Coil wire shriveled near fuse block.

[Frodge]

Well, while changing my tie rod end, which went really smoothly, I peeked under the trunk and saw a burn hole in the center of my carpet. Weirdly the two sets of wires that run from the front right headlight area in those two rubber conduits look fine. So I kept peeking around. Then I saw the shriveled hot wire to the coil, which splits to the speedometer? For what? It looks like before my ownership someone put a blue butt connector in there for some reason. Not sure. I don’t even know how long this has been like this. Could be a long time. Everything still works. So I have a bunch of questions. What would cause that burn mark in the carpet? It very possibly could be from floor pan work from a couple years ago and it just got hot underneath? Those wires that run in the two conduits look fine.

Now for the hot wire. What caused this to shrivel up to where it goes down in the conduit near the windshield? How do I fix this? What will I need? Number, I was getting ready for a show this weekend. Still works but would like to repair it.

[raydog]

What year Bug is this? Usually when a wire is shorted, the hottest point is at the short to ground or the overload. I would start with the terminal in your hand. Is that the one the goes to the fuse panel? What connection to the speedometer did the other end go to? Something doesn't sound right. But definitely repair/replace that wire

[Frodge]

1970

The shorter terminal closer to my hand goes to the fuse block, the longer one that pigtails off that went to the lowest spade connector on the speedo. It got shriveled at some point all the way to under the windshield on the drivers side about 2 inches before it goes down . I have no idea how to do this or where it goes. It connects to the right most spade connector on the fuse block closest to the windshield when looking into the trunk from the front.

[Cusser]

Oooooh - the un-fused wire from the "hot" side of the fuse block back to the coil positive terminal #15 shorted out, melting the insulation on that wire.

Run a brand-new wire back to the coil positive terminal, and consider adding an inline fuse like I did.

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1970 VW (owned since 1972) and 1971 VW Convertible (owned since 1976), second owner of each. The '71 now has the 1835 engine, swapped from the '70. Second owner of each. 1988 Mazda B2200 truck, 1998 Frontier, 2014 Yukon, 2004 Frontier King Cab. All manual transmission except for the Yukon. http://www.thesamba.com/vw/forum/album_page.php?pic_id=335294 http://www.thesamba.com/vw/forum/album_page.php?pic_id=335297

[Frodge]

What causes this? How do I run in factory next to the harness?

[Luft kühl]

This is usually caused by a short circuit at the wire that is connected from the coil to the choke and idle cutoff solenoid on the carburetor.

Unfortunately, your ignition switch has probably been toasted as well.

[Frodge]

[Frodge]

[Frodge]

Anyone ?

[raydog]

The part of the wire that connects to the speedo is 12v+ to the gen, oil, and turn signal bulbs. The only way to be 100% sure would be replace the entire wire. If you go with splicing, I would first disconnect at the coil and check for any resistance on the remaining undamaged wire with ohmmeter from that wire to grd. If that is OK then splice, solder your splice then heat shrink over repair.

[Frodge]

I have an ohmeter. How would I measure for resistance? Never did that before because I never had this problem.
Where would I run a new wire? What gauge?

[volksworld]

it all depends on how "correctly" you want to repair it....due to some law of physics or other when you ground out a hot lead it gets hottest at both ends and burns towards the middle....so depending on how long it was shorted out determines how much of the insulation is burnt ....now since its bundled together with all the other wires in the harness its now melted to them and if it got hot enough it cut through their insulation too and may be a couple thousandths away from shorting them out...and as what is left to the fried insulation will get more brittle with age contact is inevitable....so just abandoning the original hot lead and replacing it isnt necessarily the answer as it could still cross 2 or more other wires together even if it isnt hot...unless the fried wire is really corroded an ohmeter wont tell you anything as a wire with all the insulation burnt off will show no difference in resistance than a good one....at the very least you need to cut open the harness cover on the A pillar , down the rocker, and behind the rear "door" panel and see how far its fried...if its just the last foot or 2 you could splice in a new piece and tape up damage to the other wires ....otherwise you'll be a lot better off in the long run to replace the harness

[Cusser]

This happened a long time ago.

