AJS Model 14 Electrics.

Information relating to the Matchless G2 or AJS Model 14 250cc Lightweight
JohnR
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AJS Model 14 Electrics.

Post by JohnR »

I placed the question below on the general forum yesterday then realized that this is the more appropriate place for it.
Can any of you electrical gurus help me please. I have a recently purchased 1962 AJS model 14 CSR with Alternator and Coil Electrics. My battery is not new but seems ok but sometimes when I leave the bike and return the next day the battery is totally flat. There was no discharge showing on the ammeter and no switches including ignition left on. Where should I start to look for what appears to be a short,discharge or power drain.
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john
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AJS Model 14 Electrics.

Post by john »

Put a multi-meter on current setting in line with battery (series) with every thing turned off. The current drain should be very near zero; if it is then the battery will need replacing. If not then there is a drain or a wiring fault but we will cross bridge latter if we need too.

John T
lawrence
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AJS Model 14 Electrics.

Post by lawrence »

If you don't have a multi meter (very useful though, if not essential, and nowadays very cheap) just disconnect the battery overnight. If next day when you reconnect it the battery is dead, the battery is your problem. If when you connect it everything works then you have a fault in your electrical system.

My bet would be on a short somewhere. This is when your multi meter comes in handy, tracing said short.
JohnR
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AJS Model 14 Electrics.

Post by JohnR »

Hi John T.
Thanks for your comments and advice. I have got a friend to put a meter on the wiring as suggested and with all switches off a significant current is flowing. We then took the DC (brown connection) off the rectifier and repeated the test. There was no current flowing. Does this suggest that the rectifier is at fault.
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john
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AJS Model 14 Electrics.

Post by john »

Unfortunately I have not got the right wiring diagram to hand (I am looking 1962 heavy weight single diagram) but with the ignition switch off there should be no connection from the battery to the rectifier.

So I think the first place to look, armed with the correct wiring diagram, would be the ignition switch and wiring.

John T
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Biscuit
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AJS Model 14 Electrics.

Post by Biscuit »

John. can you offer an explanation of your statement that with everything off and no current drain, the battery needs replacing?



Don Madden
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AJS Model 14 Electrics.

Post by Don Madden »

I believe the battery is always connected to the rectifier. A short to earth is possible but in my experience, it is often a damaged rectifier.

Connecting a battery with reversed polarity for even a short time will cause melt-down of the diodes in the rectifier & can melt the insulation of the connecting wires.

Disconnect the wires to the rectifier & check the wiring for shorts. Check the rectifier that it passes current in one way only. In fact, each of the 4 diodes can be checked to see that they allow current to pass on only one direction.

If the rectifier is bad, replace it with one of the modern sealed type as they cost less but are more robust.

Cheers, Don.
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john
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AJS Model 14 Electrics.

Post by john »

Assuming the light weights follow the heavy weight wiring practise.

Looking at a 1958 diagram the rectifier is permanently connected to the battery but in the 1962 diagram it is switched by the ignition switch. This configuration makes the machine more tolerant to less than perfect functioning of the rectifier. So it would seem that there are two faults that once combined causes the problem. My feeling would be to get the wiring back to known standard, as then it would be easier to isolate any further faults. Again Don talks with great sense and replacing the original plate rectifier with modern sealed unit would solve the second fault.

Alan,

With both switches off most of the bikes wiring should be isolated from the battery, thus making the fault finding simpler. The multi meter test then checks for a wiring fault between the switches and the battery, or an internal fault in the battery i.e. if there is no external drain from the battery and the battery is still going flat then it is an internal fault in the battery.

John what was the current record on the multi meter?

Hope this helps

John T
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AJS Model 14 Electrics.

Post by Biscuit »

Sorry John, your original statement didn't make sense, your latter explanation added further information to it, ie. 'if the battery is still going flat'



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Merlin
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AJS Model 14 Electrics.

Post by Merlin »

Alan what shape should it beDo you mean discharged
Chemists do it with test tubes
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