Commando charging fault

Hello Jem

Yes, Bremen was very good. There were a few bikes there with charging problems; I spent time with Brian Harriss fixing his. A common issue, I think, is corrosion of the various bullet connectors resulting in additional resistance in the circuits. They need WD40 once a year and removing/reinserting. Firstly, check your alternator connectors coming from behind the chaincase for evidence of corrosion/heating.

When you say twin zenor diodes it implies that you have fitted a three phase alternator stator. If you have then find the three yellow output wires (mine are yellow) and clip a 12v bulb across any two. Run the engine to 1500 RPM only (much more will blow the bulb) and the bulb should glow - this means that phase is working. Run the same test on the other two combinations of the yellow wires. The three phases are wired as a triangle and the yellow wires come from the three points. This has been in Rh and recently described by Al Oz.A small DVM will be helpful to confirm that each of the yellow wires is insulated from earth (better than 1000 ohms).

If the three wires test out OK then any fault is with the zenor/rectifier/cabling and you are in 'complicated test territory'. Speak to Al Oz and I recommend that you fit one of his three phase regulators (about £40 or so) in place of the zenor/rectifier. Other people supply them as well but Al is good to talk to about how to go about it. They work much better than the Boyer Powerbox that has, in my opinion, too low a charge voltage. Also, fit one of Al's battery status multi-colour LEDs in place of the headlamp charging light and you will enjoy instant feedback on the battery status and charge.

80% probability it is degraded cabling, 15% the zenor/rectifier, and 5% it is the stator windings!

Norm.

My money goes on a winding in the stator calling it a day. But might be just a bad connection or broken wire from the stator.Easy to check out as Norman says above.

Dump all the Zenor diodes and associated chunks and go for a 3 phase regulator. The Boyer boxes do not have the best of reputations compared to A1 Reg boxes so check alternatives. Al Oz will be able to supply all the bits you might need. A 3 phase Stator is around £90 from him, including taxes and P&P.

Jem

Apologies for typing above before brain was fully engaged. I am in error saying that twin zenors means you have a three phase alternator - you should still have a two wire alternator because all three phase setups (I think) use a powerbox or regulator.

Norm

'you should still have a two wire alternator because all three phase setups (I think) use a powerbox or regulator.'

I think the above is likely to have Al Oz leaping up and down and about to shout rude comments at somebody very soon.

Attachment shows chunk used to sort out DC from AC provided by an early Commando 3 phase alternator set-up. Somewhere underneath are 2 Zenors. No Power Boxes here. Just some old fashioned soldering of diodes to heat sinks. You can still buy a version of this dinosaur but when you add in the purchase of a couple of Zenors it becomes more cost effective to get a modern electronic gizmo to do the job.

Phil had it sussed even without looking, good idea to check wiring connections before getting all excited about new electricals..........

I have to agree with Phil here. I have 3 wires coming from the alternator: Green. Green/Yellow. White/Green. My notes tell me it is a 3 phase alternator (though I have not looked for the receipt but I bought it 18 years ago). And whilst my rectifier is not identical to that in Phil's photo it is rather similar (just with more plates).

I brought a super-dooper Fluke DMM home from work (which can probably integrate from first principles if I let it) so I'm sure that armed with that and a few spanners I'll be able to test out the various components and electric string that once joined it all together.

What I think is great is that by typing a few words here I get all this advice from the lovely people in the NOC! And just before the Bank Holiday weekend when I have plenty of time to play! Cool or what? Ash Cutler has even offered to ride over here in the morning and let me remove the rectifier and zenors from his bike as they are now redundant after he fitted an Al Oz Power Box. I'll probably fit one of these myself but I've got to determine the root cause first (like all good Quality Engineers should).

Three phase power box is the best bet, . My Norton Manxman is now 12v on a 100 watt and a power box fitted up the front of the frame so there is a good air flow around it, but all works well , for me, Yours Anna J

Hello Jem,

I had a number of electrical issues with various Commando's over the years resulting in either a flat or boiled battery, neither of which are very helpfull when riding the Autobahn with a flying Audi up yer chuff! If your alternator is working ok ( check the wires near the stator as these break often and are almost impossible to repair) I would next look long and hard at the zenor diodes. I have had many of these litlle buggers fail on me, one brand new from a reputable dealer who was very reluctant to exchange/reimburse me for the item. Eventually I gave up and fitted a soilid state rectifier and have never had another electrical problem since! The only other useful tip I can offer you is to use uninsulated bullets that you crimp yourself (buy the right tool!) and solder and crimp the terminals! Joe Lucas-Prince of Darkness!

Regards,

Pete Austin

I fear that Al Oz must be pulling his hair outandwondering what words of wisdom are going to appear next in this thread.

I would next look long and hard at the zenor diodes. I have had many of these litlle buggers fail on me, one brand new from a reputable dealer who was very reluctant to exchange/reimburse me for the item. Eventually I gave up and fitted a soilid state rectifier and have never had another electrical problem since!

Most bike owners would agree with the first chunk of the above text but................solid state rectifiers do not have zenor diodes inside them. Do you actually mean a regulator rather than rectifier.?