Wiring Madness AKA "take it in the shorts" 1972 type3

[hambone]

I have various electrical issues I now need to address on the eternal 1972 Squareback.
There is a short, one of the fuses melts (intermittently) upon starting the key. Wiper motor is affected.
I also do not have turn signals, instrument lights, or high beams. The headlights work, but the instrument light (green, for headlamps) will only illuminate when the running lights are on, as soon as the headlights are turned on the instrument light goes off. Someone has also rigged in the incorrect flasher relay and I need to return it back to stock.

I am studying the wiring diagram like a madman, tracing lines. I know that current flows only one way, but how can you tell the direction of the flow from the diagram? For example, wires going into the fuse box - which way do they pass thru the fuses (up/down or down/up)?

How the HELL do you trace wires (like the flasher switch) that are damn near impossible to see, due to the dashboard or clusters of other wires? While you are upside down, using a trouble light?

Finally, what is the easiest process for determining a short? Is it a matter of painstakingly tracing each individual wire to it's source, or should a meter be used?
I'd imagine the battery must be disconnected for this sort of work.

Thank you, I am in up to my ears in this stuff. For some reason, electrical and Algebra make my brain shut off.

[dtrumbo]

There is a short, one of the fuses melts (intermittently) upon starting the key.

Which fuse? I need sumpin' to go on.

The headlights work, but the instrument light (green, for parking lamps) will only illuminate when the running lights are on, as soon as the headlights are turned on the instrument light goes off.

This is correct by design. Your bus does (or at least should) the same thing.

For example, wires going into the fuse box - which way do they pass thru the fuses (up/down or down/up)?

I wouldn't fret yer perty little pate about current flow. That's an argument all to itself. For now, just figure out if the wires you have are connected to the correct places and don't connect to places they shouldn't (see the next quote).

How the HELL do you trace wires (like the flasher switch) that are damn near impossible to see, due to the dashboard or clusters of other wires? While you are upside down, using a trouble light?

You just described the best way. C'mon, you wouldn't want to cheat yourself (and your back) out of this better-than-sex experience!

Finally, what is the easiest process for determining a short? Is it a matter of painstakingly tracing each individual wire to it's source, or should a meter be used?

Yes. As miserable as it appears on the surface, the electrical system on these cars is actually very easy to work on. I know you're ready to choke the livin' s*** out of me for saying that, but compared to a "modern" car which wires are nearly impossible to trace, these are relatively easy. Tracing each wire from point 'A' to point 'B' and verifying that they jive with the wiring diagram is the first step. Then you can use your meter to "trace" the other wires you can't physically ring out (like from the fuse box to the front and rear lights). Here's how: With your meter on the 'ohms' scale put the red lead on the wire in question and the black lead on a good ground. If the wire is shorted to ground, your meter will read nearly zero ohms. Unless the wire is, in fact, a ground wire (typically brown) this is probably not what should be happening. In the case of a lighting circuit (headlamp, turn signal, marker light, etc.) the meter will read a small number of ohms (but not as small as zero) as it's reading the resistance of the filament in the bulb. Remove said bulb and the meter should read open or infinite ohms. If with the bulb removed you still get a small or zero ohm resistance then that wire is shorted somewhere.

I'd imagine the battery must be disconnected for this sort of work.

For continuity checks (ohm meter work) yes. Once they're all rung out and you've fixed any shorts or opens (shorts are wires incorrectly connected to ground, opens are wires that don't connect to anything), reconnect the juice and see what's what.

I hope this helps. Yes, Colin. Technical writing isn't as easy as it looks.

[RSorak 71Westy]

My suggestion on the short is to forget following every inch of wire until you checked all the splices and connections that wire has. I short rarely occurs in an open run of wire, but more frequenty at a terminal or another connection.

[dtrumbo]

My suggestion on the short is to forget following every inch of wire until you checked all the splices and connections that wire has.

How do you find all the splices and connections without following every inch of the wire? Ideally, you'd look at the wiring diagram and check the factory locations. However we all know previous owners are evil, very evil.

[Amskeptic]

My suggestion on the short is to forget following every inch of wire until you checked all the splices and connections that wire has.

How do you find all the splices and connections without following every inch of the wire? Ideally, you'd look at the wiring diagram and check the factory locations. However we all know previous owners are evil, very evil.

There are useful connector diagram/lists on the later ladder diagrams. Best way to guess if you have found the one you are looking for is to count number of wires in connector and see if they jive with the diagram's promise, and catch enough wire colors to verify as well.

The early drawing diagrams are easy for tracing but do not show you locations nor functions.
ColinYesTechnicalWritingIsNotEasyAndPOsAreEvil

[hambone]

Very helpful, thank you Dick. Do the wires have to be disconnected to check for shorts, or do you just check it at a convenient junction?
How strange that the direction of the flow of current isn't important for this troubleshooting.
Also strange that the green dash light should shut off when the headlights are on. Seems counter intuitive.
The melting fuse is 3 down from the top, 16a:

I will let you know how this goes! It's a big loose end that I must address and can't afford to pay someone.

[hambone]

Man I've got shorts everywhere...at or near 0 ohms from wires going from fuse, to steering column, to wiper motor, and @ the motor soldered connections. Either I'm doing something wrong, or this wiring is a dreadful mess. There are also a few spliced wires that disappear into the body etc. that aren't original - and they have shorts too.
There is also a small box with 4 connections @ the wiper motor, not shown on the wiring diagram. Radio noise suppressor? I hope so because 1 of the soldered connections was poor and fell off.
I have no idea where to start...I have traced wires without any obvious melting or visible shorts.
I hope I'm just doing something wrong!

