Help! Wiring harness problems - '60 A10

[bsaketcase650]

This is driving me bonkers! I have made a wiring harness and have fitted it exactly as per the BSA service sheets (sheet 808A). The only deviation from original is a ground cable from the tail light unit and an in-line fuse between battery and earth.
The issue that I have is as follows. Everything appears to be working as it should except for the rear brake light switch. When I depress the brake pedal the tail light illuminates, but so does the pilot light and speedo light!
What have I done wrong??
Anyone out there who is handy with the 'sparks' please advise before what little hair I have left gets pulled out!

Regards

Simon

[fido]

If you take the lens off the rear light you should be able to see which filament is coming on. Try first with the lights to see which is the tail light filament then turn the lights off and press the brake pedal. If both filaments light up you need to check your tail lamp ground wire as it may not be making a good contact.

[a101960]

I agree with Fido your problem is a bad earth path.

[bsaketcase650]

Thanks for the speedy replies. I have checked the ground wire running from the tail light unit through to the earthing point on the frame. It seems fine. I have checked the stop/tail light bulb and both filaments illuminate on both the brake pedal and from the light switch.
On looking at the wiring diagram it seems that lighting circuit becomes live as soon as the brake pedal switch in activated. How does the current differentiate between which filament to illuminate and how is it , in a system working correctly, does the tail light/pilot light circuit isolate itself from the brake light? I thought the wiring circuit looked very simple but clearly I'm dong something wrong. Doh!

Simon

[bsa-bill]

If you look at the wireing diagram you will see the brake light circuit comes from the Ampmeter via the brake switch to the rearlamp brake filament, the rearlight filament comes via the light switch, the feed to the light switch comes from the opposite side of the ampmeter ( the side that is fed from the regulator )
If you had the brake light wire and the wire to the light switch from the SAME side of the ampmeter then you would get the symptoms you described.
something to chaeck anyway
Also check you have wired the light switch correctly.

I am notorious at reading emails wrongly so forgive me if I have this all wrong but your last comment might suggest that there is only one wire to the rear light, there are two plus of course your extra earth making three in total.

Running an extra earth from the rear light is a very good idea, also run one from your headlight otherwise the electicity has to fight its way through the grease in your head bearings.

All the best -- Bill

[bsaketcase650]

Cheers for the advice Bill.
I do in fact have three wires to the tail light unit, the feed from brake light switch, feed from the light switch and ground wire running from one of the fixing studs of the light unit to the frame earth point.
This has me baffled. As an experiment I found the old and rusted tail light and having fitted a new bulb I powered it direct from the battery and only one of the filaments illuminated. I'm beginning to wonder if the 'new' tail light unit is the source of the problem.

Simon

[bsa-bill]

Ah sorry for the misunderstanding Simon. Possible that it is the light unit but have you tried the new bulb in it

All the best - Bill

[fido]

It's easy enough to check the new lamp if you connect battery wires direct to it like you did for the old one 

[BSA_54A10]

As fido said, verify the new lamp with a battery so that you will at least know  weather the problem is in your wiring or in the new tail lamp.

I would tend to suspect the latter.
Lucas no longer make tail lamps for industry where they would have been subject to both their own quality control and that of the bike factory.
Just about all electrics are now made by after market suppliers and as Pommie bike riders are with out a doubt the cheapest , tightest walleted bunch of consumers nearly all after market parts made for shops are the cheapest lousiest piece of crap that they can possibly make because that is all we are willing to pay for.

Every repo tail lamp I have bought over the years has needed substantial rectification before it was suitable for use.
If you push out the terminals and look at the back there is a good chance that the wires have a substantial bare section . Add to that the fact that the insulation board is about 1/2 the thickness of the original Lucas part then you have a short circuit in the making.
It is now S O P  for me to remove the wires from an old lamp holder and the new one and substitute the new insulator with the old one. Even the Japaneese lamp holders from my L300 are better quality that the junk that the bike shops foister on us now days.

OTOH the "bulbs that last forever" replacement units are excellent quality and well worth the money although their Lucas replacements have twice gone out of production because Pommie bike owners will not pay a fair price for a perfect product that will literally last forever.

(wipes foam away from mouth gets down of soap box and waits for tyrade of flame emails ) 

[bsa-bill]

BSA_54A10 could you please prefix your Pommie remarks with the word "some" I would then tend to agree with you that some Pommie bike riders are tight, I do object to being lumped in with them though ( I have receipts that I have never dared add up that would testify that I get the best product I can ).
This is a nice gentle, informative and helpfull forum and I for one would like it to stay that way and NOT get into the bitter tit for tat posts that spoil many other lists.
Suggest you put your soap box on the Barbie and consider this not so much a flame more a warm reply 

All the best - Bill

[bsaketcase650]

Problem solved! I thought the solution would be something simple or stupid! It turned out to be both. On removing the tail light I realized that the cables from the light had been linked to the harness by a double snap connector instead of two separate connectors! Result power passing through both sides of the light circuit.  Feel like a right div!! Everything working perfectly now.
Many thanks for all your contributions.

Simon

[RichardL]

Simon,

I think your problem might be that the double connector you are using could be of the connected type rather than the separated type. OOPS! You already know that. Ah, the satisfaction I would have had if only I could I have guessed it aforehand. No need for embarrassment. It's good troubleshooting. Speaking for myself, I've done much dumber, and I would risk saying that the rest of our little group would say the same.

Richard L.

[NickSR]

Hi Simon

Great news you have got things sort, it was good to see the replys of advice that you recived.

Regards
Nick

[BSA_54A10]

Good to see that you have it sorted

Lucky it isn't an alternator model.
Want to guess how many faulty alternators ended up being a replacement 4 way bullet instead of a 4 gang bullet.
To overcome these little problems I now use ganged spade connectors.
The gang boxes usually come from dumped cars with new uninsulated terminals installed.
It is worth the effort to do.
If you ferret around enough you should be able to find "T & U " shaped gang blocks.
I use the T on the battery then paint the terminal with "liquid electrical tape" ( no more corroded battery terminals ) and the U on the tail lamp in both cases the terminal that goes across ( top of the T and bottom of the U ) for the earth so there is no chance of mixing up the connections. I use a U inside the headlamp as well High on one upright, low onthe other and extra earth on the bottom.
On the WD M20 it has made a massive difference as the headlamp now gets 6 V ( from battery ) or 7 V when the generator is running. Prior to the rewire there was 4V at the headlamp ( nicknamed  candle ).

Battery  With  Plug


Three way on tail lamp

[olev]

Bit off topic??
A trick I was taught long ago. When rewiring a bike, wire your high/low beam elements through a  change over relay. The relay is fast to act and will always be either in high beam or low beam. Its less exciting as you won't be left in the dark if you have a dicky switch.
cheers