Auto electrics -- what a PITA!

[xwhatsit]

Discovered something weird as I pulled up outside my garage tonight -- no tail-light. Pulled out light bulb, both filaments are fine; brake light still works as well. I go to get my multimeter and find, of course, that it's out of batteries -- what's more it's a cheap one that you can't plug into the wall. Bitch!

Anyway, with the bulb out, I tried running a spare indicator unit off the outputs. The brake light lights the indicator; the tail light has nothing.

Following the maze of wiring diagram I discovered that the parking light and tail light are linked, so I tested out the parking lamp on the `P' setting of the headlight switch. Nothing at either end. Interestingly though, the parking lamp and tail-light work when the `P' setting of the ignition barrel is used. This let me work out which sections of wiring must work for sure and which must be suspect. I've included an attachment.

So that's all very well that I know what wiring is under suspicion on the wiring diagram, the problem is working out where the hell it is on the bike. Rusty connectors, wiring zig-zagging across to both ends of the bike and back, wiring under the fuel tank, into the headlight shell...

If this was a circuit board I'd have it traced and re-soldered in five minutes.

What sort of things normally fail in the wiring I have shown? Connectors, switchblocks, that sort of thing?

[tri boy]

All, and everything can fail. If your handy with circuit diagrams, then I would suggest using a sharp circuit tester probe,...and start probing.

[xwhatsit]

Well I'll go and get a battery for my flaming multimeter tomorrow. Pulled the old one out, it looks like the type of prick you can't find anywhere, so I may just buy a whole new ultra-cheap multimeter for the purpose of just continuity testing. They have them for $10 these days, mad.

I have a 5V logic probe, but I don't think that'll help me much.

[tri boy]

repco do a nice brass bodied 12-24v probe for about $20.
Better than the cheap plastic ones, and has a fine point that doesn't damage wiring as much.
plus you can go up to truckies if you like, and ask if any one need probing.

[xwhatsit]

repco do a nice brass bodied 12-24v probe for about $20.
Better than the cheap plastic ones, and has a fine point that doesn't damage wiring as much.
plus you can go up to truckies if you like, and ask if any one need probing.

How does that work? One end attach to ground, the other just reads positive voltage? Just like a logic probe? I come from the land of ones and zeroes, it's not often I fool around with this stuff.

See I'm not running a battery in the bike either, I might have to charge my one up.

[tri boy]

Yep, just probes voltage. wire end has alligator clip for earth, and theres a bulb in line for the probe.
You get used to the brightness difference in the bulb if your doing 12 and 24v.
Only down side is it can't "read" a voltage drop in analogue or digital display like a meter. But for quick loom checks, they are great.
The Rs series did prefer a battery in the circuit, but if you haven't damaged the Reg/rectifier yet, then I guess its OK.

[xwhatsit]

Oho I was just worried about pissing off my neighbours by leaving the thing idling for 20 minutes while I do the probing about

Cheers for the help.

There's a flaming big capacitor in place of the battery to smooth out the spikes, and I'm thinking it should provide enough load to keep the reg/rec happy. If the reg dies I have a nice switching mode regulator circuit all laid out and ready to order from the PCB place, so I'll just solder up one of those bastards and that should cure it for all time.

The engine is the XR250 lump which didn't run any battery of course -- and I've seen plenty of Japanese flat-tracker/custom CB250RS with no battery, so I'm hoping it'll hang together. Be interesting to find out what the cause of my tail-light issue is, whether it's a melted wire or something nasty.

I just went back and looked at the bulb -- Haynes manual says I want a 5W/21W tail-light, there's an 8W/23W in there. Interesting, but I don't think there's enough difference to melt stuff.

[davereid]

Loom usually fails where it twists - near the steering head. You may find your tail light works at some steering angles.

[imdying]

See I'm not running a battery in the bike either, I might have to charge my one up.

If you don't start the bike or use the headlights (unplug them if there's no swithc), then you're only going to draw a low current, so you could attach your battery charger to the battery leads instead.

