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MG MGA - Control box burn out

It's not an MGA but as the electrics are pretty much identical, I though I'd give you guys a go at this one too!

I have a midget to look at because the fully charged battery was going flat after a drive of just 10km or less. The battery has just been changed to see if that was the issue, and no improvement resulted.

Going to check and adjust the dynamo control box I discover that the left hand coil (the one with the adjusting screw) was looking decidedly sorry for itself, and a light touch with a screwdriver caused it to crumble - it is completely burnt through.

The question before I fit a replacement is : What needs to be checked and fixed before sending another one to a premature grave?
dominic clancy

A first test would be to remove both wires from the dynamo. Measure the resistance from the smaller (field) terminal to ground. It should be around 6 ohms. If you see 3 ohms one of the field coils has shorted to the case. Don't proceed if you get 3 ohms or less.
David Ahrendt

Sure you have already considered this, but is now the time for an alternator?
Graham V

X 2 what Graham said.

Unless you can get hold of an actual original-equipment BMC regulator I would forget about using a generator and fit an alternator.

You should ask Stuart Mumby how many new voltage regulators he has fitted over the last few years, I think that he has fitted at least 4!

I converted mine to alternator about 7 years ago and it has been fine.
If you follow Barneys updated wiring instructions it will be a "fit and forget" exercise.

c firth

An alternator is certainly a viable solution but if you want to maintain an original look you need the dynamo. The real problem is that the regulators available today are junk.

If you decide to ditch your offshore regulator we can provide a solid state conversion which will be very stable and reliable. I really don't want to be part of our shameless commerce division but check us out at:
David Ahrendt

I'm grateful for the replies, particularly to David for answering the question.

I have bought a replacement unit from Moss. If this burns out then I will switch to the same Accuspark alternator I have in my own car. Th reason I didn't go for that solution is that the car is still +ve earth and has an electronic tachometer that I will also have to remove and modify if I decide to go that route, plus switching the battery around, the diode on the fuel pump........

and as the Accuspark alternator has only done 5k km in my car, I'd like to see a bit more use before I start retrofitting other cars with it.
dominic clancy

This thread was discussed between 10/11/2015 and 11/11/2015

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