G3LS wiring

Information relating to the Matchless G3 or AJS Model 16 350cc Heavyweight
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chrisg1988
Posts: 5
Joined: Mon May 31, 2021 8:14 am
Location: Malta

G3LS wiring

Post by chrisg1988 »

Good morning,

I am trying to sort out the wiring on my 54 G3LS. Basically I installed a new battery as the other one was flat. It is my first time switching on any of the electrics so I didnt knoif something was wrong with it or not. All I know is that the harness was changed in the 08 but the bike was never on the road from then so i do not know if it had been tested.

Anyways, I tried switching on everything and the following happened when taking power only from the battery:

Sidelamps very dim
Headlight very dim but both normal and bright work
Horn works
Ammeter works
Tail light and brake light do not work.

I checked the bulb on the tail light and it is good, brake light issue was determined to be slack in the brake light switch so that is no issue(tail light still doesnt work) .

In the mean time I noticed that the battery wires were very warm. Checked continuity between tail and switch all ok. Checked current draw between brake and brakelight and its good but from battery to the switch when I put the switch on sidelight the amperage will not show on the multimeter(must be a very heavy drain).

I opened the switch and noticed the wiring wasnt according to the manual(mainly ammeter wires was connected to no5 instead of 3 and sidelamps/speedo where on 3 instead of 5.). I turned them around and tried them. Sidelamps are a bit brighter, horn ok, headlight not working and tail not working. Wires still very warm. Ammeter still full deflection.

Any ideas? Could it be an earth problem?

Thanks

Christian
Groily
Member
Posts: 2151
Joined: Thu Jul 04, 2002 1:00 am
Location: NORMANDIE FRANCE

Re: G3LS wiring

Post by Groily »

There is certainly a serious fault somewhere! But it could take a bit of detective work to find it . . .

A typical dynamo system, on a bike with a magneto, looks like this:
Dynamo wiring diagram (typical).jpg
On an 'unknown' machine allegedly rewired 13 years ago but never used it seems, things definitely need checking properly.

The areas to look at first are the 'always live' wires that go battery to ammeter, ammeter to the switch position 3, and ammeter to regulator 'A'. If they are good, no shorts to earth from any of them, nothing squashed under the tank, hanging loose in the headlight, etc, then it's a good first step. They are most probably absolutely fine, or you'd have a permanent discharge as soon as the battery was connected up, and the ammeter reading negative all the time.

Then check that the live feeds for brakelight and horn are OK too, no shorts, and that there's no unwanted connection between the tail light and brakelight wires, or from either of them to earth due to something squashed under the rear mudguard (not uncommon!) or a mix up at the tail light unit (also not uncommon).
A good plan would be to disconnect terminal 5 at the switch to see if the speedo and tail don't come on (good, they shouldn't) but also to see if the other problems disappear.
Given that your problems start to occur with the light switch in the sidelight position, and then also in the headlight position too, I have a strong suspicion about this area. Especially as it's where the harness was wrongly connected.

Check - as you are - that the correct terminals take power to the dipswitch and front sidelight too. That's 'Power in' at Terminal 3, and then out through terminals 2 and 4 respectively. Also check that there isn't a short on the headlamp connector on the back of the bulb holder or a short off the sidelight holder. Check no wires are trapped and/or chafed under the tank, round the steering head, in the headlamp shell, etc.

If you follow things through methodically, doing one thing at a time, you'll almost certainly find the problem. But the very next thing I would do is fit a FUSE, on the live side of the battery, to include the take off for the brakelight (and horn if that's directly wired from the battery).
Hot Wires = High Risk, and even just one fuse may save a major meltdown. Were there a fuse in the loom, it would probably be blowing every time you turn anything on??

Good luck!
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chrisg1988
Posts: 5
Joined: Mon May 31, 2021 8:14 am
Location: Malta

Re: G3LS wiring

Post by chrisg1988 »

Hello Groily,

Thanks for the very comprehensive troubleshooting. That should keep me busy during the weekend, hopefully I'll find what's causing it. I agree on the fuse, I will be fitting that as soon as I resolve the issue as I already had an experience with the Lucas white smoke on my Triumph Herald once and it wasn't pleasant. As for the fuse, what Amperage should it be ideally?

Thanks and good weekend,

Christian
Groily
Member
Posts: 2151
Joined: Thu Jul 04, 2002 1:00 am
Location: NORMANDIE FRANCE

Re: G3LS wiring

Post by Groily »

For a fuse, I'd use a 15 or 20 amp one at 6v. A short will blow it, but turning everything on and tooting the horn won't! Lot of threads on this on the forum if you want to trawl through.
chrisg1988
Posts: 5
Joined: Mon May 31, 2021 8:14 am
Location: Malta

Re: G3LS wiring

Post by chrisg1988 »

Hello,

Found the main culprit, chafed tail light wire trapped under the voltage regulator bracket. Headlight sorted aswell, dip wire attached to the wrong terminal. It is working fine now both on battery and on dynamo, Ill just need to add a fuse. Hopefully Ill find one with a small cut out switch so so can use it as a quick disconnect for the battery when im not using it

Thanks for your help

Christian
Groily
Member
Posts: 2151
Joined: Thu Jul 04, 2002 1:00 am
Location: NORMANDIE FRANCE

Re: G3LS wiring

Post by Groily »

That's good news - Good luck!
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