Morris Minor Owners Club

Sunday started the car up, fine, went to Webbs car show and when it was time to leave the car wouldn't start, flat battery ?, so 2 nice gentlemen gave me a push and the engine only needed to turn over once and it fired up straight away, got home ( 9mls ) without a hitch. Next morning started up ok, so I left it and tried again some 6 hours later and behold it tried to turn over but couldn't make that final turn to start, So i'm thinking that there is either something draining the battery or the dynamo isn't charging when the car is running ,so could it be that when it is running and there is no charge could the engine be dragging any power straight out as well as any reserves. I don't think it could be anything to do with the starter motor as I have have tested it by turning it with a spanner and it's as free as it could be. In desperation I took the dynamo off to have a good look and there doesn't seem to be anything wrong although I haven't had it apart as yet. the brushes still have plenty of wear in them, so if anybody could point me in the right direction as to what to try next I and Mungo would be eternally grateful.
sid

First move -is/was the fan belt tight enough - and was the red IGN light going out when you revved up ? Also - check the battery terminals are nice and tight - and the earth cable that runs from one side of the battery - is it tight and corrosion-free where it is bolted to the body shell? Best check too - IS there anything that could be draining the battery - wireless/alarm extra lights - anything like that ? Get a simple Multi-meter and check the battery volts - both when it's sitting - and when the engine is revving up. Report back what you find!

everything as you have put is ok even the ignition light goes out when I start the car after first charging the battery. The only extra thing that is on the car is indicators to go with the trafficators and an ampmeter which incidently doesn't do a lot when the engine is running, it hardly moves except when I put the indicators on it shows a discharge. But tomorrow just to make sure I will go around everything again using your checklist and make sure it's ok.
sid

So - you have an ammeter ? Put on the headlights and the heater fan and the brake lights - and revup - does the ammeter show a discharge ? It should sit right in the middle, maybe a slight charge - and certainly NOT a discharge.

hiya bm, Yes when I put anything on it shows a very very small discharge but otherwise when I am driving along the needle hardly moves a at all , it more than likely stays in the middle of the gauge showing nothing. But having said all that I think I have found the problem and that is the commutator that's supposed to have grooves in it for the brushes seems to be very smooth as though it's well worn, so what I'm going to try now is to get a broken hacksaw blade and try to clean out the grooves and then see what happens. reasoning it out, if the brushes aren't doing anything to put power back to the battery then it seems to me that when it starts up all it's doing is using energy from the battery without replacing it. I'll give it a go and let you know how I get on.
cheers sid

I suggest your Control Box needs adjusting. How to check - start the engine run at good fast idle - take a wire from the non-earth side of the battery - and touch it to the small terminal on the dynamo - this will put it to FULL power - and should show a very healthy charge on the ammeter - obviously you need someone else to watch that while you do the touching! If this works - then the dynamo is fine - either adjust or replace the control box.

The commutator isn't supposed to have grooves in it.
While you have the dynamo apart wash the dust etc out of it, this is made up of copper and carbon, both are conductive, and not conducive to optimum operation.
Same thing applies to starter motors, in spades.

The dynamo comm should really have the grooves scraped out - but I honestly don't think it matters. I believe the starter comm should NOT be scraped.

hi all, after your suggestions and the process of elimination, I have finally found the solution. the last thing that I tried was the starter motor, if I left the connection off, the battery held it's charge, but when it was connected the battery went flat, so I gave the connection a good clean up with new washers and a nut, put back and tightened up everything, that was done on fri' evening and as yet everything is hunkydora. So thanks everyone for your suggestions and pointing me in the right direction.
regards MUNGO