[xwhatsit]

Phwoar, fixed, hopefully.

Got a new battery for the multimeter and got to work. Traced it all the way up until it disappeared into the headlight, pulled that to bits -- and it popped out into the ignition barrel.

Unplugged the ignition barrel `sub-loom', and started fiddling around with that. It seemed that (if you look on the original attachment) that the TL1 wire up to the connector was faulty -- sometimes it conducted between TL1 and TL2, sometimes if you bent the wiring it didn't. However I discovered it also wasn't conducting at the actual terminal coming out of the ignition barrel -- scratched my head for a while until I realised that when you move the wiring around, it is tugging/pushing on the terminals on the ignition barrel itself. Poked around some more with the multimeter until I was satisfied with this explanation.

I didn't really want to pop the ignition barrel open -- meant I'd have to de-solder all the wires, and I don't know if I'd ever get the thing back together again. So in the end I did a bit of a kludge -- I cut the TL1 and TL2 just a few centimetres out of the connector block, and soldered them together permanently. If I had a crimping tool I would've just looped a wire around, but this is nearly as good.

As far as I can work out, this won't have any side-effects, please correct me if I'm wrong, though. The only situation that might be possibly weird is when you turn the ignition barrel to `P' -- however I don't have a battery, and `P' switches the engine off, so nothing's going to happen anyway.

Weird system. I can't quite see the point of switching the tail-light twice, once through the light switch and once through the ignition barrel. I'm sure they had their reasons, but I don't see why it's necessary. Oh well. Done now

I may at some point get a new ignition barrel from Econohonda. It would be nice to have a key that matched my tank, so I don't need the two keys, but I don't know how possible that would be to organise.

Thanks for your help, guys. Imdying -- the charger worked perfectly, without carbon monoxide fumes killing me in the garage (too cold to have it open!).

[bimotabob]

Hi

The battery positive goes to the ignition switch then out to the ancillaries.
Unlike many cars the lights always will not work without the key on.
The exception is the "p" position will powers the lights only and this is why motorcycles often have the licence plate light and dash lights wired apart from the head lamp and tail lamp to allow them isolation when in the "p" position.

I have met many people who would just run a "bypass" if something didn't work.

Good to hear you fixed the drama.

I had a good ole CB250RS way back when I was 16 and naive.
The previous owner said: "don't worry about the cam chain noise - it's normal"
Soon oil started pissing out the big hole forming in the barrell where the chain was now visible. Cost me $150 to fix.

Cheers

[xwhatsit]

Hi

The battery positive goes to the ignition switch then out to the ancillaries.
Unlike many cars the lights always will not work without the key on.
The exception is the "p" position will powers the lights only and this is why motorcycles often have the licence plate light and dash lights wired apart from the head lamp and tail lamp to allow them isolation when in the "p" position.

I have met many people who would just run a "bypass" if something didn't work.

Good to hear you fixed the drama.

I had a good ole CB250RS way back when I was 16 and naive.
The previous owner said: "don't worry about the cam chain noise - it's normal"
Soon oil started pissing out the big hole forming in the barrell where the chain was now visible. Cost me $150 to fix.

Cheers

Hahaha yeah, I've had my fair share of top end problems. Top end's still a touch rattly with the so-called cam `bearings' a little the worse for wear.

Yes I suppose the `P' position of the ignition switch is why they run a separate route, although I can think of easier ways of doing it, with less wires running through almost every point on the bike. I'm actually at a loss for when you'd use the `P' position on ignition switch -- you can do the same thing by leaving the ignition on and setting the headlight switch to `P', but I suppose there's a reason for having the redundant method.

At any rate, all I've done is turn a connection from being only on with the ignition, to always on, and as it's routed through the ignition switch indirectly again, it's effectively off when the ignition is off regardless.

I think one day, like there is with the Triumphs and BSAs today, there'll be a huge market for replacement regulators/alternators/complete wiring looms to introduce the old Jap bikes to modern electrical technology.