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Tue Jul 30, 2019 3:46 am

Do you think us bug owners should fuse the hot wire going to the coil from the ignition? Thoughts from both sides are appreciated.

Tue Jul 30, 2019 4:08 am

From electricians sight no circuit should be unfused. Easy as it is.
But there would still be a risk left on the cables that run to/from the battery unfused.

One can argue about whether VW went for cost savings or reliability, when they left the ignition unfused.

On modern VWs there is no cable leaving the battery unfused except starter motor and alternator.
In contrast to that there are cars (from some strange manufacturers) where even a blocked wiper motor (due to ice or accident) will cause a cable fire.

Regarding the old VWs in my eyes the highest risk is caused by the cables in the engine bay where the engine heat (and oil and fuel vapor) hardened the insulation over 50 years.

Tue Jul 30, 2019 4:53 am

How does hardened insulation cause a fire?

Tue Jul 30, 2019 5:00 am

Frodge wrote: How does hardened insulation cause a fire? It will crack and eventually fall apart. Any crack is a potential short that can possibly cause a fire. Obviously it's not a sure thing but mix in the fact that these cars are so old now, and many have had very sub par maintenance to downright hack repairs that it all adds up to future problems.

Tue Jul 30, 2019 5:44 am

There is no debate. Any power [+] wire should be fused. Otherwise, eventually it will fry the wire.

A (very brief) selection of examples of what happens when the ignition wire shorts:
https://www.thesamba.com/vw/forum/viewtopic.php?t=499639&highlight=ignition+wire
https://www.thesamba.com/vw/forum/viewtopic.php?t=532358&highlight=ignition+wire
https://www.thesamba.com/vw/forum/viewtopic.php?t=720047&highlight=ignition+wire
https://www.thesamba.com/vw/forum/viewtopic.php?t=675634&highlight=ignition+wire
https://www.thesamba.com/vw/forum/viewtopic.php?t=541605&highlight=ignition+wire
https://www.thesamba.com/vw/forum/viewtopic.php?t=720962&highlight=fuse+ignition

Fuse the wire.

Tue Jul 30, 2019 6:21 am

TK-CS wrote: One can argue about whether VW went for cost savings or reliability, when they left the ignition unfused.
I'm certain cost savings had a part to play, but there was probably additional factors being considered as well.

I vote to add an in-line fuse at the fuse box end. Just disconnect the black wire that connects to the INPUT side of the #15 fuses that runs to the rear of the car (there are often two black wires in the main harness but only one comes from the fuse box). Insert a 10A or 15A fuse between the fuse box and the wire. That will protect the entire wire segment and all the engine compartment electricals powered by this wire.

IMHO, you should also add a fuse (or circuit breaker) into the B+/#30 wire coming off the battery (the smaller wire, NOT the positive cable to the starter solenoid) to the VR or the white rectangular junction under the rear seat. It will need to be a BIG one. I think I used a 60A fuse from a car stereo amplifier? I've seen others use a 100A circuit breaker here that can be reset.
This fuse is for those "oh sh!%#!!!" times when you REALLY screw up.

If you do a lot of electrical work on your car, a battery cutoff switch is a worthwhile investment. I find most instances of shorting out wires is because people are too lazy to disconnect the battery before they start working on wiring (myself included). Adding a cutoff switch makes it easier to do... especially if you can flip the switch w/o having to lift the rear seat.

Tue Jul 30, 2019 6:33 am

Fuse it and add a relay.

Tue Jul 30, 2019 9:12 am

ashman40 wrote: This fuse is for those "oh sh!%#!!!" times when you REALLY screw up.

That's hilarious.

I add a quick disconnect to my batteries as well.

Tue Jul 30, 2019 10:32 am

Quote

"I'm certain cost savings had a part to play, but there was probably additional factors being considered as well."

I seem to remember from my BMW owning days that throughout the 1980's BMW did not fuse the power feed to the coil be it K Jetronic, L Jetronic or DME.
So you could do some serious damage to the wiring loom if you earthed a live coil feed.

I doubt they would have put a coil feed without a fusable link in it for economy reasons.

Tue Jul 30, 2019 10:46 am

I'm still have mine unfused. I protect the ends of the ignition wire. Over decades I've never had a problem.

A fuse blowing or making a bad connection while passing a semi on a two lane road with oncoming traffic is real but remote. As I've said before, my brother has his fused and the fuse has failed a couple of times but in safe locations.

If I were to fuse my ignition wire, I'd solder a slightly larger fuse into the circuit and not rely on a fuse holder. Of course, the fuse could still blow.

Metal contacting and grounding the + coil, anti-dieseling solenoid or choke is what would most likely melt the wire or blow a fuse. So, protect the ends of the ignition wire no matter what you decide.

Tue Jul 30, 2019 11:03 am

I would just put a terminal cover on the ignition power feed so that earthing it is not possible.
The less going on behind the dashboard the better. People are always complaining how the previous owner messed around with wiring. One less problem to worry about.

Seriously if the insulation is cracked from age and heat, which most would be now, it needs replacing. Once fixed the problem goes away.

And don't use an insulated crimp for the repair because you have no visable idea of the crimp integrity.

Tue Jul 30, 2019 11:45 am

I added such inline fuse on my 1970 and 1971, after each "lost" its factory wire.

Tue Jul 30, 2019 6:24 pm

I fused the ignition circuit on my '70 a few years ago. Haven't done the wire going to the voltage regulator, however. Thanks for the reminder, Ashman. Wouldn't mind being pointed to a good fuse suggestion for that...

Tue Jul 30, 2019 6:40 pm

I almost burnt mine up about 2 months ago after the positive timing light cable touched ground. It definitely should be fused. It's so easy there's no excuse not to. The car shut off, and i didn't know why. Until i saw smoke.

Wed Jul 31, 2019 2:07 am

I fused my coil from the fusebox in my '73 bus. It kept on MELTING fuses, without popping them. But there was a lot of weird stuff going on there, I just came to think it was fusing the engine+, but maybe not. All i know is that since I changed it back to stock, all is well.

Wed Jul 31, 2019 8:30 am

Cusser wrote: I added such inline fuse on my 1970 and 1971, after each "lost" its factory wire.

I have not blown either of these added inline fuses, quite a few years on my 1971, and two years on my 1970.

Wed Jul 31, 2019 8:47 am

There are good arguments pro and con on this issue. Thus I am still confused.

Bug On!

Wed Jul 31, 2019 9:37 am

AlmostHeavenWV_VW wrote:
Fuse the wire.

Lol, that's actually the inline fuse from my '72 Super. I had an issue where I kept blowing it, never quite figured out why, although I think it may have had to do with the VDO gauges drawing power from the same position. That's a 10-amp fuse, but reading one of Ashman's posts made me think I should have gone w/a 20-25.