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MG MGA - voltage regulator problem: help

Hi folks. The battery in my MGA went dead, so I recharged it, and over several days, it gradually went dead again. The fan belt is relatively tight. The ignition warning light was behaving correctly. The warninglight went out at anything more than an idle, and glowed dimly at idle. I thought the regulator points might be dirty, and causing the charging problem, so I took some very fine wet/dry sandpaper, and gently ran the paper through 3 sets of contacts inside the voltage regulator. At one point, two of the contacts "connected" for an instant as evidenced by a tiny spark at the contacts. Now my ignition warning light is staying on constantly! It wasn't before I "cleaned" the contacts. I tried "polarizing" the generator, but my ignition light still stays on. Have I toasted my voltage regulator, or is there a simple solution/fix? If the regulator is toasted, where in Ontario Canada can I purchase a new (or good used) 1600 voltage regulator (the one with spade connectors and NOT screws) Thanks! GLenn
Glenn

<<<snip>>>
Have I toasted my voltage regulator
<<<snip>>>
Possibly. There are two bobbins in the regulator: one to regulate the charging, and one is a cutout used to keep the battery from discharging when the engine is shut off. It is supposed to open when the dynamo's output is less than battery voltage.

My guess on the initial problem is the cutout was sticking shut and the battery was discharging through the field windings of the dynamo. A check would have been to disconnect the SMALLER (F terminal or yellow-green) wire at the dynamo. Then connect a voltmeter between the wire and ground. Any reading other than zero indicates the cutout isn't operating correctly and the battery is discharging through the field windings.

Blake
Bullwinkle

Glenn,

Had similar problem with my regulator, at least your initial problem. No charge but light behaved fine.

Cutout was stuck.

Take the cover off the regulator. You should be able to see the cutout operate as you increase the revs above idle.

Chris.
Chris C

It is possible that you have fried the regulator, but possibly the contacts just need to be cleaned again. You should never use sandpaper to clean electrical contacts. The particles on sandpaper are non-conductive and can become embedded in the contacts preventing them from closing. To clean contacts properly, you need a burnishing tool. In a pinch, you could lightly use a very fine file, but you don't want to remove any metal, just the surface crud. It is also possible to fry the regulator or the wiring by manually closing the contacts, so you should always disconnect the battery before cleaning.
Jeff Schultz

You can also fry the generator by manually closing contacts in the regulator. If cleaning the contacts doesn't change anything, here is a good step-by-step procedure for diagnosing the entire charging system. http://www.vintagemg.com/ArticlePDFs/Tech103.pdf

Jeff Schultz

Glen - Before cleaning the regulator again, disconnect the battery. Closing the cutout contacts with the battery connected and the engine not running, can cause the contacts to weld together and then burn out the field windings in the generator. If you find that the regulator is bad using the troubleshooting guide that Jeff linked, you can get a solid state regulator built into the original housing by contacting Bob Jeffers at bobj20@adelphia.net. Bob makes a solid state regulator, fits it into the original housing and adjusts it to match the generator that it is being used with for about $80. Good luck - Dave
David DuBois

This thread was discussed on 29/06/2005

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