1979 T140E Electrical Help - Triumph Forum: Triumph Rat Motorcycle Forums
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post #1 of 28 (permalink) Old 06-20-2019, 01:52 PM Thread Starter
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1979 T140E Electrical Help

I have an electrical issue that I hope someone can help me with. The bike starts and runs normal when the key is in the first on position, but if it is in the second on position (all the way to the right for lights on), it shuts down when I turn the handle bars. If I fiddle with wire cluster going into the ignition switch box, then it will correct itself temporarily.

I have checked the connections on the ignition switch and they are fine. Im now assuming that there is a short in one of the wires going into the back of the ignition switch.

Sooo me not being an electrical guy, how do I troubleshoot this and why does it not happen in the first key position? Id love to be able to ride my bike at night this summer
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post #2 of 28 (permalink) Old 06-20-2019, 02:48 PM
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Sounds like a possible broken cable near the instrument binnacle?
They can suffer a bit over time as the bars turn and get trapped.

You could buy a continuity tester that (ideally) has audio and using the wiring diagram trace the end of the wire, get continuity, and then wiggle the wire at the binnacle end until the audio goes.
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post #3 of 28 (permalink) Old 06-20-2019, 03:59 PM
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Hi Eo1bart
A little more information might help diagnosis.

With the key in the second position, when the bike cuts out, do the lights stay on or do they go out?
Headlamp?
Talilamp?
Oil/neutral indication lamps?
Indicators?

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Last edited by Rancidpegwoman; 06-20-2019 at 04:11 PM.
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post #4 of 28 (permalink) Old 06-20-2019, 04:31 PM Thread Starter
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Peg,
The bike totally dies, including all lights
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post #5 of 28 (permalink) Old 06-20-2019, 06:00 PM
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Hi Eobart,
I can think of three or four scenarios in this case.

1) Failure of the ignition switch in the second position. Position 1 clockwise -connects terminals 1 and 2, position 2 clockwise connects terminals 1-2-3-4 putting the voltage out on different wires, the only common path is through the switch.

2) A poor connection in the line between the battery and the ignition switch, allowing enough current to flow when under light load, but breaking down under heavy load (lights on).

3) A poor connection on the other side of the battery (frame/Black wires/battery negative terminal), allowing enough current to flow when under light load, but breaking down under heavy load (lights on).

4) A battery that is faulty and breaking down under heavy load.

In scenario 2, the original glass fuses/holders can give unreliable connections.

To ckeck if it is more likely a connection or the switch.
Remove the headlamp and tailamp bulb, place the ignition switch in position 2 clockwise and see if the bike runs ok without load, but with the switch in position 2 clockwise.

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Peg

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post #6 of 28 (permalink) Old 06-20-2019, 07:46 PM
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Lightbulb

Hi,

This has a few more possibilities than might be obvious at first ...

Firstly, a US bike shouldn't "start and run normal when the key is in the first on position" ... From 1st January 1978, it was a Federal requirement that bikes had lights on in daylight; '79-on, the White wire from the handlebar kill switch was plugged into the Blue/Yellow wires' bullet snap connector inside the headlamp shell, Blue/Yellow is from the headlamp dipswitch on the left handlebar, only energised when the key is in the second "'on' position ... so, when the kill switch wire is connected to them, the key should have to be turned to the "second 'on' position" to energise both ignition and lights.

The connection from ignition switch (terminal #1) to battery positive is the Brown/Blue wire. Amplifying Peg's advice:-

. inspect the fuse and wire terminals very closely and eliminate any hint of corrosion;

. if you have a spare 'known-good' fuse, replace the one in the holder; particularly the tubular glass fuses, the fusible strip can break away from one end cap but, because it's still attached to the other end cap, the broken end can make intermittent contact with the cap;

. with ignition and lights on, without turning the 'bars, grab the wiring between key switch binnacle, headlamp shell and the rest of the bike and pull it around; if that causes everything electrical to "die", likely a broken wire.

Quote:
Originally Posted by eo1bart View Post
assuming that there is a short in one of the wires
Uh-uh; a "short" is a short-circuit - blows the fuse or melts wires.

Hth.

