New electrical mystery. One day everything was fine and then it wasn't the next.

Symptoms:

Pulling the headlight switch to either position turns on the parking lights but does not raise the headlights or illuminate them. Oddly (I think) the foglight indicator in the speedo lights up when the headlight switch is in the first position whether the foglight switch is pulled or not although fog lights do not illuminate.

No horn, no wipers, no fresh air fan. Car starts and runs. It's a '73 that's been converted to a -6 years ago so there have been some modifications but limited to the engine compartment.

Emergency flashers work. Parking lights illuminate when turn signal switch is activated left or right. Turn signals work when ignition is on. Backup lights work.

I have 12v un-switched to the 3 fuses at the right end of the panel (headlight motors, emergency flashers & interior light and fog lights)

There is no voltage at either side of any of the other fuses - ignition switch on or off.

I've removed fuses and relays and cleaned contacts. Inspected wiring for breaks, bad connections, etc.. The headlight motors run if I jumper their relays.

Was hoping to figure this out on my own but I'm currently stumped. Any thoughts?

John,

oddly I have the same problem
I worked on it a tiny bit last weekend.
found my horn relay bad
fixed that and got my horn back

but 6 of my fuses (outboard to the car) are completely dead also
I will look again soon.. update you with anything
let me know if you find your problem please.

brant

Brant,

Well at least I'm in good company.

I have been pondering ignition switch but that wouldn't explain the headlights not going up would it?

Yes, please let me know if you stumble into a fix - I'll be sure to do the same.

John

Looking through my wiring diagrams... on a stock 73, the right 3 fuses are all fed by battery voltage.

Going left from there, fuse 9 is fed directly by the ignition switch in the run/start position (terminal 15), power also feeds from there to the engine relay board, and the ignition coil's terminal 15.

Fuse 8 is fed by the fan blower relay. The signal going to the coil to turn on the relay comes from the ignition switch when it's in the run position (terminal X.) That same wire also connects to the headlight switch on terminal 15. Terminal 15 bridges to terminal 56, which sends power up to the headlight motor cam switches, and the high/low beams.
Fuse 8 also provides power to the coil on the horn relay, as well as the blower motor, and windshield wiper motor.

Since your reverse lights work... and your car starts and runs... my suspicion is either in your ignition switch's X terminal, and/or your blower fan relay.

IIRC, on 1972-73 cars the little green light in the bottom of the speedometer is the indicator for the parking lights, and it is only on when the headlight knob is pulled out to the first detent. It's a reminder that you don't have your headlights on even though your instrument lights are....

As noted earlier, it could be the ignition switch "X" terminal. It may also be that the end of the wire that fits on that terminal has been pushed back into the plastic connector and is no longer making contact. Had that happen on an old Audi--took FOREVER to find. Might be worth a look.

Thanks much.

So the problem may actually be me and my understanding of how things work (no surprise there...)

When I was doing my testing, the ignition switch was in the "run" position but the car wasn't started and running. For grins I started it and with the engine running everything seems to work - well I couldn't hear the fresh air fan - but the lights, wipers and horn work.

Is this by design? I *thought* I remembered all of those things operating as long as the ignition switch was in the "run" position whether it was running or not.

I'm not aware of that making a difference unless the ignition switch is making contact after starting because the electrical contacts in the switch are landing in a slightly different position when moved counter-clockwise (Start to Run) rather than clockwise (Off to Run.)

If you move the key from Off to Run and slowly continue rotating it back and forth in the Run position, without starting, do those circuits start working again?

Nope. That was my thought as well. I tried wiggling the key around while in the run position and the light switch on and not a flicker. Only when it's running do those circuits work.

When i was putting my 73 back together and was testing things as i was building i had some very strange seemingly disconnected circuits light up and found out i forgot to connect the grounds. hooked up the ground lugs and all was good.
Anytime you have a gremlin unless there is obvious damage clean grounds first before wasting time tracing.
Hope that helps

So this raises two questions. Is the behavior I'm seeing the way it's supposed to work or should everything operate with the key in the Run position regardless if the engine is running? And if that is not the way it should work what is happening when the engine is running that allows them to operate? Maybe as long as they work when the engine is running it doesn't matter.

Point taken on always checking the grounds. Electrical things are pretty inventive when it comes to finding their own path to ground if a proper path isn't available. I have a melted emergency brake cable to remind me...

Off the top of my head... unless the alternator is backfeeding power when it's running through the gen light (which should just feed power back to fuse 9, not 8) or the ECU is backfeeding power (which again I think if anything in that realm were possible it would be fuse 9, not 8, and shouldn't apply in your case anyway because it's a (I assume carbureted) -6...) I don't know how anything would be able to detect that the engine was running, at least not on any of the diagrams that I have.

John

Any further updates?

I found 2 of my problems so far but still not running

I’m very curious if those outboard (for me it’s 6 dead fuses) only have power when the motor is running

My 6 fuses are still dead as are all 4 of my fuel injectors
Even though I fixed my horn wipers cig lighter and fresh air fan

Injectors? Does the fuel pump run?

yep.

fuel pump runs
(front relocated, so not all stock wiring, but I believe I added to the stock wiring and still use the fuel pump relay)

starter motor turns over, spins the engine well
I verified I do have spark with a spare plug
and verified that all 4 injectors are silent with a noid tester
didn't measure fuel pressure, but do have high pressure in the fuel lines when I loosened the cold start valve

so fuel to the injectors
just not exciting the injectors to get them to open

Not to hijack this thread, but I have a similar issue; air box fan, wipers and lighter all are run off a jumper wire from the fuse box. It’s not been a problem but the question is

Does a single relay exist for all these?

Thanks

Brant,

No updates. I have sort of filed it as "if it's not broke don't fix it". But those fuses only have power when the engine is running. Whether that's as designed or not I don't know. This car has had lots of different hands in there over the years so it's hard to say.

John