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Discussion Starter #1
Hi Guys, I am coming to the end of a total rebuild of a 1966 TR6 and have encountered an electrical fault that has baffled me for the past 2 weeks.
When I turn the ignition switch on, lighting switch is off, the rear light comes on together with the speedo and rev counter lights.
I have gone over the wiring diagram so many times but cannot find the problem.

Your thoughts and suggestions would be much appreciated, cheers.

Pilonpete
 

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Hi Pete(?),

Firstly, welcome to the Forum. :)

coming to the end of a total rebuild of a 1966 TR6
turn the ignition switch on, lighting switch is off, the rear light comes on together with the speedo and rev counter lights.
I have gone over the wiring diagram so many times but cannot find the problem.
'UK & General Export' TR6 or US-market TR6R or TR6C? 564 rear lamp on a black numberplate or 679 lamp on a polished ally casting? 88SA rotary lighting switch or later toggle switch? If later toggle switch, which 5-figure number and are you sure you've connected wires to terminals correctly?

You probably need to look at the wiring on the bike itself, rather than the diagram:-

. Bad rear lamp "earth"? As standard, your bike's rear lamp had only the wires to tail (Brown/Green) and brake (plain Brown); return is supposed to be through random metal-to-metal contact between bits of bike. As you might guess, the latter doesn't work well after 54 years, total rebuild or not (if the total rebuild includes a high-quality repaint, high-quality paint is a crap electrical conductor :rolleyes:). Ime, do the following anyway; even if it doesn't fix the immediate problem, the rear lamp electrics will be more robust long-term:-

.. run a Red wire alongside the Brown and Brown/Green wires to the rear lamp; connect one end of the Red wire to existing Red wires under the seat;

.. either thread the other end of the Red wire into the rear lamp with the other two and solder the bared end to the outside of the bulb holder; if threading isn't possible, choose a rear lamp fastener with electrical continuity to the lamp, terminate the new Red wire with a ring terminal that'll fit the chosen fastener and attach. (y)

. Rear lamp tail filament, speedo. 'n' tacho. lamps should be connected together by Brown/Green wires. Otoh, ignition switch on, lighting switch off, only White wires and connections should be energised. So the two wire colour combos. are connected together somewhere?

. White wires connect to the rear lamp brake filament through any brake switch and the Brown wires; you haven't connected the wires incorrectly in the rear lamp?

Hth.

Regards,
 

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If it is home market TR6 and not the export TR6R feel free to post some pics. I think I've only seen two or three others since I got mine in 2006.

Rod
 

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Discussion Starter #5
HI, thanks for the welcome and the in depth response.

Before this problem arose I only had front lights working, as you suggested, I ran an earth from the rear light to a frame earth which then brought in the horn, rear light and brake light, I thought I was done, but that's when I noticed the current problem I have.

I have fitted a 679 lamp on a polished ally casting and you guessed it, a 88SA rotary lighting switch which is correct for the year.

The rear light is connected correctly, rear light on and brighter brake light on when the rear brake is applied.

Regards.

Pete
 

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If it is home market TR6 and not the export TR6R feel free to post some pics. I think I've only seen two or three others since I got mine in 2006.

Rod
Hi Rod

I'll get some pics up when I have sorted the electrics out and have all the panels back on.

Regards.

Pete
 

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Hi Pilonpete electrical problems can be so frustrating I know I've been there so many times.what Stuart says about dedicated Earth wires is probably the best bit of advice you will ever get regarding wiring .I've taken it to the extreme on my T140 I have 3 Earth wires connected to battery going to 3 points on bike everything has dedicated Earth going to 1 of these points and the 3 points are connected to each other with wires between each point.all ends connected to bike with brass rings.good luck tracing your fault and pay heed to Stuart he knows his stuff.
 

