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MG MGB Technical - Voltage Regulator Hesitates?

Hi All,

1963 MGB. New generator, polarized, and tested according to John Twist video, so I know it's functioning properly. Start up and charging light goes out, but sometimes it glows dimly until I blip the throttle, then the charging light snaps off as if a switch was turned (and stays off). Then, turn on headlights and charging light starts glowing dimly again, until throttle is blipped and the charging light turns off sharply again (and stays off). Then I can turn on the heater fan, high beams, wipers, etc. and the charging light stays dark, and I can drive around without draining the batteries.

The voltage regulator is a replacement (non-Lucas) unit from Moss. I suspect the contacts are not opening/closing at the right times.

I also looked at Moss's on-line literature for the older regulators (MGA and earlier) and the contacts must be cleaned and adjusted before use, but there are no such instructions for the MGB control box.

I wonder if I should at least just clean the contacts? I would be pretty clueless trying to make any adjustments!

Any thoughts?

Cheers,
Greg
Greg Van Hook

So whats the problem....I'd leave it alone!
Michael Beswick

Sounds normal to me. A dynamo/generator usually *doesn't* supply enough charge at idle to keep the warning light off, so it's normal to see it flicker or come on, especially if you start switching electrical loads on. It's *alternators* that should keep the light off at idle, once it has gone off, and no matter what is switched on.
Paul Hunt 2010

Thanks guys. After 14 months of fighting cooling and charging issues, I appreciate your answers!

Greg
Greg Van Hook

Greg - You might want to consider sending the regulator to Bob Jeffers bobj50@comcast.net for conversion to solid state. See the articles, Voltage Regulators 101 and Solid State Voltage Regulator Conversion in the other Tech Articles section of my web site at: http://homepages.donobi.net/sufuelpumps/ Cheers - Dave
David DuBois

Hey Dave, how the heck are you? I just emailed Bob Jeffers. Is he the same person who converted the clock on my TF?

Greg
Greg Van Hook

Greg - I'm fine, just trying to work myself to death between fuel pumps, building a shed on the side of our carport and caring for my 88 year old mother who just had hip replacement surgery (fortunately, my wife is handling most of the later). How is everything with you?

Bob Jeffers just does voltage regulators. You probably sent you clock to Hal Kramer. Both are members of the NEMGTR. Cheers - Dave
David DuBois

Just measured the voltage at 3,000 rpm at the solenoid hot wire. 13.00 volts, then 12.78 volts when headlights switched on. Hmmm, batteries barely getting a charge.

Hi Dave, just livin' life (staying away from log splitters), and Alex is looking at colleges. Alex just did the Long Branch (New Jersey) Half Marathon in his power chair for Cure CMD (Congenital Muscular Dystrophy), his condition and a group we're heavily involved with. We raised $22,000 for research. Sorry for the non-MG plug here, everybody!!!
Greg Van Hook

Greg, what is the engine ticking over at? I think I might wind it up a couple of hundred.

Colin
Colin Parkinson

Small world, I was born in Long Branch. RAY
rjm RAY

Colin, OK. Think I can get it up to 14.5 V with some more revs?

My next step is to check the voltage regulator. That's done at 3,000 RPM (according to the Lucas Fault Diagnosis Manual), so I thought 3,000 RPM might be a good number.

Greg
Greg Van Hook

3000rpm is correct, it should be outputting 14.7v to 15.3v at 20C/68F with a charged battery and minimal load, slightly higher than that at lower temperatures. Your voltages are indeed way down.

Do a no load test by disconnecting the wiring from the dynamo, linking the D an F terminals, with a voltmeter between the link and the dynamo body. Start the engine, and slooowly increase the revs watching the voltmeter. Don't exceed 20v, and you should be getting close to that by 1000rpm, steady voltage with no fluctuations. Fluctuations could be worn brushes, dirty comm, damaged windings, all of which will cause low output voltage.

If that's OK the problem could be regulator adjustment, dirty contacts, or bad connections anywhere from dynamo to solenoid.
Paul Hunt 2010

Thanks a lot Paul. Will do that tonight.
Greg Van Hook

Well, Paul, I never thought I could do it, but the charging system is all good.

After John Twist's video and then your dynamo test, I was certain that the dynamo was good, and the only culprit was the control box.

The voltage check at the control box according to the Lucas Fault Diagnosis manual showed about 13 volts. I adjusted the cam on the "D" coil and now I'm getting the 14.5 - 15.5 volts I need.

Either that or some intermittent thing re-connected...........
Greg Van Hook

This thread was discussed between 17/05/2010 and 20/05/2010

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