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#493557 - 06/10/13 1:52 am 1978 t140e wiring harness.  
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Magnolia, TX
Installing a new wiring harness on my bike and have a couple of questions.
In the wiring bundle coming from the right hand kill switch cluster there is a white wire with a red stripe that I can't find on the wiring diagram. Does it connect to anything?
On the harness side for that switch there are three white wires. I know one goes to the white for the kill switch and one goes to the white for the front brake switch. What does the third one go to?
On the head light lead there is a blue/yellow wire, a double green/brown and a white/brown. What numbers on the switch poles do they go to?


1978 Bonneville T140E
1974 Trident
1970 BSA Thunderbolt
1971 Norton Commando
1972 Norton Commando
2-1974 Norton Commandos
2004 XL 1200R Sportster

Everything will be alright in the end. If its not alright, its not the end.
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#493568 - 06/10/13 9:03 am Re: 1978 t140e wiring harness. [Re: htown]  
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Originally Posted By htown
In the wiring bundle coming from the right hand kill switch cluster there is a white wire with a red stripe that I can't find on the wiring diagram. Does it connect to anything?


No, not on a T140, as it's an electric starter wire. The wire will be live/hot when the particular switch cluster button is pressed, so tape it up.

Originally Posted By htown
On the harness side for that switch there are three white wires. I know one goes to the white for the kill switch and one goes to the white for the front brake switch. What does the third one go to?

On the head light lead there is a blue/yellow wire, a double green/brown and a white/brown. What numbers on the switch poles do they go to?


There are a number of options for the following connections due to the different switch types used by Triumph, however, if the switch is 35701(A) then I would suggest the following:

For lights operated independently, not controlled by the ignition switch (direct from the battery). For this arrangement, the brown/white [NW] and brown/blue [NU] wires must be connected to the "common" terminal on the ignition switch as shown in the factory manual wiring diagram H22 (pdf p.191).

http://www.classicbike.biz/Triumph/Repair/1970s/73-78-Triumph-Bonneville-Tiger-Workshop-Manual.pdf

For Edit: 35701A 35710A switch

Brown/green (not green/brown) = 4
Brown/white (not white/brown) = 1 or 7
Blue/yellow = 8
White = Disconnected


If you want the lighting function to be controlled by the ignition switch (lights on only when ignition is on).

Brown/green = 4
Brown/white = Disconnected.
Blue/yellow = 8
White = 1 or 7

#493647 - 06/10/13 9:45 pm Re: 1978 t140e wiring harness. [Re: htown]  
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Thanks for the info LAB.


1978 Bonneville T140E
1974 Trident
1970 BSA Thunderbolt
1971 Norton Commando
1972 Norton Commando
2-1974 Norton Commandos
2004 XL 1200R Sportster

Everything will be alright in the end. If its not alright, its not the end.
#493736 - 06/11/13 6:34 pm Re: 1978 t140e wiring harness. [Re: L.A.B.]  
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Hi guys,

I'm puzzled ... confused

Originally Posted By: L.A.B.

That page shows a 34419 switch, as catalogued '73-'78? Switch 35710(A) was used 'til the end of the '70 season?

Also, I thought the T140E was '79-on, with the '78 T140 model being a 'V' ... although I appreciate an early '79-season bike actually constructed in the later months of 1978 could also have been registered in 1978 ... but I thought 'E's had completely different lighting switches - pilot and tail lamps switched by the between-the-clocks key switch and black handlebar switch clusters with the headlamp on/off switch in the right cluster?

Regards,

#493742 - 06/11/13 7:13 pm Re: 1978 t140e wiring harness. [Re: htown]  
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Magnolia, TX
1978 model year bikes made after Jan 1,78 are a bit a mash up of parts. They have the EPA mandated parallel port head and Mark II carbs, but the rest of the bike is basic 1978 spec including points, the earlier switch gear with ignition switch on the headlight mount and headlight switch on the bucket. They also have Smith's clocks. With the start of the 79 model year bikes in Sept 78 the switch was made to the Rita ignition, a different alternator and the newer switch gear and Veglia clocks.
It makes ordering parts pretty tricky. I was able to find an original late 78 parts supplement book which help me sort things out. What is interesting in that book is that it calls for the 31788 switch and specifies a set of wiring leads and diode part number 60-7079 to wire it for headlights on with the ignition switch. Probably a work around at the time.
I'm really not sure what switch is on my bike right now, it looks like a repop and doesn't have a part number on it. I think though with LAB's guide I can wire it for lights on with ignition.

