Morris Minor Owners Club

...or at least, presumed alternator failure!

During some dramatic stop-start manoevring on a hill the other day, an unusual whine developed, coinciding with the blue light coming on. I got home, and took the alternator out.

There was a fair bit of carbon powder in there, and the brush that goes in the outer run (the one on the right in the photo) is quite worn but still in contact with the rotor.


examining the brushes on an alternator by Dru Marland, on Flickr

...I cleaned everything up and replaced them, and bench tested it - span alternator by hand, with meter across the output terminals. Utterly zero voltage. Is this an ex alternator, do you reckon?

Well - BLUE light is main beam warning - not alternator......which would normally be the RED light. Your brushes look ok - swap them over - the outer track brush always wears more. Spinning by hand will do nothing - stick it back on the car and see what happens. If you have a meter - you are looking for 13.8 volts when you rev up.

Connect it up to the cars loom before you test it or you will kill it.

whoops- sorry! RED light stays on, not blue!

sorry, Mark- I missed your reply there. Oh dear....

Well; I changed the brushes over, reassembled, and put the alternator back on.

Voltage at battery (engine off) 12.6v
Voltage at battery on fast tickover 12.1v

Voltage across terminals of alternator 9.5v

Ignition red light remains on and bright during running

...and the alternator is whining again. There is a bit of play on the rotor; I guess a bearing is about to throw its hand in, too

If it was me I'd consider converting to a dynamo - but I doubt anyone else will suggest that! (sorry)

well, call me stravagant if you like, but don't call me late for lunch. I've just ordered a new alternator from ESM.....

It does seem to be poorly - but these alternators can be repaired you know....... ESM - hmmm - won't be inexpensive..... No scrap yards in your area ???? I agree with Ray - a dynamo is very reliable and plenty of electrical power for a standard car - UNLESS doing a lot of commuting in winter when it will struggle with heater+wipers+headlamps etc in stop-go traffic......for that you DO need an alternator.

Yes, you can't beat a simple dynamo, the old ones are built like a brick toilet and can be skimmed many times, the voltage does drop after many skims as the commutator gets smaller.Of course you can always give it a boost trickle charge at night. My MM minor and morris 8 are still on there original dynamos. Keep em running.

what about a solar charger with the dynamo pretty cheap now

irmscher wrote:what about a solar charger with the dynamo pretty cheap now

This is how I keep the battery topped up at the moment, works well for me with a dynamo and a standard set up. I don't have any gadgets.

Solar chargers are still cheap!!!

http://www.maplin.co.uk/solar-powered-1 ... rger-98358

http://www.maplin.co.uk/solar-powered-1 ... ger-223251

me also, one on each car except morris 8 is 6 volts. Does any one know if you can get a 6v solar top up panel? smithskids.

The standard solar panel works perfectly well on a 6 volt battery - I use them to charge up 4.5 volt battery packs for my railway lamps. There's NO chance of overcharging ...
But solars are designed to just keep a car battery topped up when the car is not being used for some time - the charge gained (especially in winter) will be negligible on a day to day basis.

sorry to drop out of the conversation there! -just been running a narrowboat up the Severn from Bristol to Sharpness... the boat has just had solar panels added, v handy for keeping the fridge going.

...anyway, I shall tinker with the alternator some more, but I was in a hurry to get the car up and running for some journeys that need making just now. Shall examine rectifier, regulator etc at meisure after I've found out how to test them -thank you for helpful suggestions!

The standard solar panel works perfectly well on a 6 volt battery - I use them to charge up 4.5 volt battery packs for my railway lamps. There's NO chance of overcharging ...
But solars are designed to just keep a car battery topped up when the car is not being used for some time - the charge gained (especially in winter) will be negligible on a day to day basis.

Anything up to 2w panel isn't an issue for overcharging..

However if you've got a 15w panel, then it would (eventually) overcharge a large 12v truck battery, let alone a 6v battery.

I'd never really thought about using the solar panels in winter on a daily driver car* as I only use mine on cars that are laid up.. however it's not a bad idea. The panels say not to leave connected when the car is running (although they are diode protected ) but it wouldn't be hard to wire it up in a way that's disconnected when the car is running.


* I've tended to trickle charge the car overnight if it's getting discharged with high loads and no/low speed driving.

...and the alternator is whining again.

That's usually an indication of a faulty rectifier.

thank you, Katy- that is useful to know

irmscher wrote:what about a solar kits charger with the dynamo pretty cheap now

Yes solar charger are bit cheap but lot more effective..Even I am using similar set up and very much satisfied with the outcomes.