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Discussion Starter #8
Hi Pilonpete electrical problems can be so frustrating I know I've been there so many times.what Stuart says about dedicated Earth wires is probably the best bit of advice you will ever get regarding wiring .I've taken it to the extreme on my T140 I have 3 Earth wires connected to battery going to 3 points on bike everything has dedicated Earth going to 1 of these points and the 3 points are connected to each other with wires between each point.all ends connected to bike with brass rings.good luck tracing your fault and pay heed to Stuart he knows his stuff.
Hi Jonnner, I have run separate earths for the rev counter/speedo lights and now for the rear light, I think I'll take your advice and go further as you have to make sure there are solid earths everywhere, such a nightmare, thanks Pete
 

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Hi Pete,

ran an earth from the rear light to a frame earth
It might be only the way you've written it, but you know the frame isn't "earth"? It's the network of Red wires that should form the primary return path to battery +ve. I appreciate you might be connecting two or more Red wires on a bolt attached to the frame but that doesn't/shouldn't make the frame "earth".

ran an earth from the rear light to a frame earth which then brought in the horn,
Unless the horn's connected non-standard, that suggests an unsolved 'earth' problem somewhere.

As standard, the horn's electrically-isolated, because the Brown/Blue wire from battery -ve means the horn's 'live' all the time; the other horn terminal's connected to the handlebar button by the Brown/Black wire; it's the button not depressed that isolates the horn.

The problem with this arrangement has always been the (n) Lucas 'magic earth' between button and battery +ve. We know that, as standard, the next part of the return path is through the horn button/dipswitch body and its screw attachment to the handlebars. From the handlebars ... especially if they mounted in eyebolts and Metalastik bushes, your guess is as good as mine; however, it shouldn't need an 'earth' wire from the rear lamp to get the standard horn working ...

Ime, avoid all this ridiculous convoluted guesswork with a fifth, Red, wire alongside the standard four between the horn button/dipswitch and the main loom. However, the fiddly bit is locating where pressing the standard button contacts the switch body and soldering the end of the Red wire there but so it can't contact the dipswitch parts ... If you aren't confident, simply attach a (Red?) wire between a handlebar securing bolt and existing Red wires the main loom.

88SA rotary lighting switch
On the back of the ignition switch, Lighting switch Brown/White wire connected to the input Brown/White or the output White wires?

Have you double-checked the connections to the Lighting switch terminals?

rear light is connected correctly, rear light on and brighter brake light on when the rear brake is applied.
(y)

you have to make sure there are solid earths everywhere, such a nightmare,
Nope, this stuff is really, really basic and simple, just only ever needs a logical approach:-

. Triumph and its component suppliers like Lucas were geared only to getting a new bike through its warranty period with the least reduction in profit; that warranty period was a few months, the bikes then lasting a few more years without major problems that pissed-off new bike buyers was only a nice-to-have.

. Otoh, we expect any 'consumer durable', including these old heaps, to be much more 'durable' than their first owners over half-a-century ago? Absent Triumph or a dealer to apply modern quality-control standards, we have to do it. :)

. Risking stating the electrically-obvious, except for between the alternator and rectifier (or reg./rec.), every single circuit starts and ends at the battery - starts at battery -ve, ends at battery +ve (strange as that might seem).

. Up to '79, basically every single circuit on any of these old heaps had a non-Red wire from battery -ve to the component, be it ignition coil, bulb or horn.

. However, what these old heaps didn't always have was a Red wire from every ignition coil, bulb or horn to battery +ve.

. So, when an electrical component doesn't 'work', first you check if the component itself 'works' and, if it does, then you check its circuit from battery -ve to battery +ve.

. Part of that second check is looking for the Red wire to battery +ve:-

.. Reality says a points plate probably doesn't need a Red wire attached directly, but logic says the number of bare-metal, corrodable connections between the points plate and the Red wire completing the ignition circuit should be the absolute minimum - i.e. the Red wire attached to another engine component is better than the Red wire attached to a cycle part.

.. Otoh, any bulb absolutely does need a Red wire attached directly.

.. So applying similar logical steps to the horn circuit first highlights the absence of any logical, sensible electrical return path from handlebar button to battery +ve and then should've raised the question how a wire between rear lamp and battery can logically and sensibly make the horn (closer to the front of the bike as standard) work? ;)

Hth.

Regards,
 

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Discussion Starter #10
Hi Pete,


It might be only the way you've written it, but you know the frame isn't "earth"? It's the network of Red wires that should form the primary return path to battery +ve. I appreciate you might be connecting two or more Red wires on a bolt attached to the frame but that doesn't/shouldn't make the frame "earth".


