Mystery switch and wire

[furgo]

Cleaning up the wiring has been on my TODO list for quite some time, but I somehow manage only to do it bit by bit. After doing some fixes today, I came across these two items that had me a bit puzzled:

Mystery switch

I need to trace both wires of this two-terminal part, but it seems at least one of them is connected to +12V switched.

As it has only the two terminals, I assume it is a switch of some sort. It has a VW stamped logo, but no part number.

I was hoping someone might recognize it due to its peculiar shape.

Mystery wire

This is part of a PO hack: he used a household mains cable, cut off the ground wire and used the phase and neutral wires to carry signals/power from the engine compartment to the dashboard.

One of the wires connects the ignition coil's (-) terminal to the tach signal at the front. That's sorted

The second one is the one I can't quite understand: it connects the ignition coil's (+) terminal to what would appear to be the ignition switch at the front.

Looking at the pictures, it connects the blue wire from the coil's #15 terminal (+) to a red/black wire and ultimately to a gray/black cable that goes from the fuse box through the steering column mini-harness to the ignition switch.

And looking at the wiring diagrams on track 10, it seems to be a way of repurposing the original wire for the ignition key warning buzzer relay (now gone).

But I have no clue what the purpose of connecting the ignition switch Su terminal to the coil's #15 terminal is.

Any ideas?
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'79 Westy, P22 interior, FI 2.0 l Federal, GE engine (hydraulic lifters)

Decode your M-Plate

[busdaddy]

It's an early splitbus wiper switch, what your PO had in mind is only something they can answer, security system perhaps?
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[telford dorr]

Looks like the same switch used for the rear interior light in a bus. I've used them to operate an aftermarket fog light relay, wired between headlight switch terminal #58 (tail lights) and the relay coil, so the fog lights only operate when the headlight switch is not off.

If the wire from the ignition switch is gray, it's likely an aftermarket switch. The gray wire is 'hot' when the key is in the 'off' position. Not terribly useful in a bus - unsolder or cut it off at the switch.
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'71 panel, now with FI
'Experience' is the ability to recognize a mistake when you're making it again - Franklin P. Jones
In theory, theory works in practice; in practice, it doesn't - William T. Harbaugh
When you're dead, you don't know you're dead. The pain is only felt by others.
Same thing happens when you're stupid. - Philippe Geluck
More VW electrical at http://telforddorr.com/ (available 9am to 9pm PST)

[furgo]

Mystery switch

[Wildthings]

The factory uses a black wire for the #15 ignition circuit and it looks like the PO removed one end of the #15 wire from the ignition switch to the fuse box from the box and attached it to your mystery switch and then ran a wire from the other side of the switch on to the fuse box. This would act as a kill switch preventing the engine from running when in the "OFF" position.

If the terminals on that switch make contact with a ground, you are going to smoke your ignition switch so assuming you keep it, I would recommend adding heat shrink over the wire ends and maybe adding other non conductive physical protection for the switch.

[Mal evolent]

green is the traditional color of a tach wire. when I see extra wires and hidden switches going back my first suspicion would be a fuel pump cutoff.
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[furgo]

I had some more fun tracing today, and indeed I can confirm the mystery switch is a kill switch. However, the mystery wire keeps puzzling me.

Here's what I saw: mystery wire comes from #15 (+) and ends up in the front as a GY/BK wire into the ignition switch. In fact, that GY/BK wire was originally the door buzzer signal (Su), but the PO removed the terminal from the ignition switch and recrimped it together with the #15 (+) terminal. You can see it in this picture:

The weird thing is, that relocated wire seems to be a bypass for the kill switch. With it, the kill switch has no effect, as the bypass closes the #15 power signal circuit. Like this:

I don't quite get why getting the trouble of installing a kill switch and then going the extra trouble of creating a bypass (even recrimping the ignition switch) and rendering it useless.
_________________
'79 Westy, P22 interior, FI 2.0 l Federal, GE engine (hydraulic lifters)

Decode your M-Plate

[Mal evolent]

[Wildthings]

Previous owner X installed kill switch and then goes through some kind of life trauma (divorce, job loss, illness, etc) and disappears from the scene. His wife or heirs then sell the his van as a non runner because it will not start.

Previous owner X+1 buys the non runner and jury rigs power to the ignition so that the bus will run. He fails to figure out that he also needs power to other items on the #15 circuit so the alternator never works nor several other systems, so he sell the van to another owner.

Eventually you become owner X+1+1+1...+1 and begin to try to figure out how the wiring ever got so screwed up.

[furgo]

And here I am, striving to become a better +1...
_________________
'79 Westy, P22 interior, FI 2.0 l Federal, GE engine (hydraulic lifters)

Decode your M-Plate

[telford dorr]

How about: owner cobbs in a kill switch, not realizing that the switch chosen can't handle the load (because it's designed to run a dome light). Switch predictably fails. New owner doesn't want to bother to figure out the mess, so he cobbs in a bypass wire, using small scraps of whatever wire is laying around. and a dozen random butt splices, and it (sort of) works. Job done. You buy it, and wonder WTF's going on. And here we are...
_________________
'71 panel, now with FI
'Experience' is the ability to recognize a mistake when you're making it again - Franklin P. Jones
In theory, theory works in practice; in practice, it doesn't - William T. Harbaugh
When you're dead, you don't know you're dead. The pain is only felt by others.
Same thing happens when you're stupid. - Philippe Geluck
More VW electrical at http://telforddorr.com/ (available 9am to 9pm PST)

[furgo]

Good points, thanks.

I'll remove the bypass in any case, but I'm considering leaving the kill switch in for now. At some point I might replace it with either a switch of a known power rating or just remove it altogether. I'm not too convinced how effective it is as an anti-theft device if it can be found just behind the fuse box.

In any case, I've been trying to find out more about the rating of that split bus switch I've got.

Unfortunately, there is no part number or manufacturer markings on the switch itself to find out its power rating. Perhaps a good guess is to look at the wiring diagrams of a split bus where it was used. Following the switch line to the fuse box, it is protected by an 8 A fuse. So if I'm not mistaken, it should hold that current, even if for a short time.

However, the #15 track that the switch is interrupting is effectively unfused. While its branches do have fuses, that main trunk goes from the ignition switch to the ignition coil directly. The wire is 2.5 mm², which looking at specs should hold roughly 22 A @ 30°C.

In summary, I think the switch is not designed to hold the worst-case current through the line it's on. It's still functioning and I think it would work in most cases... until it fails. So if I were to keep it, I'd probably have to shop for a beefier one. Yet I'm not convinced by the usefulness of kill switches.

Long story short, I think I'll remove it and bridge the #15 line back together. Thanks for helping me collect my thoughts and bring the wiring closer to stock
_________________
'79 Westy, P22 interior, FI 2.0 l Federal, GE engine (hydraulic lifters)

Decode your M-Plate