Both my Ruby and Special have auto-advance distributors. The Ruby shows about 2amps discharge when the ignition is switched on and the points closed. However, the Special shows about minus 15amps. (Always has done since I got it about three years ago, it's only now I am trying to do something about it!) Both ammeters show a normal 2-4 amp charge with the engine running - but the Special's battery runs down over a month or two despite some good long journeys and quickly becomes reluctant to turn the starter motor other than sluggishly. Has anyone got ideas about why the Special shows this large discharge and where I should start looking? Nick

Nick

Seems strange that when the engine is running you have roughly the same charge?
If there was a short or problem of some kind with the specials wiring you would think that this current would be subtracted from the net result and when running you would still show either a discharge or less positive charge (unless the 3rd brush has been wound up to compensate)?
Just to prove you are not going mad how about temporarily hot wiring it? You could run a cable to the coil (disconect the ign feed) from the battery with an ammeter in series and see what current flows, if both cars agree roughly then your problem is not in the coil or dizzy, but with the wiring or something else which you can methodically work through to trace it?

good Luck

Steve

Do both have stop lights? ignition on .not running .hand brake on. will show a bigger discharge. let off the hand brake and see..

Hello Nick,

I wonder what current the sysrtem draws with the igntion on and engine stationary but with the contact breaker "open" (maybe push a piece of card or something between the points or else lift the lead off the LT terminal on the Distributor)

I will be amazed if your fault has anything to do with the coil and distributor itself, as I can't conceive how the engine would run OK if there was a fault in these components which would allow such a heavy "fault current" but still enable the engine to run.

I think you must have a drain on the main suppy system somewhere.

What sort of ignition switch do you have?

The best way of isolating the problem is to make a study of the wiring diagram and progressively "lift" the wires going to each circuit group ( lights etc) until the current draw dissapears.

An extra 13 or so amps seems awfully like lamps, but it could be any one of a number of items.

Kindest regards

Barry R

Steve, Mac, Barry, thanks for your thoughts to date. I will post a full reply later but from what I have checked so far the problem remains irritatingly obscure!

Nick

Just taken Steve's advice and hot wired the coil having removed the ignition connection to it. Result? Hurrah. A one amp drain before starting up and a 10amp charge when running. (Yes, I am shifting the third brush back!) So now going to check wiring on the ignition switch and if that doesn't reveal anything I'll try a substitute switch. Will post result in due course. Thanks guys. Nick