Since your issue seems confined to a short region which is accessible, and you know how to solder, I think I'd just solder in a length of heavier-gauge wire and use heat shrink wrap over the new solder joints. Make sure to let the solder cool normally without jarring it, makes a stronger joint. And do away with that butt connector while you have the solder stuff out anyway.

Alternative is to run a brand-new wire from the front back to the rear like I have done. When I resurrected my 1970 I actually used the now-unused AC compressor wire as the coil wire because that was already there !

Either way, go to the parts store and buy an in-line fuse (use a fuse of at least 10 amps) and add that to the wire right at that fuse box connection. I used a male and a female crimp connectors on mine so that I could just plug it in, but you could simply solder this in (get insulated crimp connectors if you can). Also, you can use an in-line fuse with a modern type fuse, doesn't need to be a cylindrical type fuse or VW fuse. And buy some extra fuses for that, keep in the VW, maybe the ash tray. Use shrink wrap or electrical tape on those connections too.

_________________
1970 VW (owned since 1972) and 1971 VW Convertible (owned since 1976), second owner of each. The '71 now has the 1835 engine, swapped from the '70. Second owner of each. 1988 Mazda B2200 truck, 1998 Frontier, 2014 Yukon, 2004 Frontier King Cab. All manual transmission except for the Yukon. http://www.thesamba.com/vw/forum/album_page.php?pic_id=335294 http://www.thesamba.com/vw/forum/album_page.php?pic_id=335297

[baldessariclan]

To me, it looks like the fried section of wiring is the one that goes between the ignition switch and the fuse block. Per the Bentley wiring diagram for 1970 model year ( https://www.thesamba.com/vw/archives/info/wiring/1970_VW_Type_1_Poster.jpg ), this section is smaller gauge (1.5 mm^2) than the separate section that runs from the fuse block back to the coil and etc. in engine compartment (2.5 mm^2).

So seems possible that that long run to the back may not have gotten as hot as the section that got fried in the trunk, and will still be ok. I'd say if that section looks good/intact at both ends (portion up in trunk attached to fuse block, and portion in rear running to the coil & etc.), it's likely ok in the middle as well.

If that section running to the back looks good, then all you probably need to replace is the section in the trunk that runs from the fuse block to the ignition switch. Ref. the wiring diagram for connection points and wire gauges to use (just convert the mm^2 values to equivalent or better AWG values).

I'd also recommend installing an inline fuse into that replaced section of wiring, as Cusser noted above. I did similar in my car -- cheap insurance against this type of damage in the future from potential shorts back at the coil or carb wiring connection points.
_________________
1971 Standard Beetle — fairly stock / driver

baldessariclan -- often in error, never in doubt...

[Frodge]

Where does the long section go into the block vs the ignition?

[baldessariclan]

The wiring diagram ( https://www.thesamba.com/vw/archives/info/wiring/1970_VW_Type_1_Poster.jpg ) shows the "long section" (going to back of the car) as black 2.5 mm^2 wiring, attached to the fuse block right next to where the "short section" (black 1.5 mm^2 wire, running to ignition switch) connects. My car is wired similarly, and looks like what the wiring diagram for your model year shows.
_________________
1971 Standard Beetle — fairly stock / driver

baldessariclan -- often in error, never in doubt...

[Frodge]

I’m confused. The burnt wire has two terminals on the end. When looking into the trunk, the one of those terminals go to the rear, right most spade connector. The other that pigtails off of it goes to the lowest spade connector in the speedo. Where does the ignition switch wire terminate in the fuse block?

[baldessariclan]

That burnt section of wiring is the "ignition switch wire", and connects to the fuse block just as you've noted. The other end of it (running up towards dash) connects to the ignition switch.

When you turn the ignition switch "on" (or to the "run" position), power from the battery is free to flow through that wire to the fuse block, and from there to the different wires that connect to that same section of the fuse block (i.e. the left-most 4 connection points on the fuse block, 2 in front which are fuse-protected, and 2 in rear which are not protected). Make sense?
_________________
1971 Standard Beetle — fairly stock / driver

baldessariclan -- often in error, never in doubt...

[Frodge]

Ok. So where does the wire to the coil go on the fuse box?

[baldessariclan]