Replacement ignition switch has 3 terminals - old one had 4...

[MrMargaretScratcher]

Hi there,

i've got a new ignition switch to replace the old one, but I'm a bit confused as to where this brown wire that was connected to a terminal on the old switch should now go:

It's from the same bundle of wires in the loom as the other 3 wires that go to the ignition.

Potentially related, the indicator and headlight flasher relays seem to not be working correctly since swapping the switch - they will flick on and off rapidly before sticking.

[clymoj]

Brown is usually earth. And unusual flashing and constant on/off instead of flashing can be a sign of earthing problems too.

The body of the light switch earths to the dash, so you can swap the spade connector for a ring connector and link it under the screw that holds the switch to the dash, or you can create a link cable with a male spade to take it to an earthing point elsewhere.

A normal ignition switch should have 3 connections (all live) and all earths should go to the body/chassis somewhere but sounds like maybe the indicator earth on your bus has been routed to the ignition switch rather than to the body.

The indicator flasher was originally a metal unit which screwed to a mounting by the fuse box so was earthed to the body that way. But modern ones are plastic and run an earth cable so there’s no ‘official’ place for the earth cable to run to. So maybe that’s what your extra brown wire is?

Hope that helps, I’m no electrician but I spent last weekend under the dashboard with a multimeter and now have lots of flashy lights so hopefully in the right direction


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[MrMargaretScratcher]

Nice, yeah that would make sense, I'll try temporarily earthing it to see if that works, and the ring connection to earth to the ignition switch screw sounds like a good shout.

[vwJim]

Never seen an ignition switch with four connections. Does it have a part number? VW emblem?

[MrMargaretScratcher]

Never seen an ignition switch with four connections. Does it have a part number? VW emblem?

Nah I think it was aftermarket, god knows where from...


Just tried to earth that brown wire on the underside of the dash, but didn't seem to help. Also, it seems the two black wires that go to 15/54 seems to be heating up when I switch on the ignition, so I'm guessing something is shorting out somewhere?

[clymoj]

Hmm, do you know what number terminals each wire was connected to on the old switch?

Of yours in the photo Id be very surprised if the two reds aren’t 30 and 50. 30 is from the battery through the fuse box and daisy-chained via the headlight switch so you can tell that one as you can trace it straight to the light switch. 50 is straight to the starter so you can tell that one as if you disconnect it your bus won’t start.

Then the two black cables to the same terminal is 15, the thicker one goes to the coil, the indicator relay positive and some other things on later buses (all via the fuse box) and the thinner one goes straight to the idiot lights on the dash. This latter one is important as the indicator dash lights work by receiving two lives which gives zero electrical flow - if one of these lives goes to zero then the lights go on. Often this has been misunderstood and ‘fixed’ with an earth when modern indicator flashers have been fitted.

It could be worth seeing if you can get your indicators working without any of the dash flasher bulb bits connected (particularly the bulb taken out of the pod) and see if that helps? This is often a loose connection anyway so may have been dislodged when you were changing the ignition switch?



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[clymoj]

https://www.thesamba.com/vw/archives/info/wiringt2.php

These are invaluable by the way if you don’t already use them. The ignition is the unassuming little circle labelled D halfway down the diagram.


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[MrMargaretScratcher]

Yep, 50 to starter, and 30 to light switch is what I've got, then the other terminal (Labelled 15/54) is the one with the two black wires as you say. I've also had the engine out so I'm wondering if maybe I've connected the wire to the wrong terminal of the coil. :/

[MrMargaretScratcher]

Yep I had the coil wire going to the wrong terminal

So, no more heating up terminal, but same behaviour on the relays - the headlight flasher will work a few times before stopping, and the indicator relay will rapidly buzz flick/on and off before becoming stuck on.

Also, it seems I have continuity between terminal 15 on the ignition and ground - that's not right, surely?

Not tried disconnecting/removing the bulb from under the dash, I'll give that a go and report back.

[clymoj]

Correct, 15 should be live so no continuity to ground if the ignition is on.

A helpful discovery for me was that the indicator dash lights should be connected to the same relay pin as the indicator stalk which is terminal S on the old diagrams but has a number on modern relays. So if you have a 4-pin relay designed to have a separate pin supplying the dash lights then you ignore that 4th pin.

An alternative way to wire it up is to use the 4th pin to supply the dash light but you would then need to run the other side of the dash bulb to an earth instead.

If you’re caught between the two ways of doing it then you end up with either a buzzing indicator relay or permanently lit dash indicators.


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[MrMargaretScratcher]

Correct, 15 should be live so no continuity to ground if the ignition is on.

This was with the ignition off, but the switch is currently just dangling so in theory there should never be a path to ground from that 15 terminal, right?

I'll dig around again for a bit tomorrow night, cheers!

[MrMargaretScratcher]

Sooo, with ignition on, there's there's no continuity between terminal 15 and ground, so that's good. I removed disconnected the wire from terminal 15 on the switch to the dash lights, same thing.

However, I did give the fuses a bit of a twist to see it that might be the issue, and now my headlight relay is working (although my headlights stay on with the ignition off, but they've always done that...)

I just swapped the realy out of my other bus, and it seems to now be working, albeit flashing very quickly. One of the rear bulbs isn't flashing, but it's fast both sides, even on the side where both front and rear are working... EDIT: Neither of the rear indicators were flashing, just one side was flashing the rear red light, which is what I could see from looking back out of the dirvers door. Now all working correctly it seems!

...and the mystery brown wire is still disconnected

[clymoj]

Well, a happy ending then. Check the rear bulbs and wiring and you’re good to go by the sounds of things.

Don’t forget to tape off that brown wire so it doesn’t short on the dashboard. And then maybe one day you’ll find something not working and try attaching it again!


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