Unless the horn's connected non-standard, that suggests an unsolved 'earth' problem somewhere.

As standard, the horn's electrically-isolated, because the Brown/Blue wire from battery -ve means the horn's 'live' all the time; the other horn terminal's connected to the handlebar button by the Brown/Black wire; it's the button not depressed that isolates the horn.

The problem with this arrangement has always been the (n) Lucas 'magic earth' between button and battery +ve. We know that, as standard, the next part of the return path is through the horn button/dipswitch body and its screw attachment to the handlebars. From the handlebars ... especially if they mounted in eyebolts and Metalastik bushes, your guess is as good as mine; however, it shouldn't need an 'earth' wire from the rear lamp to get the standard horn working ...

Ime, avoid all this ridiculous convoluted guesswork with a fifth, Red, wire alongside the standard four between the horn button/dipswitch and the main loom. However, the fiddly bit is locating where pressing the standard button contacts the switch body and soldering the end of the Red wire there but so it can't contact the dipswitch parts ... If you aren't confident, simply attach a (Red?) wire between a handlebar securing bolt and existing Red wires the main loom.


On the back of the ignition switch, Lighting switch Brown/White wire connected to the input Brown/White or the output White wires?

Have you double-checked the connections to the Lighting switch terminals?


(y)


Nope, this stuff is really, really basic and simple, just only ever needs a logical approach:-

. Triumph and its component suppliers like Lucas were geared only to getting a new bike through its warranty period with the least reduction in profit; that warranty period was a few months, the bikes then lasting a few more years without major problems that pissed-off new bike buyers was only a nice-to-have.

. Otoh, we expect any 'consumer durable', including these old heaps, to be much more 'durable' than their first owners over half-a-century ago? Absent Triumph or a dealer to apply modern quality-control standards, we have to do it. :)

. Risking stating the electrically-obvious, except for between the alternator and rectifier (or reg./rec.), every single circuit starts and ends at the battery - starts at battery -ve, ends at battery +ve (strange as that might seem).

. Up to '79, basically every single circuit on any of these old heaps had a non-Red wire from battery -ve to the component, be it ignition coil, bulb or horn.

. However, what these old heaps didn't always have was a Red wire from every ignition coil, bulb or horn to battery +ve.

. So, when an electrical component doesn't 'work', first you check if the component itself 'works' and, if it does, then you check its circuit from battery -ve to battery +ve.

. Part of that second check is looking for the Red wire to battery +ve:-

.. Reality says a points plate probably doesn't need a Red wire attached directly, but logic says the number of bare-metal, corrodable connections between the points plate and the Red wire completing the ignition circuit should be the absolute minimum - i.e. the Red wire attached to another engine component is better than the Red wire attached to a cycle part.

.. Otoh, any bulb absolutely does need a Red wire attached directly.

.. So applying similar logical steps to the horn circuit first highlights the absence of any logical, sensible electrical return path from handlebar button to battery +ve and then should've raised the question how a wire between rear lamp and battery can logically and sensibly make the horn (closer to the front of the bike as standard) work? ;)

Hth.

Regards,
 

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Discussion Starter #11
Hi Guys,

I have just found the problem, feel a bit stupid now, whilst checking through the wiring, and running independent earths, I noticed that where the 2 wires coming from the stop lamp switch meet the 2 from the loom I had connected them with a double connector, just split them out and all's well.

Many thanks for your help and suggestions, really much appreciated.

Stay safe.

Regards..

Pete
 

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I have just found the problem, feel a bit stupid now
Ha, don’t worry about that. Whilst mulling over Stuart’s guidance on re-wiring my bike I couldn’t get my head around the use of 2, 3 and 4 way sleeve connectors for the red return circuit. Only when I realised that inside the sleeve it’s just one connection did it make sense.
 

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Hi Guys, I am coming to the end of a total rebuild of a 1966 TR6 and have encountered an electrical fault that has baffled me for the past 2 weeks.
When I turn the ignition switch on, lighting switch is off, the rear light comes on together with the speedo and rev counter lights.
I have gone over the wiring diagram so many times but cannot find the problem.

Your thoughts and suggestions would be much appreciated, cheers.

Pilonpete
Disconnect brake light switches
 
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