using test light for locating ground faults theory --rant

[2type2]

Per the times on utube vids--"Wiring in a test light across fuse contacts acts as a fuse but lights up in a ground fault condition, since it's drawing the current on path of least resistance to the faulted ground (short) and once faulty ground disconnected light will go out"

I get it, it works easy right? Well my method is faulty or my brain is gone- what I have tried is removing all connections to the suspect circuit --first at fuse box end, also tried at the terminating end ( ie: at:tail /head/parking lights). Despite systematically disconnecting and checking all ft park lights, then rear lights all at one and also by indiv circuits, there is no change. Fuse blows - -from #58 at headlight switch-- no matter what. Early harness has no relays and only 8 fuses. 65 bug
After 3 days of pulling my hair, I'm afraid I'm just going to go back to other work like doing upholstery, so then I will end up with a completed project I can't drive due no brake lights or other. Saving the worst for last--- not my idea of enjoying a hobby.This is the kind of thing that totally sours my love for working/owning/driving these little machines. F it, rant over
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"A life of peace and happiness depends on your own gratefulness"

[busdaddy]

A test light is too low of an amperage to differentiate between normal circuit loads and a short, a sealed beam headlight bulb is the better lamp for this job.
So remove the fuse, wire a sealed beam to the now empty fuse terminals and start connecting things to the circuit, when the headlight bulb lights you found the short.
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[Heiferman]

@2type2 - sounds like me and carbs.
I have a fair amount of "luck" with wiring, metal work, body work and stuff like brakes but carb stuff has always given me hell. I could put a carb together step by step with an expert and mine would not run right. It has been this way since I was 16 - 40 years now.
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- 1973 Thing, 1970 Ghia, some LandCruisers and an old Ambulance

[EVfun]

Light switch terminal 58 powers your tail lights, license plate light, and your front parking lights if they have been changed to stay on with the headlights. Terminal 58b powers the dash lights (using a gray striped red wire), so be sure it's 58 and not 58b that is causing your trouble.

The gray wire from 58 goes to the fuse block and powers 2 fuses, the one right where it connects and the one next to it closer to the end of the fuse block. Which of those fuses is blowing? Next test is to see if that wire, that runs to the back of the car, has shorted out somewhere.
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[2type2]

-I have the connections noted set that way. Have disconnected front park lights to eliminate them as suspect. Def an issue at 58. I have disconnected everything both individually L&R, also as complete circuits. Best method for check of full length front- to- back wire?
Blows fuse that is sixth over to R from Driver side(usa): ( is that #3 or 6 ?)
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"A life of peace and happiness depends on your own gratefulness"

[EVfun]

[busdaddy]

[2type2]

I'm aware of all that about fuse removal.. I was initially disconnecting the 58 circuit at end by removing the bulb,no result, then disconnected gray wire only at tail light.no change. I'll go back to the junctions one by one, disconnect at each. But I don't have a tarboard in and had cleaned up the wiring.Hopefully it's near the end, or my alternative is to rewire the main harness section from trunk to engine bay , Likely to get to it today, but wife sees me getting tension and suggests we " go do something entertaining ", so good
I do really appreciate the feedback---- sometimes I get frustrated and it makes me lose patience, then interest.
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"A life of peace and happiness depends on your own gratefulness"

[EVfun]

If the gray w/black stripe wire running from the front to the back is shorted out along its length an alternative to replacing the wiring harness is to run both tail lights and the license plate off of the circuit next to it. Fuse #2, the gray w/red stripe circuit next to it is also powered by light switch terminal 58. The 8 amp fuse can easily handle it.
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[VW_Jimbo]

Your comment immediately makes me think of several Bugs I have worked on with oddly reacting rear harness issues. ALL OF THEM turned out to be a past fried wire issue.

Many Bugs have burned up their coil feeder wire from the ignition switch. This feeder sits in the same body lol as all of the wires that need to reach the rear of the car. When this feeder burns it melts and fuses (sorry could not help the pun) the wires within the loom, into melted insulation and oddly connected circuits.

Might be worth a look at the harness going down into the cabin and the rear portion by the ignition coil. If they have melted loom insulation or burned up remnants of wire, it might be time for pulling some new wires!

Hope it is not any of that! But it was the first thing that went through my head.
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Jimbo

There is never enough time to do it right the first time, but all the time necessary the second time!