Last edited by htown; 06/11/13 7:24 pm.

1978 Bonneville T140E
1974 Trident
1970 BSA Thunderbolt
1971 Norton Commando
1972 Norton Commando
2-1974 Norton Commandos
2004 XL 1200R Sportster

Everything will be alright in the end. If its not alright, its not the end.
#493748 - 06/11/13 7:29 pm Re: 1978 t140e wiring harness. [Re: Stuart]  
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Originally Posted By Stuart
I'm puzzled ... confused

Originally Posted By L.A.B.

That page shows a 34419 switch, as catalogued '73-'78?


Yes.

Originally Posted By Stuart
Switch 35710(A) was used 'til the end of the '70 season?


My typo, should have been 35710A.

Curiously, they are also found on late V models, and maybe also '78 E models (see below).


Originally Posted By Stuart
Also, I thought the T140E was '79-on, with the '78 T140 model being a 'V' ... although I appreciate an early '79-season bike actually constructed in the later months of 1978 could also have been registered in 1978 ... but I thought 'E's had completely different lighting switches - pilot and tail lamps switched by the between-the-clocks key switch and black handlebar switch clusters with the headlamp on/off switch in the right cluster?


T140"E" model production actually commenced during mid-'78 season (around Dec.'77/Jan. '78) these E's have an "X" (1978) season code stamp, so there are "1978 season" T140E models.

With the exception of the parallel inlet port cylinder head, AMAL MkII carbs, and breather arrangement, etc. the specification of the "78" E was basically the same as the '78 spec. T140V (that Meriden also continued to produce until the end of the '78 season). These '78 E models normally had points ignition and a positive earth electrical system, same as the '78 V model.

http://www.britbike.com/ubb/noncgi/ultimatebb.php?/ubb/get_topic/f/13/t/004984/p/1.html#000005


#493766 - 06/11/13 10:23 pm Re: 1978 t140e wiring harness. [Re: htown]  
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The switch to the parallel port head and Mark II carbs, t140e, was mandated by the US EPA emission standards which took effect for all motorcycles on 1/1/78. Any bikes sold in the US after that date had to be certified as passing the emission test. The rest of the bike was basically the
same.
LAB, are you saying that the did not switch the entire production to the E model but continued to build the V model for sale in other markets than US?


1978 Bonneville T140E
1974 Trident
1970 BSA Thunderbolt
1971 Norton Commando
1972 Norton Commando
2-1974 Norton Commandos
2004 XL 1200R Sportster

Everything will be alright in the end. If its not alright, its not the end.
#493849 - 06/12/13 5:21 pm Re: 1978 t140e wiring harness. [Re: htown]  
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Hi,

Firstly, thanks for the run-down on the '78 T140E - another day when I learnt something new. grin

Originally Posted By: htown
I was able to find an original late 78 parts supplement book
What is interesting in that book is that it calls for the 31788 switch
I'm really not sure what switch is on my bike right now, it looks like a repop and doesn't have a part number on it.

The Lucas switches have a black plastic casing on the part inside the headlamp shell, on which the eight individual terminal numbers and the five-figure number are moulded very small; frown you might want to examine that casing under a bright light, either on or off the bike, and possibly with a magnifying glass ... wink

Afaict, 31788 and 35710 are interchangeable but 35710 is listed more widely - across the range from '68 to '70 and continuing on the T100 'til '74 while 31788 seems to have been listed previously only on the '70 T150.

Originally Posted By: htown
I think though with LAB's guide I can wire it for lights on with ignition.

With both '69 (using 35710) and '70 (using 31788) Triumphs, you'll pardon a little scepticism ...

If your bike's switch is a "repop", there isn't any guarantee its internal contacts are configured the same as a 35710/31788. To my certain knowledge, BSA, NVT and the Co-op (so including most incarnations of Triumph wink ) used at least four different versions of that toggle switch just from '68 onwards, all are 57SA but all have different 5-figure numbers and cover three different non-interchangeable configurations. On top of that, versions of the 57SA toggle switch (but with other 5-figure numbers) were used widely certainly on 1960's and 1970's British cars, 4WD, vans and trucks (e.g. iirc 31788 is actually listed by Lucas for switching fuel tanks on certain models of Land Rover! grin ).

