Wassell Power Unit

[bikerbob]

Hi there
I have a problem with my BSA A65 Star 1963. Just recently restored only done about 100miles went out the other day everything appeared okay had the headlight on after about 10 miles noticed that the ampmeter showing about6amp discharge, switched the lights off ampmeter showing zero no charge. Came home and after the bike had stood in the garage for about 30 minutes started the bike and now showing a good charge also a good charge with the headlights on. Next day took bike out of garage started okay showing a good charge with headlight on went for a run after 4 miles now showing discharge about 6amps came home left for about 1 hour but when started not showing a charge at all. Have checked all connections the power unit is mounted out in the open where the zener diode used to be. Battery shows 12.4 volts with voltmeter when started shows 12.08 volts. Without engine running headlight on ampmeter shows 3amp discharge with engine running shows 6amp discharge. Questions how do you test the power module and do you think that is the problem. Bike is 12v with Pazon electronic ignition with a Wassell  Power Unit replacing the Zener Diode and Rectifier. Thankyou.

[Welsh Wizard]

have you tried cleaning all the joints in the electrical circuit and before putting back together smear some petroleum jelly on each joint and tried again, some times dry joints can cause problems, so worth a check before worrying about more expensive components.

[Revband]

These units have been known to break down when hot and recover when cooled down, you could try a can of aerosol freezer, when the unit stops charging keep the engine running and spray the unit with the freezer if charging is restored the unit is faulty.

[bikerbob]

Hi there
Thanks for your replies it seems that the problem was the alternator have fitted a new one and everything appears okay I had heard that some Wassel power units had failed and I had replaced it with a different make but the problem still persisted so I replaced the alternator and as I say things are now ok.

[rogerwilko]

Please explain what was wrong with the alternator? These rarily just stop working, unless a wire was broken which is repairable usually?

[bikerbob]

Hi there
What can I say the symptons were as I described in my original post the old alternator looked okay but everything is encapsulated so something must have broken down inside, the wires leading from it were okay but I did a test that was described on another site which was connect a multimeter to both wires switch the meter to AC then start the bike and you should get a voltage reading 32 volts with slightly increased revs. Needless to say mine gave no reading at all also another test I was given was to connect a headlight bulb to the alternator then start up and the bulb should glow very bright but again nothing so I fitted a new alternator and now everything is okay.

[rogerwilko]

I'm convinced! Unusual though!