[sped372]

Calm down, don't panic! One at a time. I've had good luck checking for shorts to ground by disconnecting *both* ends of the wire and checking for continuity between the wire and a good chassis ground. Otherwise sometimes I'd get confused by having *some* continuity because the wire is technically connected to ground, albeit through a load (bulb, etc.). Once you get the hang of it things will speed up... if you jump around before you're comfortable you'll just drive yourself nuts. Be methodical!

I believe the green dash indicator is to let you know that *only* the parking lights are on.

[dtrumbo]

What sped sed. To minimize the freak out, remove all of the bulbs and disconnect any motors (if possible) and then check everything. The filaments in the bulbs and the windings in the motors can sometimes appear as dead shorts when they're just the appropriate load.

I have no idea where to start...

Yes you do. That that add-on box near the wiper motor is the perfect place to start. As the other half of the diagram you posted shows, Mr. Nordoff (and his subjects) envisioned your wiper switch to have four wires attached to it. Not coincidentally, the wiper motor has these same four wires attached. Since the fuse that blows is the one that protects the wire that supplies power to... wait for it... the wiper switch AND the wiper motor, I'd be suspect of one or both of these items. Since you've already discovered evil P.O. add-on's near the wiper motor, that's where I would start. If it were me, I'd restore the wiring from the switch to the motor to the original vision and see how the 16amp fuse fairs.

So as not to overlook anything, that fuse also protects the wire that supplies power to the switch that controls your fresh air fan. Although I'm leaning toward the add-on box near the wiper motor, you should be aware of this potential cause in case the wiper circuit all checks out and the problem persists.

Don't pay anyone but yourself with the sense of accomplishment and furtherance of your knowledge.

[Amskeptic]

So as not to overlook anything, that fuse also protects the wire that supplies power to the switch that controls your fresh air fan. Although I'm leaning toward the add-on box near the wiper motor, you should be aware of this potential cause in case the wiper circuit all checks out and the problem persists.

That fan gets drowned in the air plenum when it clogs with junk. Mine was a disaster of rusted barnacles and wiring strands rusted to clips.

Utterly baffling to me, is that the fan still works with one of the through bolts still busted in half and all that rust and peeled insulation shellac.
Colin

[hambone]

Thank you guys.

Hey I now understand why I was getting grounding everywhere,thanks for the clarification. The circuit completing itself.
I always took the early wiring diagrams as schematics, not road maps. A big mistake!

Kirk came over and gave me a hand yesterday. A big help! So, the emergency flasher switch (behind the metal dash of course) one day long ago split in 2, neatly with no damage except to randomly short against the said dash and blow the fuse. Well, someone in the past thought it was a good idea to bypass this unknown problem and plumb in a hack job flasher relay right into the main line without fusing, and of course fixing nothing. And of course they used cheapo aluminum wiring with useless rubbery insulation, with the wires just twisted together at the junctions. Oh my.
The hack wiring is gone and now I have to reconnect the neatly snipped ends to the multi-pronged steering column plug. A mess, but at least the original wiring is still intact and relatively undisturbed.
The emergency flasher switch has been zip-tied back together and it looks like it will work, God knows.

I am not holding hope for the fresh air fan based on the amount of debris pulled from the hood grille crap-trap. Apparently they are anemic anyway sour grapes.

Also have to re-run that burnt wire that powers the back tail lights. Crispy, right into the harness...

[hambone]

The snipped wires have been joined to their long lost mates. I was excited to try it!
But, the emergency flasher switch causes a fuse to blow. It does click the relay a few times first.
And, apparently that sub-wiper motor box is part of the speed control, because I only have power on the high setting, and it doesn't park anymore. Also replaced a couple broken grounds, but I still don't have instrument lights.
This car is a never ending fiasco. Is that flasher switch bad after all?

[Amskeptic]

The snipped wires have been joined to their long lost mates. I was excited to try it!
But, the emergency flasher switch causes a fuse to blow. It does click the relay a few times first.
And, apparently that sub-wiper motor box is part of the speed control, because I only have power on the high setting, and it doesn't park anymore. Also replaced a couple broken grounds, but I still don't have instrument lights.
This car is a never ending fiasco. Is that flasher switch bad after all?

No, the switch is not necessarily bad, it is sending electricity to a downstream problem. Do not piss off the switch.

No park is often an inadequate ground. High speed only means the low speed circuit has an issue. Park has its own power supply independent of the switch to run the motor until the circuit is mechanically interrupted at the park position.

Fiasco is too hard of a word. It is a sweet patient car waiting for us to resolve the errors of others.
Colin

[hambone]

Does this independent power supply look like 1/2 a cig pack with 4 wires going to the soldered wiper motor terminals? If so, a green wire fell off and could be the problem with the wipers. Can I just re-connect it, or will I then have to reset to "park"?

I only say "fiasco" because every system has needed intense attention. Don't forget, I've been working on this car full-time since the end of June. I am ready to be done! But thank God for all the help I've received, trying to understand this stuff.

[Amskeptic]

Does this independent power supply look like 1/2 a cig pack with 4 wires going to the soldered wiper motor terminals? If so, a green wire fell off and could be the problem with the wipers. Can I just re-connect it, or will I then have to reset to "park"?

I can't tell you. My Squareback's wipers have never drawn attention to themselves.

If your park feature comes back and is not synchronized with the wipers/linkage, you can sometimes loosen the crank on the gearbox, run the wiper motor and shut it off, then put the crank on as horizontally opposite the wiper arms at rest position as you can figure out.
Colin