Originally Posted By: L.A.B.
For lights operated independently, not controlled by the ignition switch (direct from the battery).

Brown/green (not green/brown) = 4
Brown/white (not white/brown) = 1 or 7
Blue/yellow = 8
White = Disconnected

If you want the lighting function to be controlled by the ignition switch (lights on only when ignition is on).

Brown/green = 4
Brown/white = Disconnected.
Blue/yellow = 8
White = 1 or 7

Les might have good reasons for this advice but he hasn't explained them; they aren't the connections Triumph (or BSA) used.

Imho, first you need to establish whether your bike's toggle switch has the same connections (internal and external) as 35710/31788. If you would like to see a diagrammatic representation, '63-'70 650 workshop manual (pages H30/H31) or '63-'74 350 & 500 workshop manual (pages HH8/HH9/HH10).

If it does, ime input (Brown/White or White) was never connected to terminal 1; 35710/31788 have internal connections between 1, 3, 5 and 7; when off or 'pilot on', 5 is connected to 6; so, if you connect the input to terminal 1, terminal 6 will be live when the switch is supposed to be 'off' and terminal 7 will be live whatever position the switch is in. confused

The significance of 7 is that's supposed to be the terminal you attach Brown/Green to. The significance of 6 is that was the terminal the pilot lamp was supplied from. The significance of that is 35710 and 31788 can switch the pilot lamp off when the headlamp (terminal 8) is on and vice versa; you don't have to use this feature on your bike but it's there if you want it.

Amalgamating what your bike has with what Triumph did when 35710/31788 were used previously:-

Blue/Yellow (to handlebar dipswitch) = 8
Brown/Green (to tail lamp, instrument lamps and - unless changed by you - pilot lamp) = 7
Input = 4

As Les advised:-

. "For lights ... not controlled by the ignition switch", 'Input' should be Brown/White;

. "If you want the lighting function to be controlled by the ignition switch", 'Input' should be White.

Originally Posted By: L.A.B.

At the risk of labouring the point, the 57SA toggle switch shown in this diagram is 34419; it allows for two inputs, Brown/White to 3 and White to 7; 35710/31788 do not allow for two inputs.

Originally Posted By: htown
LAB, are you saying that the did not switch the entire production to the E model but continued to build the V model for sale in other markets than US?

Seems sensible. Triumph couldn't control parts quantities when they were producing tens of thousands of bikes every year - look at how many bikes built either early or late in a year have parts from the previous or next year's models. The chances of that improving when they were producing just a fraction of those numbers with a fraction of the old workforce seems remote. So it made sense to carry on producing 'V's for the markets that'd take 'em, 'til nearly(?) all the 'V' parts were used up?

Hth.

Regards,

#493855 - 06/12/13 5:59 pm Re: 1978 t140e wiring harness. [Re: htown]  
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Originally Posted By: htown
LAB, are you saying that the did not switch the entire production to the E model but continued to build the V model for sale in other markets than US?


Yes.

#493865 - 06/12/13 7:12 pm Re: 1978 t140e wiring harness. [Re: Stuart]  
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Originally Posted By: Stuart
The Lucas switches have a black plastic casing on the part inside the headlamp shell, on which the eight individual terminal numbers and the five-figure number are moulded very small;


The switch number (and WW/YY date) is often stamped on the metal part of the switch.





Originally Posted By: Stuart
Les might have good reasons for this advice but he hasn't explained them;


I didn't see a reason for any further explanation, either it is a 35710, in which case it should work when connected as I suggested, or, it won't.


Originally Posted By: Stuart
they aren't the connections Triumph (or BSA) used.


That's because the 35710A switch doesn't have the same tab connectors as shown on either T140 wiring diagram. The 35710A switch has no tabs at 2,3 and 5,

Here's JBMorris' "Early '78 season" T140V switch, apparently the same type switch as my own "Late '78 season" T140V (note the Brown/White connected to T1).

