Talk Morgan Forums Morgan Sports Cars Morgan Three Wheeler & Super 3 Rectifier and Compensator Failure

I was driving my 2012 M3W to have its annual service and MOT when it stopped dead with a complete electrical failure.
An excellent AA man arrived and diagnosed that the battery was not charging. He quickly charged it up and followed me for 90 minutes to the Morgan dealership with out further mishap
I have now been told that the compensator had failed and this caused the rectifier to also stop working
The cost of replacing these is nearly £3,000 which has shocked me as the vehicle is garaged and has only 3,500 miles on the cloak
Does this seem right and should I complain to Morgan?

I don't know anything at all about the M3W but you have my utmost sympathy that is a big bill for so little mileage, almost a £1 a mile..

Always worth an email to the factory with so little mileage on it I would have thought, good luck.

From what I've seen lately on compensators, Harley style, which yours probably still has with it being a '12 and only 3500 miles, I bet the comp crank nut has loosened up and the splines in the rotor have stripped out and it's spinning. This would be a bad thing...

The new Centa comes with the new rotor as well as all the goodies to get rid of the Harley style compensator. This is a good thing... Phil should probably be contacted about his urethane pucks, but I've also read here that the "new" Centas have new and improved rubber rods that hold up better. But Phil's style probably give a better clutch feel as well as improve drivability to some degree.

The new alternator rotors are held in with flat head bolts and the Centa has a LOT LONGER splined hub on the crankshaft.

Good luck and sorry this happened, but even more so just before the Holidays etc.

For the life of me I cannot see how a compensator has anything to do with a rectifier. The components of the charging system are the rotor, stator and the rectifier. Any of those can fail. The rectifier is the easiest to replace as if is external to the engine. The rotor and stator are in the lower have of the engine and, unfortunately, between the engine and the compensator, so the engine must be pulled to replace them.

First step. Unhook the rectifier. Now check the voltage between the wires coming out of the engine (not to ground). You will need to look up what the voltage should be. If it meets spec it is not the rotor/stator but the rectifier. The cost of a rectifier is about $150 or so and it is plug and play.

Dan posted as I was writing up mine. Yes, you could have an older HD compensator and the way Morgan hooked them lead to premature failure. But the good news is probably the rectifier is good, it is just the striped out splines are not allowing the rotor to, well... rotate

But think of it this way.... you now can learn some basics of motorcycle engine repair.

I can't imagine the compensator has failed as you would either have no drive or nasty noises when you do.
The symptoms are of a failed rectifier only. A common problem on the early cars due to vibration and poor earthing, most people with early cars change to a Harley Davidson rectifier which is a plug and play replacement for the CE unit, is more reliable and about a quarter of the price. Search TM for the part number or the Morgan Three Wheeler Club site for the alternative parts list.

If it were the compensator you wouldn't have been able to drive 90 mins to the dealer without a very obvious rattle at idle and low revs.

It's almost certainly the rectifier and as Rog says, replace with the Harley style unit.

Also check the battery, the standard Banner unit is not sealed for life and needs topping up with distilled water from time to time and will only last a few years anyway.

Again there are better ones listed in the Alternative Parts List:

https://www.mtwc.co.uk/wp-content/uploads/2018/09/M3W-part-numbers-V2-Word-200918.pdf

As per Rog and Chris, my comp. nut came loose and stripped the splines off the rotor but it never stopped charging.

Gentlemen
Thank you for your speedy and detailed responses
This was my first breakdown and the engine was running as sweetly as ever after the AA man got me going again
As you may guess I am not an engineer but I will pass your observations onto the dealership where I bought the M3W and who lsold me my first Morgan Plus 4 4 seater in 1968

I understood the alternator rotor is a passive device just supplying a rotating field from its permanent magnet and so inducing current into the surrounding stator from which power is drawn. I would therefore consider the likelihood of a disintegrating early HD style cush drive (refuse to call it a compensator) throwing debris by centrifugal force into the fragile windings of the stator.

This may offer a better explanation of why a cush drive issue affects charging.