Talk Morgan Forums Morgan Sports Cars Morgan Three Wheeler & Super 3 Dead Rectifier - or NOT?!

Hi all,

I had an email from Mark Evans yesterday and whilst I don't want to put it all up without his permission, there is one point which I hope he won't mind me sharing and is relevant to this thread:

"Rectifier; Our dealer network has been instructed to carry out modification of the wiring for the rectifier, we have had no issues with vehicles have had this upgrade carried out. This is covered under Warranty"

I guess this doesn't solve the bobbin shearing problem though. Do the latest cars still have bobbins for the rectifier?

Don't know about the latest but I've mounted the H-D unit on the plate without the bobbins. Over 11,000 miles on that unit without a hint of any problem.

I have 'fixed' my own rectifier-bobbin problem by simply using an additional cable-tie around the unit to prevent the heavy rectifier from jabbing around too much with the growing vibration. My first mounting failure was at 900 miles, but with this cable-tie approach, it has been bobbin-tastic for the subsequent 4,400, which is good.

Excellent solution, thanks, i'll get the tie wraps out when i get home. Until i move the rectifier off the engine and onto the chassis in the winter.

Nice fix.

Does anyone know what this mod to the wiring is ?

Ringa,

That's interesting, the cable tie is effectively fixing the rectifier slightly more rigidly to the chassis, rather than allowing the bobbins to absorb all the vibrations (I guess?).

Atalante also said he has removed the bobbins all together (simply fixing it in the original position without bobbins I presume?) and experienced no issues.

Combined with your original post, I'm starting to think you're right: the reason for rectifier failures is more linked to stress fatigue on the wires than failure of the actual part.

Maybe the bobbins aren't needed? Or would that invalidate the warranty?

I do like your cable tie solution though!

Another comment on the rectifier:

I had a rectifier bobbin shear off on my recent trip to France. Luckily I noticed it in time and was able to switch for a spare bobbin which my dealer had already provided me with.

What I noticed when doing the swap was:

- you can't just switch one bobbin. You have to undo all three
- they are attached with nyloc nuts
- nylocs are not supposed to be reused... so ideally you should replace the two which are "ok"

- The bobbin bolt isn't actually long enough - if memory serves, two of the three bobbin bolts pass through an extra thickness of metal (see the end of my thumb in the picture below) which means that the nylon part of the nyloc isn't actually (or is just barely) engaging...

Another reason to get rid of the bobbins all together?

All valid points Mr Vspec - I'm not convinced the bobbins are needed for the rectifier either and indeed HD replacement unit users also report no problems when solidly mounted.

Anyone know why these bike engines need such a mahoosive rectifier anyway? Cars have them build neatly into the alternator and they can be very small indeed. Do we really need a kilogram of electrical gubbins to control a relatively weedy 38amp output?

The bigger Cycle Electric rectifier supplied as stock on the M3W are supposed to have a feature that lets them adjust the voltage to the load. I think it was this 'feature' that caused a certain amount of failures. They are known as being on the delicate side. Whether that is electrical or mechanical is a good question.

The H-D unit doesn't use that system. It is a brute force rectifier that is always cranking out at 100% and any voltage not needed is just dumped to ground. It weighs less and has a thinner profile. Me like.