Originally Posted By: JBMorris
This shot shows the back of the headlamp switch:



Originally Posted By: JBMorris
The headlight switch is 35710A 35 77





Originally Posted By: Stuart
If it does, ime input (Brown/White or White) was never connected to terminal 1;


Well you can't connect brown/white to terminal "3" of the 35710 switch because it doesn't have a terminal "3" (see JBMorris photo)".



Originally Posted By: Stuart
35710/31788 have internal connections between 1, 3, 5 and 7; when off or 'pilot on', 5 is connected to 6; so, if you connect the input to terminal 1, terminal 6 will be live when the switch is supposed to be 'off' and terminal 7 will be live whatever position the switch is in. confused


Correct. Only, nothing is normally connected to terminal 6 on a T140 (again see JBMorris photo) however it is wise to insulate the "6" spade as it can short to the headlamp reflector if not insulated, or at least bent out of harm's way.





Originally Posted By: Stuart
Originally Posted By: htown
LAB, are you saying that the did not switch the entire production to the E model but continued to build the V model for sale in other markets than US?

Seems sensible. Triumph couldn't control parts quantities when they were producing tens of thousands of bikes every year - look at how many bikes built either early or late in a year have parts from the previous or next year's models. The chances of that improving when they were producing just a fraction of those numbers with a fraction of the old workforce seems remote. So it made sense to carry on producing 'V's for the markets that'd take 'em, 'til nearly(?) all the 'V' parts were used up?


I don't think it was a case of using up "V" parts? If it was, then it took them over 6 months to do so.

As I see it, there would be no good reason to manufacture the interim (and probably more expensive) "E" model for other markets that were not subject to the '78 US EPA regulations.

Last edited by L.A.B.; 06/12/13 8:34 pm.
#493878 - 06/12/13 10:44 pm Re: 1978 t140e wiring harness. [Re: htown]  
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Thanks for the pictures. I have the 35710A type, though it is a repop and has no part number on it. It is missing the 2,3 and 5 tabs. I now have it wired like the picture except I'm using a switched power white lead on the 1 terminal. Good point on covering the 6 tab. It may be several months before I have a battery in the bike to check it out.


1978 Bonneville T140E
1974 Trident
1970 BSA Thunderbolt
1971 Norton Commando
1972 Norton Commando
2-1974 Norton Commandos
2004 XL 1200R Sportster

Everything will be alright in the end. If its not alright, its not the end.
#493879 - 06/12/13 11:16 pm Re: 1978 t140e wiring harness. [Re: L.A.B.]  
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Hi Les,

Originally Posted By: Stuart
Les might have good reasons for this advice but he hasn't explained them;

Originally Posted By: L.A.B.
I didn't see a reason for any further explanation, either it is a 35710, in which case it should work when connected as I suggested, or, it won't.

I certainly cannot get the two 35710's I have to work as you suggested; because 1, 3, 5 and 7 are connected together internally, when I attach a supply ('78 T140E Brown/White or White) to 1, other terminals are 'live' when they shouldn't be or 'not live' when they should be. frown

Otoh, if I make connections exactly as Triumph (and BSA) did when they used 35710 between '68 and '74, the switches work and, moreover, they works exactly as anyone familiar with the switch type would expect them to work. bigt 'Fraid I don't see the point of complicating something simple and working ...

Originally Posted By: Stuart
they aren't the connections Triumph (or BSA) used.

Originally Posted By: L.A.B.
That's because the 35710A switch doesn't have the same tab connectors as shown on either T140 wiring diagram. The 35710A switch has no tabs at 2,3 and 5

confused As I pointed out in my previous post, the switch "shown on either T140 wiring diagram" is a 34419; it does not matter that "the 35710A switch doesn't have the same tab connectors as [34419]" because you cannot substitute one for the other directly.

Originally Posted By: Stuart
input (Brown/White or White) was never connected to terminal 1;

Originally Posted By: L.A.B.
you can't connect brown/white to terminal "3" of the 35710 switch because it doesn't have a terminal "3"

confused Why would you want to connect Brown/White to terminal 3 of a 35710? You can connect Brown/White to terminal 3 of a 34419 because, when a 34419 is operated, internally the Brown/White connected to terminal 3 supplies the Brown/Green connected to terminal 4.

