking lights. That is an unfused circuit. When you pull headlight knob to the first detent that is providing a path to ground. Check switch function, wiring and the ground.

[Bob Kontak]

Originally Posted by bobswei

Any ideas on where to start?

Did you "pull" the fuses and relays in the engine compartment?

I know you unplugged the wiring harness, just thinking out loud.

[Dave Colangelo]

Few things to check,

1. Everything went back onto the fuse panel correctly
2. If you did paint, check the grounding points. They may have been painted over and when you reconnected the grounds are not making proper contact with the chassis.
3. Stripped wire case, its possibly you stripped a casing and caused a short while reinstalling stuff.
4. Crossed wires.
5. Missed connections on reassembly.
6. Make sure all your wires are connected to the proper terminal for what they are not necessarily the color. Over the years mechanics have a habit of using what ever wire is lying around so not everything is always true to colors in the schematics

[ossiblue]

Originally Posted by tirwin

My thought is to check the wiring at the ignition switch and headlight switch. It sounds like something isn’t wired correctly or maybe something got jostled and is making contact. Dash lights come on with headlights/parking lights. That is an unfused circuit. When you pull headlight knob to the first detent that is providing a path to ground. Check switch function, wiring and the ground.

My thinking is along this line as well. The lights all share the same circuit and are wired in series, so it doesn't make sense that the clock light goes out when the others come on, and vice-versa, unless there is a foul up in the connections. Also, there is a light in the ash tray that is wired in the same series that could be causing the battery drain if it is on like the clock light was.

[bobswei]

OK, great suggestions. Tomorrow or Tuesday, I will remove the light switch and check each connection one at a time. Kinda makes sense since it began with the dash lights.
Yes, I did pull the fuses in the engine compartment and the relay back there. Unplugged both sides of the electrical panel there also. Didn't think about the ash tray or know there was one in there ('72). I did have the fuse panels removed (un-screwed but not disconnected) in the trunk and did have a screw cut a wire when reinstalling but fixed that.
Updates to come soon, hopefully.
Thanks, Bob

[bobswei]

Today's update: I backed the light switch out of the dash and disconnected each wire, one at a time and checked my test light. Lights up on every one. I also revisited the clock and found out I switched the positive and ground wires which explains the lighting issue. Must have plugged it back in without my glasses on. Anyway, then went to the horn and disconnected the connection under the steering wheel. Not it.
I wish there were some heat seeking, x-ray goggles that you could turn out the garage lights and see a glowing wire running through the car.
Oh, on reassembly, every wire and ground connection was cleaned and or wire wheeled.
I'll update again when I learn something new.
Thanks.....

[Knockdown]

Not x-ray goggles, but a digital multi meter would be able to give you more information than the test light. With the DMM, you could measure the amount a current that is being drawn from the battery, and with the fuse removed, measure the currents being drawn by the individual circuits. If you are unsure if the current being supplied by the battery will exceed the max current that the DMM can measure, you can place a power resistor between the battery and positive cable, something on the order of 10 ohm, 20w, and measure the voltage across the resistor. If you get 12v across the resistor, then the resistor is limiting the current to 1.2 amps and you can use the DMM to start tracing down where the current is being drawn from.

For some extra bucks, you can also get a probe that works with a DMM that measures the current in a wire by just clamping the probe over the wire, not x-rays but magnetic field

[tirwin]

I believe the OP said that he has pulled all the fuses and the draw is still there. That implies that the draw is on one of the unfused circuits. I’m not familiar with the circuits of the ‘72 but that would point to headlights, dash lights and ignition in most cars.

Bobswei, glad you found the backwards wiring at the clock. Now look for similar at the headlight switch. If dash lights are on with headlights off and key in off position, then wiring is backward. The headlight/parking light should complete the ground for the dash lights when the headlight switch is pulled to 1st and 2nd detent. If they are on all the time it means the dash lights are being grounded all the time. Pulling one wire at a time will not tell you anything. Check the color coding of the wires to the terminals on the back of the headlight switch. Two wires are in the wrong position.

[SpyderMike]

If you found a power and ground switched at the clock, that could explain your drain. Now that you have fixed that, is your clock running correctly - keeping time?

[bobswei]

So, I made some progress today. The comments on the "clock" got me thinking. A while back, it had a battery drain that I discovered was the top fuse in the trunk. It fed the dash lights but replacing bulbs, I thought, fixed it. The clock was working OK. Today, I pulled out the top fuse and looks like no more drain. Oh, and I'm using a digital meter this time. Wiring diagram shows "no" black wire coming out of the number 1 terminal (on the right side). But I have one.
So, now I'm back to the original issue with the number 1 fuse. I will do more experimenting tomorrow. Here's the pix of the issue areas:



Thanks for the input and getting me in the right direction.

[ossiblue]

Look at this diagram, its for a 73 which should be like your 72. You will see the black wire coming from #1 fuse and going to the clock (69), etc.



Use this link to access the 73 wiring diagram and legends.

http://www.pelicanparts.com/911/911_Parts/911_electrical_diagrams.htm

If you had a drain from fuse 1, the clock is surely part of the issue as it's always powered. However, it should not be enough to drain the battery in short order. You can trace the feed from 1 by following the diagram to the various devices, including the light in the glovebox. The clock is the only device that should be constantly using power from fuse 1, so unplugging the connector from the clock should let you know if something else in the circuit is causing the drain.

Oh yeah, don't forget your trunk light. It may be on without you knowing. Open the trunk and depress the button switch near the passenger side hinge and see if the light goes out or, to be certain, disconnect the wire from the switch or remove the bulb. Same with the glove box light. Keep in mind the glove box light is a rocker switch like the interior lights. It's possible that it may be in the always ON position and you don't know.

[SpyderMike]

He hasn't suggested that he still has a problem draining the battery. When the clock was hooked up backwards, he had power shorted to to ground which would have drained the battery fast. He went back and fix that connection mistake, and that could have solved the problem. Now the question is - does he still have an abnormally high drain?

Also, I asked if the clock ran properly. When he powered the clock up backwards could some damage be done to the clock resulting in a higher than normal power drain? He hasn't answered that question yet.

Just guessing here.

[bobswei]

Sorry Spydermike. I was trying to get to all the main ideas and the clock "was" working ok. But tonight's trial and error session shows that the clock may be the culprit. When I disconnect the power to the clock, no voltage going through that circuit (ground wire disconnected). I reconnect the power wire to clock and I have 12.4 volts going through the same circuit. I thought the clock did not draw power continuously but every minute or so to wind it so it will continue without having to have a constant 12 volts? Yea? no?
I did check trunk and interior lights and all are working fine. Actually, the trunk light is not connected yet.
I'm replacing some transmission parts right now so the engine is out. Once back together, I can drive it and check to see if the battery stays alive with the clock disconnected. Then trouble shoot the clock, if so.
Thanks for all the input and saving the day, once again...
Bob

[SpyderMike]

No worries Bob...just trying to help get you to the finish line as soon as we can. I am pretty sure that my clock is powered and draws current all the time.

[timmy2]

Clocks are always on and running. On a constant power circuit along with the trunk lamp and glove box and interior lights. I can always hear mine when sitting in my car parked in the garage and it is quiet.

[Flojo]

Originally Posted by timmy2

Clocks ... I can always hear mine when sitting in my car parked in the garage and it is quiet.

yes.. tshirp, tshirp, tshirp... actually quite loud these are.