Regards,
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post #7 of 28 (permalink) Old 06-21-2019, 07:21 AM Thread Starter
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[QUOTE=StuartMac;2003953352]Hi,


. with ignition and lights on, without turning the 'bars, grab the wiring between key switch binnacle, headlamp shell and the rest of the bike and pull it around; if that causes everything electrical to "die", likely a broken wire.

Stuart,
If I fiddle with the wires going into the ignition switch box , everything "dies" like you said, but only if I have the key all the way to the right.

Question: Do all the wires from the ignition switch go through the headlamp shell before continuing to their final connection? That sure would make it easier to find the damaged wire.
Thanks
Bob
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post #8 of 28 (permalink) Old 06-21-2019, 02:32 PM
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Hi Bob,

Quote:
Originally Posted by eo1bart View Post
Do all the wires from the ignition switch go through the headlamp shell before continuing to their final connection?
Certainly White, Brown/Green and Blue wires do, because the 'next' switch in most circuits is on the handlebars, Brown/Green certainly originally connected to the pilot lamp in the headlamp reflector.

The only wire that might not is the Brown/Blue to the fuse and battery positive - if you can see it inside the headlamp shell, it does.

Quote:
Originally Posted by StuartMac View Post
. with ignition and lights on, without turning the 'bars, grab the wiring between key switch binnacle, headlamp shell and the rest of the bike and pull it around; if that causes everything electrical to "die", likely a broken wire.
Re-reading my earlier post, I realise I could've explained another part better - because your bike does "start and run normal when the key is in the first on position", a PO has fiddled with original connections inside the headlamp shell. Ime, in addition to the other checks Peg and I suggested above, you should check the connections inside the headlamp shell to ensure the problem you're experiencing isn't simply a loose and/or corroded connection ...

I appreciate you might not relish the latter suggestion, especially as you posted earlier, "me not being an electrical guy"; however, because Lucas and the Co-op didn't make it difficult for themselves to comply with the US requirement, if I tell you what the PO should have done, you can see whether he did do it ... or something else ...

As I say, originally on '79-on US-market bikes, the White wire from the handlebar kill switch was connected inside the headlamp shell to the Blue/Yellow wires bullet snap connector, so the bikes should only "start and run normal" with lights on, when the key is in the second on position.

However, Lucas normally designed wiring harness that only required same-coloured wires to be connected together. On non-US-market bikes, the White wire from the handlebar kill switch is instead simply connected to other White wires inside the headlamp shell (originally, there were two '4-way' (two wires in each end) snap connectors for all the White wires). That's all the PO should have done so the bike "starts and runs normal when the key is in the first on position".

Hth.

Regards,

Stuart
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post #9 of 28 (permalink) Old 06-21-2019, 03:56 PM Thread Starter
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Lot's of good info. I'll print this thread and the schematic and have at it tomorrow and then report back.
Regarding the lights on, I believe the California bikes (and maybe a few other states) were the ones wired for lights on all the time. I live in Massachusetts and it is recommended to put your lights on in the daytime, but it is not required by law.

Thanks to all for the help!
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post #10 of 28 (permalink) Old 06-22-2019, 02:45 AM
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Hi Bob,

Quote:
Originally Posted by eo1bart View Post
Regarding the lights on, I believe the California bikes (and maybe a few other states) were the ones wired for lights on all the time. I live in Massachusetts and it is recommended to put your lights on in the daytime, but it is not required by law.
Interesting. I struggle sometimes with the difference between English and Scots laws but at least the road traffic ones are the same.

My understanding was lights-on was a FMVSS for all vehicles built after 1st January 1978? This was the one that also included tougher emissions, for which Meriden had to build the interim US-only '78 T140E which had the parallel-port cylinder head and Mk.2 Concentrics but not the electronic ignition; the '78 T140E also had a different headlamp toggle switch, that could be wired to have pilot and tail lamps on all the time.

I assumed - wrongly? - that a FMVSS would apply to all states? Or, as can happen here with EU laws and regulations, individual states can apply for a derogation?

If Massachusetts doesn't have a lights-on requirement and the bike was sold new there, possibly it was the original dealer that changed the kill switch wiring connection?

Regards,

Stuart
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