Electrical issues

[Peter T.]

I have a zwitter that I restored 25 years ago. I cleaned, restored and replaced every electrical component including the wiring harness. When I turn on the headlights there is a voltage drop that effects the wipers and semaphores. I've had it checked out by a few mechanics and I ended up rebuilding the generator which helped a little. I also checked the voltage at the headlight switch and fuses and it all checks out 5.5 volts or better.
Any thoughts?

[AndrewCologne]

Did you check all terminals/contacts?
Also ... when you restored your car so many years ago, .. did you solder all ends of the wires? If yes then this can be the guilty one as solder becomes soft during the years and you will get into problems with bad connections.
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1950 Split Window Grey
1955 Oval Window Stratosilber
1982 Porsche 911 3.0 SC Black

[Peter T.]

This has been a total mystery. I had two vw mechanics check it out.
I didn't solder the ends, but I'm thinking maybe the new harness could be the problem. One mechanic told me to try to find NOS headlight bulb holders and new bulbs.

[Suboval]

Are you running your windshield wipers and semaphores with the engine running or off?
If off, try it with the engine running. Normal voltage should be ~6.4 VDC.

The fuse block and headlight switch could both be affecting the wipers and semaphores.

Solder the connections on the back of the fuse block to ensure no high resistance.

Headlight switches can also have high resistance. Take it apart and clean the contacts and re-grease.
_________________
It all works on paper.

There's two things we learn from history:
1.) History repeats itself.
2.) We don't learn from history.

[ZENVWDRIVER]

[Peter T.]

Totally appreciate the input. I'll give ideas a more thoroough try. I've already gone through the headlight switch and the fuseboxes and found no resistance. I also run the motor with these issues still there. If I rev the motor over 2200rpms it helps. Still haven't thoroughly checked bulbs and bulb holders.

[0nebadbug]

[johnshenry]

[Zwitterkafer]

X2 ^^

Checking tightness of all screw terminals and quality of wire ends should be an annual "Service" item on all screw terminal cars. The solder itself is not the problem, they came that way from the factory. Good to avoid acid core solder though, when making repairs....the copper strands inside an insulated wire can oxidize badly but remain undetected.
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"Criticism comes easier than Craftsmanship"
- Zeuxius, 400 BC

[vwoldbug]

Do you have a spare voltage regulator you can try . Have you tested the generator by grounding the field wire with wires disconnected with engine running .

[Peter T.]

Just had the generator rebuilt and regulator tested by a "Bosch" guy, generator is putting out 6.5-7 volts. I have had this issue going back 23 years when the repro harness was new so wire corrosion doesn't seem to be the issue....rusty threads?
I just thought of running a thread tap into anything that is holding something electrical.

[johnshenry]

I wouldn't be concerned about the screw term thread contact,but you could run a small round file through the bore that the the wire goes through.

If you want to get technical, you can use a volt meter (DC volts) and some clip leads and "hunt down" the voltage drop. I'd start the car, turn on the headlights then measure the voltage right on the battery terminals for reference. Then (you'll need to make one very long clip lead) measure the voltage between the pos term at the battery, and the positive wire terminal at whatever device you are trying to find the drop for, headlight, sem (when on) whatever. In an ideal situation, you'd get 0 volts, no drop. But there is always some.

Now start moving the lead back from the device, toward the battery. Measure from battery + to the next terminal point to that device, probably either a switch or a fuse holder. Keep working your way back toward the battery in the circuit and not the values.

Say you see a 2 volt drop at the sem + terminal (its the lower one, black/white or black/green wire there. Then at the sem switch term you get .4 volts, then at the fuse box you get .2 volts, then at the big red wire term on the back of the headlight switch (I think, I don't know Zwitters wiring as well as I know split dashes) you get .1 volts.

That would tell you that most of the drop is 1.6 volts lost between the sem switch and the sem. So suspect either the wire or term connections. Clean the term connections, if that drop is still there, then it is the wire. Verify it by using your really long clip lead and "jumper out" the sem wiring, clip right on the sem switch then around the side of the car to the sem on the other end?

Make sense? Tedious, but I have done this in the past in tough situations where voltage is getting lost somewhere in the car.
_________________
John Henry

'57 Deluxe
'56 Single Cab

[Brezelmeister]

Ground straps !

Make sure to check them, specially the one between gearbox and chassie,
Bad ground can cause all sorts of weird trouble.

[Grant Reiling]

[Peter T.]

Ok I finally got around to cleaning and replacing the ground strap from the transaxle to the chassis. Made everything better and brighter. The semaphores still struggle a little with the lights on.
I checked the generator and its putting out 7.3 volts so I was thinking about putting a thinner ground strap from the generator to the body.
Any thoughts?

[wimkever]

[Peter T.]

So it seems that I solved the electrical issue with running an extra insulated generic cable from the trans to the chassis.
What is the functional difference between a generic battery cable and the OEM braided cable?

[DDub]

One had a good connection, the other did not. Put an ohm meter on it and check resistance.

[Peter T.]

resistance checks out good. Just wondering the difference between the braided cable vs a insulated cable.

[johnshenry]