However, on a 34419, terminal/position 3 is not permanently connected internally to 1, 5 and 7, as it is on 35710/31788. That is why, on a 34419, you can connect another supply (White) to terminal 7 and have it supply terminal 8 only when the toggle is in the 'headlamp' position, but you cannot on a 35710/31788.

If you want to connect Brown/White to a 35710 switch, why would you not connect it to terminal 4, as Triumph and BSA did originally and it probably still is on 99.9999% of other 35710/31788 switches? confused Once again risking labouring a point, that's how my Triumphs with these switches have been for many years, without any problems.

Originally Posted By: L.A.B.
Here's JBMorris' "Early '78 season" T140V switch, apparently the same type switch as my own "Late '78 season" T140V

1. I missed this in the original thread, otherwise I would've questioned it there.

2. Afaik, you're competent with your bikes' electrics. If you choose to copy on your bike(s) a mod. that you've read about on the www, that's up to you.

3. However, I question the wisdom of advising that mod. unqualified when, in the first place, we don't know "htown's" electrical confidence and competence, and we won't know the electrical confidence and competence of others who might read it.

Nevertheless, two wiring methods are now published, the 'KISS' method and the 'complicated' method; the reader can choose for him/herself.

Hth.

Regards,

#493983 - 06/13/13 5:06 pm Re: 1978 t140e wiring harness. [Re: Stuart]  
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Originally Posted By: Stuart
I certainly cannot get the two 35710's I have to work as you suggested; because 1, 3, 5 and 7 are connected together internally, when I attach a supply ('78 T140E Brown/White or White) to 1, other terminals are 'live' when they shouldn't be or 'not live' when they should be. frown


Otoh, if I make connections exactly as Triumph (and BSA) did when they used 35710 between '68 and '74, the switches work and, moreover, they works exactly as anyone familiar with the switch type would expect them to work. bigt 'Fraid I don't see the point of complicating something simple and working ...


Obviously, you still don't get it, (or you haven't been following this closely enough) I don't know which?




Originally Posted By: Stuart
Originally Posted By: L.A.B.
That's because the 35710A switch doesn't have the same tab connectors as shown on either T140 wiring diagram. The 35710A switch has no tabs at 2,3 and 5

confused As I pointed out in my previous post, the switch "shown on either T140 wiring diagram" is a 34419;


Yes, I know, however, there's a good deal of evidence that strongly suggests the 34419 switch was not the switch usually fitted to the later "V" models, it was 35710A.



Originally Posted By: Stuart
input (Brown/White or White) was never connected to terminal 1;

Originally Posted By: L.A.B.
you can't connect brown/white to terminal "3" of the 35710 switch because it doesn't have a terminal "3"


Originally Posted By: Stuart
confused Why would you want to connect Brown/White to terminal 3 of a 35710? You can connect Brown/White to terminal 3 of a 34419 because, when a 34419 is operated, internally the Brown/White connected to terminal 3 supplies the Brown/Green connected to terminal 4.


You still appear to be missing the point, that the 34419 seems not to have been the switch commonly found fitted to the '78 models regardless of what the parts books say.

Originally Posted By: Stuart
However, on a 34419, terminal/position 3 is not permanently connected internally to 1, 5 and 7, as it is on 35710/31788. That is why, on a 34419, you can connect another supply (White) to terminal 7 and have it supply terminal 8 only when the toggle is in the 'headlamp' position, but you cannot on a 35710/31788.

If you want to connect Brown/White to a 35710 switch, why would you not connect it to terminal 4, as Triumph and BSA did originally and it probably still is on 99.9999% of other 35710/31788 switches? confused Once again risking labouring a point, that's how my Triumphs with these switches have been for many years, without any problems.


You are still missing the point.


Originally Posted By: Stuart
If you choose to copy on your bike(s) a mod. that you've read about on the www, that's up to you.


Nothing whatsoever to do with reading the www. If the 35710A was commonly fitted as it seems to be, then what I suggested to htown isn't a "mod."


Originally Posted By: htown
I have the 35710A type, though it is a repop and has no part number on it. It is missing the 2,3 and 5 tabs.


Now, what was it again you were saying about the KISS method, Stuart?