[2type2]

Happy Memorial Day, I wish? Got excited w learning able to run rears alternatively on gray/red side ( i presume thats good also if need for running both off gray/black?). So wanting to see what long wire specifically, first I disconnected license light then ran a jump wire (disconnected gr/rd at fuses and test with jump, then tested gr/blk.Running direct from fuse block terminal to rear bay terminal. Well the 3 fuse position still lit up the test light proving still shorting.
I'm no good at this. I'ld go have a beer, but been sober since '23, sigh
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"A life of peace and happiness depends on your own gratefulness"

[busdaddy]

[EVfun]

[2type2]

Understood and already done. What I did exactly was in this order-
Disconnect license light from harness. Unplug red/grey at fuse panel, unplug red/grey at junction in engine bay, BEfore taillight wires.Run jumper from fuse panel to engine bay connection. Fuse replaced w test lamp. Still lights when powered by switch.. Then..... did the same process to gray/black wire starting at fuse panel, same no good result.
So my thinking was --" if the jump wire resolves it then the short is in the long section and I can rewire that length to solve it". Not getting a positive result doing the bypass on both circuits leaves me lost. BTW the interior is stripped, park lght wires at front disconnected entirely, no tarboard, so the harness is very visible and accessible all the way.
Should I try another head light switch? Just thrashing about the shop
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"A life of peace and happiness depends on your own gratefulness"

[EVfun]

A bad headlight switch will not cause a fuse to blow. The headlight switch is not fused. Fuses only blow for an overload or short circuit that occurs after them in the circuit.

So, if you disconnect the gray/black and the gray/red at the fuse box and put the fuses in and turn on the headlight switch neither fuse should blow because there is nothing connected after the fuse. If it still blows that would suggest the fuse block is somehow shorting out to the body.
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[2type2]

Evfun- thanks for coaching me along on this , it's not been a joy. Disconnected both gray/red and gray/ black at fusepanel , replaced all fuses. Pull switch -- #4 fuse Blows! (yellow to R headlight).
And while replacing the fuses I heard a crash- --- the mirror glass fell out of drivers' mirror, no real signs of glue.



Every little thing is gonna be alright every little thing is gonna be alright every little thing is...
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"A life of peace and happiness depends on your own gratefulness"

[2type2]

OK I jumped from fuse terminal 4 to the R headlight and it works without blowing that fuse. I'll replace that length. I wish that jump wire had.resolved tail lights issues.
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"A life of peace and happiness depends on your own gratefulness"

[EVfun]

Looking at the 2 pictures of your wiring harness, I'm impressed that it isn't very molested by previous owners over the last 60 years. The output side of the fuses are toward the front of the car, the power inputs are to the rear.

I see 2 wires connected to the output of fuse #2, the gray/red one on top and a small gray one pointing forward. The gray one is most likely your front parking lights, it is a modification I do to old Bugs and I didn't invent it. Stock US spec older Bugs have unfused front parking lights and a tendency to burn up those wires. If fuse #2 doesn't blow you can go ahead and reconnect those 2 output wires and verify that circuit works as it should. It should power the right tail light and I'm going to guess the front parking lights too.

Is there any chance that any of the disconnected wires could have made contact with any part of the metal bits above or in front of fuse #4? This is a new fuse to blow so somehow it saw something new drawing power through it. I sometimes have to tape exposed terminals out of the way or stick them inside the fingers cut off a latex glove. Those wires are stiff and old and they like to slowly move back after being disturbed, usually while running around trying to test the circuit!

I'm thinking that we want to establish what works and what doesn't work and what fuses blow when everything is connected normally (as your pictures show). Any fuse that blows after everything is put back the way you started will be left out for now, there are problem in that circuit after the fuse. Then we work from there, chasing individual circuits after their fuse, to simplify things by allowing us to ignore most of the wires and focus on just 1 or 2 at a time. When done the circuits will be working and the wiring will largely follow the VW schematic (and we know what changes have been made, and why).

Here is the 1962-1965 model year US Bug wiring schematic:
(The light switch is item F, the ignition switch item D.)

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[2type2]

I have previosly removed all ft park light connection from fusebox to eliminate them as a possible problem. Yes the connections are generally unmolested and I also cleaned all contact points. I'm about to install a new R headlight and check for both hi /low beams. Going back and reconnecting yellow wire after trying test light , it seemed to work w/ the original wire again but I'm skeptical.
As far as getting no change at #3 fuse after jumping to bypass of Grey- red and gray -black lengths, what next?
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"A life of peace and happiness depends on your own gratefulness"

[liquidrush]

Probably late for this but I highly recommend that you get yourself a power probe. It's one of the best diagnostic tools you can have for electrical and wiring issues. You can apply power, you can apply ground, you can measure voltage or you can measure resistance. You can. There's plenty of knock offs for probably half the price or better but either way, it's way better than a test light.