Cross wiring bikes to check charging system.

[jj.palmer]

Hi,
The charging system on my KH500 is not working, I suspect the dynamo.
I am proposing to cross wire the KH500 to my NH350 and therefore by running the NH350 it would check the rest of the system ie wiring, control box etc, other than the dynamo of the KH500. Both bikes are 6 volt and the charging system on the NH350 is working ok.
The way of cross wiring is shown in the attached diagram, not being too good on the electrical side I would appreciate if those who are would tell me whether I am doing anyting wrong.
Sorry about the diagram being on its side I cannot get it the rightway up.
Your help is much appreciated.

Regards
john Palmer.

[simon.holyfield]

Assuming the ammeter wiring is still in place, the one thing that you haven't shown is the KH regulator earth. If that's in place, effectively earthing the two bikes together, it's a sound approach.

They are both positive earth, right?

[Steven.Carter]

Providing the wires are long enough I see no problem. I'll ride one of the bikes for you if that helps

Steve

[jj.palmer]

Thanks, the 2 bikes are both +ve earth and the KH500 control box connection E is still to earth and connection A is still to the ammeter and hence on to the battery.
By cross wiring in this way I thought it would save me interchanging individual parts ie control box etc. from the KH500 to the NH350 to isolate were the problem is, it would also check the KH500 wiring for any poor/wrong connectons.
I will come back and let you know how I went on.

Regards
John P.

[admin]

Your test only validates the dynamo output - i.e. just routes in the NH dynamo which is a known good one.
It doesn't validate the regulator or wiring.

You can achieve exactly the same results by just connecting the D & F together on the KH dynamo, in situ, and then connect a 12v bulb with that to earth.
start the bike. No light = no dynamo output

testbulb.jpg (8.62 KiB) Viewed 4151 times

Doing it this way also gives you an opportunity to re-flash the field coil, clean up the armature and brushes and keep retesting.
All of these things you can do with the dynamo in situ.

[jj.palmer]

I have now cross wired the two bikes as proposed and it has proved the charging system on the KH500, other than the dynamo, is in good working order, the ammeter, cutout/regulator and wiring all worked fine.

John- admin, I have never run the bike before but I did know that the dynamo was not charging as I had done the tests that you prescribed, I therefore did not want to go and get the dynamo repaired and then find something else within the charging system was not working. I can now feel assured that once I have got the dynamo working all will be fine.

Next job is to strip the dynamo and more than likely I will be back for more help.

Now where is that long peice of wiring, Derbyshire to Hampshire, Hmmmmmmm.

Regards,
John P.

[paul.jameson]

I had difficulty persuading the dynamo on my newly rebuilt Square Four to charge, despite all the usual tests. Eventually, I ran some fine wet-and-dry paper over the (new) commutator. It has charged perfectly ever since.

[nevhunter]

A newly assembled dynamo may not start charging due to losing it's residual magnetism. Flash it with a battery with the correct polarity and it should be OK straight away if it's all serviceable. Sometimes I just close the cutout points momentarily but beware of them occasionally welding closed . Separate straight away if this happens. Nev

[jj.palmer]

Could someone please confirm which of the two cables coming out of the dynamo field windings goes to the terminal "F" and which goes to the earthing screw. One of the cables has a small sleave around it.

On my NH350 the sleaved cable goes to terminal "F" but I am fairly sure that when I originally stripped the KH500 dynamo the sleaved cable went to the earthing screw, now confused.

Regards
John P.

[paul.jameson]

The field cables can be connected either way round but one way gives you a positive earth dynamo and the other way gives you a negative earth one. If you connect F and D on the dynamo together, then connect them to one terminal of the battery with earth to the other terminal, observe which way the dynamo rotates. If it goes the same way as your dynamo is driven by the bike, you have the field terminals the right way round. If it goes the other way, swop the field terminals over and it should go the correct way.