Last edited by L.A.B.; 06/13/13 6:01 pm.
#494036 - 06/14/13 2:16 am Re: 1978 t140e wiring harness. [Re: L.A.B.]  
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Hi Les,

Originally Posted By: L.A.B.
you still don't get it,

Originally Posted By: L.A.B.
You still appear to be missing the point,

Originally Posted By: L.A.B.
You are still missing the point.

Originally Posted By: L.A.B.
the switch usually fitted to the later "V" models, it was 35710A.

No, it is you that's missing the point:-

1. If you find a "the later "V" model" (or early "E" model) with a lighting toggle switch numbered 35710 (or 31788), that switch will be exactly the same as a switch numbered 35710 (or 31788) that Meriden or Small Heath fitted to a bike built in the '68, '69 and '70 seasons.

2. Ime, if two Lucas 57SA toggle switches have the same 5-figure number on the outside, their internal connections are the same. I suspect that's why Lucas used the system.

3. When Meriden and Small Heath fitted the lighting toggle switch numbered 35710 (or 31788) in the '68, '69 and '70 seasons:-

a. the supply from the ignition key switch was connected to terminal 4;

b. the Brown/Green cable/s was/were connected to terminal 7;

c. the headlamp dipswitch supply cable was connected to terminal 8.

4. The words used at 3. have been chosen very carefully:-

a. on the aforementioned "later "V" model (or early "E" model)", "the supply from the ignition key switch" can be either unswitched Brown/White or switched White, as you advised earlier in this thread;

bi. on the aforementioned "later "V" model (or early "E" model)", "the Brown/Green cable/s" can include the one to the pilot light, or not, as the individual bike owner decides;

ii. if the individual bike owner decides he (or she) would like his (or her) bike's switch to turn off the pilot light when the headlight is on and vice versa, he (or she) can connect a separate pilot light supply cable to terminal 6; if not, your advice to insulate switch terminal 6 might or might not be apposite;

c. on the aforementioned "later "V" model (or early "E" model)", "the headlamp dipswitch supply cable" can be Blue/Yellow, rather than the '68, '69 and '70 wiring diagrams' Blue.

Originally Posted By: Stuart
If you choose to copy on your bike(s) a mod. that you've read about on the www, that's up to you.

Originally Posted By: L.A.B.
Nothing whatsoever to do with reading the www. If the 35710A was commonly fitted as it seems to be, then what I suggested to htown isn't a "mod."

You're seriously suggesting that, just eight years after Meriden last used exactly the same switch number(s), no-one still working there (or at Lucas) in 1978 could remember them and, if necessary, look up in a '68, '69 or '70 wiring diagram how the switch was connected then?

Otoh, you discount the possibility that, at some time in the last 35 years after a given bike left Meriden, an individual owner or mechanic (not necessarily familiar with '68/'69/'70 bike details), presented with disconnected wiring and a switch that doesn't appear how it should be in the wiring diagram for the bike, didn't get out a meter, paper and writing implement and cobble up the connections you've found? Particularly if that time coincided with one when 34419 switches weren't available?

And, 35 years on, you manage to extrapolate that to a "that's how they came from Meriden" point? shocked

Note I'm not suggesting that I am right and you are wrong (unlike the way your later posts have come across, even taking account that written English doesn't convey tone very well). What I am suggesting is there is more than one possibility and that, if a given reader feels that s/he might need to call on the services of someone experienced in Britbike electrics, there is a way of connecting up the 35710/31788 switches that is likely to be more recognizable to said someone experienced in Britbike electrics.

Originally Posted By: L.A.B.
Originally Posted By: htown
I have the 35710A type, though it is a repop and has no part number on it. It is missing the 2,3 and 5 tabs.

Originally Posted By: Stuart
the KISS method

I believe I've written the above in terms no-one could misunderstand. If nothing else, you should be able to note that, until the above quote, "2,3 and 5 tabs" are not mentioned in this post.

I suspect you've done so already but, if not, you're quite capable of going to the on-line copies of '68/'69/'70 wiring diagrams and noting that, when the then-standard 35710 or 31788 switch is fitted, "2,3 and 5 tabs" are not used.

Hth.

