Morris Minor Owners Club

Thank you all for your comments

As a general querry I didnt realise I would get so much feedback,so apologises for posting in the wrong area. Have now ordered new Regulator and Dynamo. Will keep you posted.

I would like to second (or is that fifth) the advise to take the dynamo off and inspect the brushes- as being the main wearing part these are most likely to be the culprit.

Replacements are only a few quid and easy to fit, and the old Haynes manual reccomends checking the brushes every 12000 miles or so, so its a service item!

Every 12,00 miles?? I would have thought more like every 50,000.

Easy way to check dynamo is to apply 12volts to field and run the engine. Should get a good output of at least 15 volts if it's not sinking into a battery. I have run my car like this in the past - on night rallies - to force maximum output from the poor old dynamo. It gets a 'bit hot' though - and if done without a good load (ie all lights on, both dip and main beam + auxiliary lights) then it fries the battery !

Well, if things are working properly regulator wise then 12v should be applied to the field windings from terminal 'F' (with the ignition on) which is why it's always a good idea to check this out when performing diagnostics.

The regulator does it's job by flicking on and off thus varying the average voltage to the field coils. Putting full voltage to the field constantly forces full output regardless of need ! Of course - if there is no load the voltage can then go higher than normal causing ultra bright lights for a short time - until they blow !