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MG MGA - generator light ON

My generator light is remaining on and my last run with the car totally drained the battery. This is a sudden change, within the last two weeks.

I had run the car in the last week of May without mishap. I have turned the engine over weekly in the garage without problems, until two weeks ago I noticed the generator light remaining ON. I took the car out for a run last weekend and the battery drained. I had to push start the car. Also, when I ran under load, the engine had a bit of misfire. Not usual. So, perhaps it is symptomatic of the issue.

I would appreciate any help with the diagnostic procedure on this 'malady'. I consider myself between Novice and Intermediate on charging systems.



Thanks All.

SL
Stephen Lofaro

The first thing I would do is clean the points of the regulator/cut-out.
This is described in the Workshop Manual (see attached image).


Mick


M F Anderson

Misfire is as a result of weak or missing spark because of the low battery. When the battery is recharged the misfire will disappear.
dominic clancy

Stephen - Your generator brushes may be worn out or the regulator may need some attention as Mick suggests. You can test the generator easily to see if it is the problem. See the article, Testing a Dynamo/Generator in the Other Tech Articles on my web site at: http://homepages.donobi.net/sufuelpumps/ If the generator is bad, you should be able to find a good auto electric shop in your area that can overhaul the generator - all the necessary bits and pieces (brushes, rear bushing and front bearing are available from Moss. Cheers - Dave
David DuBois

A bit obvious I know, but I presume that your fan belt is still intact?!
Lindsay Sampford

Test the generator first. Most common problem is worn brushes, a $3 fix. Any time you work on the generator, also test the regulator. A failed $40 control box can take out a $100 generator, and it can fry a replacement generator just as quick.
Barney Gaylord

I still think that you should check the regulator first. If it has poor generator brushes it would not charge, but your symptoms of the ignition light staying on and the battery apparently discharging back through the generator point to a regulator problem.


Mick
M F Anderson

Stephen,

I think there is a problem in interpreting your message post. When is the generator light on? When the engine is running or when the engine is stopped and turned off?
If the light is only on when the engine is running, the problem is probably the generator brushes.
If the light is on when the engine is stopped, and the ignition turned off, it is the regulator.


Mick
M F Anderson

This thread was discussed between 03/07/2009 and 04/07/2009

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