Regards,

#494101 - 06/14/13 5:08 pm Re: 1978 t140e wiring harness. [Re: Stuart]  
Joined: Mar 2006
Posts: 3,469
L.A.B. Online content
BritBike Forum member
L.A.B.  Online Content
BritBike Forum member

Joined: Mar 2006
Posts: 3,469
Norfolk, UK
Originally Posted By: Stuart
1. If you find a "the later "V" model" (or early "E" model) with a lighting toggle switch numbered 35710 (or 31788), that switch will be exactly the same as a switch numbered 35710 (or 31788) that Meriden or Small Heath fitted to a bike built in the '68, '69 and '70 seasons.


Did I say otherwise? I didn't mention anything about the 31788.

Originally Posted By: Stuart
2. Ime, if two Lucas 57SA toggle switches have the same 5-figure number on the outside, their internal connections are the same. I suspect that's why Lucas used the system.


Yes, so?

Originally Posted By: Stuart
3. When Meriden and Small Heath fitted the lighting toggle switch numbered 35710 (or 31788) in the '68, '69 and '70 seasons:-

a. the supply from the ignition key switch was connected to terminal 4;

b. the Brown/Green cable/s was/were connected to terminal 7;

c. the headlamp dipswitch supply cable was connected to terminal 8.

4. The words used at 3. have been chosen very carefully:-


Yes, I wouldn't disagree.


Originally Posted By: Stuart
a. on the aforementioned "later "V" model (or early "E" model)", "the supply from the ignition key switch" can be either unswitched Brown/White or switched White, as you advised earlier in this thread;


Yes, however, both the "early" and "late" T140V wiring diagrams show the switch has two power feeds, early shows White(switched) to 7, and Brown/Blue (unswitched) to 4, late shows White(switched) - 7, but Brown/White (unswitched) - 3.



Originally Posted By: Stuart
bi. on the aforementioned "later "V" model (or early "E" model)", "the Brown/Green cable/s" can include the one to the pilot light, or not, as the individual bike owner decides;



The feed to the pilot light is built-in to the harness Brown/Green as standard, what you are suggesting is making a modification to the lighting system, as the standard lighting arrangement for British bikes from 1971 was for the pilot light to remain on when the headlamp was on.


Originally Posted By: Stuart
ii. if the individual bike owner decides he (or she) would like his (or her) bike's switch to turn off the pilot light when the headlight is on and vice versa, he (or she) can connect a separate pilot light supply cable to terminal 6; if not, your advice to insulate switch terminal 6 might or might not be apposite;


Unless the individual wishes to use a higher output pilot bulb then I see no particular reason to wire the pilot separately, but again, to do so, would be a (possibly unnecessary) modification.



Originally Posted By: Stuart
You're seriously suggesting that, just eight years after Meriden last used exactly the same switch number(s), no-one still working there (or at Lucas) in 1978 could remember them and, if necessary, look up in a '68, '69 or '70 wiring diagram how the switch was connected then?


No, I didn't suggest that at all, but what ocurred '68-'70 is basically irrelevant-as things had changed because there is no separate pilot feed wire as standard from terminal 6 on a T140V as there was for '68-'70 and the '68-'70 arrangement still leaves a "live" unused terminal of a 35710/31788 switch.

Originally Posted By: Stuart
Otoh, you discount the possibility that, at some time in the last 35 years after a given bike left Meriden, an individual owner or mechanic (not necessarily familiar with '68/'69/'70 bike details), presented with disconnected wiring and a switch that doesn't appear how it should be in the wiring diagram for the bike, didn't get out a meter, paper and writing implement and cobble up the connections you've found? Particularly if that time coincided with one when 34419 switches weren't available?


Whether the 35710 switch is connected the way you suggest, or the way I suggest makes not one jot of difference to the actual lighting switch function and there will still be "live" unused terminals either way.



Originally Posted By: Stuart
And, 35 years on, you manage to extrapolate that to a "that's how they came from Meriden" point? shocked


No, simply that it doesn't matter-as far as switch operation is concerned, unless there is an intention to modify the wiring to the pilot light.

Originally Posted By: Stuart
Note I'm not suggesting that I am right and you are wrong (unlike the way your later posts have come across, even taking account that written English doesn't convey tone very well).


That may be be true, as you often come across as overly pompous and condescending but I may be misreading your tone? I don't believe I said you were wrong, but that you weren't getting my point, somehow I doubt you will now.



Last edited by L.A.B.; 06/14/13 6:55 pm.

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