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MG Midget and Sprite Technical - generator smoke

I have been trying to help get my friends 67 sprite back on the road after sitting for several years. I was sorting out the carbs when the new electric fuel pump and starter stopped working. I noticed smoke coming from the front of the generator and also the brown/yellow wire connected at the back smoking. I quickly disconnected the negative cable to the battery. I let things cool down and then tried connecting the battery again. I had some sparks at the battery terminal and then, very quickly smoke again at the same locations. What went wrong? Generator, regulator?Short somewhere else?
B Stone

Ah Lucas
I reckon the headlights are full---
If you have let 'all' the smoke out you can get replacement smoke----------lol

Sorry

I suspect the generator bushes are that badly worn that it has shorted out inside, unless that brown/yellow wire is shorted to the body somewhere-
You could try disconnecting the brown/yellow from the rear of the generator and see if you still get a spark when connecting the battery
No spark--definately a generator problem
Still sparks--brn/yel shorted or regulator issue---regulators can die from just sitting from corroded contacts etc.
You could also loosen the drive belt and try/see if there is excessive movement in the pulley/bushes
William Revit

I bet the regulator points are stuck and the battery is shorting through the dynamo. Willy's tests will verify this.
Bill Bretherton

Thanks for the help will check it out.
B Stone

The Willy test indicates a generator issue. Waiting for a call from the shop to get an update. I would like to continue trying to do some tuning, while waiting for the gen. repair. Can I run the car without the gen. hooked up without damaging anything ie. coil,points, regulator etc. as long as I don't overheat it?
B Stone

Shop says $400.00 to rebuild generator on 1962 Sprite. Have been reading threads for converting to an Alternator. Two questions , which alternator is the easiest fit and what about the Tach. drive connection?
B Stone

Mo$$ sells a new one (part number 140-200) for$119.99 or a rebuilt one (part number 540-200) for 409.99 but that includes a $275.00 refundable core charge. You could try Little British Car Company which is a Moss distributer and charges about 15% less.
Martin

Thanks, I am familiar with both and have spent plenty with both on my own cars. Will probably go that route.
B Stone

Not sure if the dynamo (generator) Lucas 'Smoke' is the same as the smoke for the wiring loom referred to above, but if so looks like it was available for sale in the USA: http://www3.telus.net/bc_triumph_registry/smoke.htm

Cheers
Mike

PS I did get a great dynamo and voltage regulator rebuild done recently.
M Wood

You can get an an aftermarket alternator that looks like a dynamo casing which also has the rear take off point for an early rear drive tacho:
See the 'Dynamator' product for Lucas C39 Dynamo replacement: http://bbclassics.co.uk/electrical-accessories.html

If you do want to rebuild your Dynamo see:
http://midgetandspriteclub.com/wp-content/uploads/2016/06/C39_dynamo.pdf

Cheers
Mike
M Wood

The Alternator from BB Classics is a good quality product - I have used these for about the last five years and have fitted them to quite a few cars. None have been a problem to fit, and the version with the rear tacho takeoff is also very well executed
Dominic Clancy

Received the rebuilt generator from Moss. No markings that it's Lucas expect for the box and no provision to hook up tach. drive. My core is original Lucas with a threaded end for the Tach. What do I do to get a Tach? change to something else? The guys converting to Alternators must have same issue.
B Stone

Did you not order the one with the tach drive?
Dave O'Neill 2

If you ordered it to suit your car it should have it-----------send it back and tell them to send the correct one, they should know better than that
William Revit

If the brushes are worn out and shorting at the dynamo armature, they are very easy to replace. I always carried a set and had to replace them on the road one night driving across Arizona in the snow. Just remove the generator, unscrew the two long bolts and pull the back off. You will see if the brushes are worn and dangling or if they are still viable.

Repairing a Lucas generator, as long as the field coil is intact, is very simple and it will go around again and again just by replacing brushes and occasionally the front bearing.
Glenn Mallory

brushes looked fine, armature looked okay. Nothing burnt or melted that I could see and field look good. I think the shop is just not used to working on these. Going to get another shop to look at it.
B Stone

If you put it back together and get them to run it up on their bench and see if it charges
With both terminals joined together it should have unregulated charging so don't spin it too fast, just creep it up and see if it goes over 14v at a reasoably slow speed--If it does it's ok---problem is going to be in the reg.
willy

I'm still concerned that there was no sign of where the smoke came from
Did they have a growler to test the armature
William Revit

Does it make any sense to put an inline fuse between the regulator and the brown/yellow wire in case of a failure with regulator or generator? I have to cut back the damaged wire anyway.
B Stone

This thread was discussed between 30/07/2019 and 18/08/2019

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