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MG MGA - charging system HELP

A couple of months ago I was having charging system problems. Did the tests everyone suggested. I replaced the voltage regulator. I was still having problems. Took the generator and volt. reg. in to be tested. Came back OK. Installed it and it seemed fine for 5 min. then the light came on again. So I polorized the gen and the light went out. 5 min later the light came back on so I repolorized the gen. and the light went out.
Why wont't it hold????
What the heck is going on.
HELP
Thanks
Kris
Kris Sorensen

Hi Kris. It is quite usual for the charging light to come on when the engine is idling at slow speed. If the engine speed increases, the charging light usually goes out (in most cases) It is not entirely unheard of for the charging light to remain partially (dimly) lit, even at higher engine speeds. I am therefore wondering if you actually have a charging problem or not? Does your car ever crank slowly, or refuse to crank, even after driving for long periods of time? If not, then perhaps you don't actually have a charging problem. If yes, then you might want to check these items, if you haven't already: Is your fan belt properly tensioned? Not too tight, but not too loose? Is your battery able to hold a charge in all cells? A battery with only one marginal or dead cell wont reliably hold a charge, or will hold it intermittently. Have you had the battery tested? Are your battery terminals spotlessly clean? Are all your battery ground connections bright and clean? IS the engine motor mount to body ground cable clean and in place? You might want to check the long battery cable running from the battery to the starter pull switch for loose terminals or dirty connections. If your generator and regulator were checked by a competent mechanic, and come back good, then the problem is likely due to a bad battery or faulty wiring, or as mentioned earlier, perhaps there actually is no problem. To do a rough check on the charging system, start the engine, let it idle and then remove one battery terminal. If the engine immediately quits, there is a definite problem with the charging system. If the engine keeps running, it is running only on power from the generator/regulator, and indicates that these components are at least working, though they may be out of adjustment (incorrect voltage or current levels) Hope this helps. Glenn
Cheers! Glenn
Glenn

I would agree with Glen on everything but the fan belt tension. Generators do not produce the drag that an alternator does when operating and as a result are not prone to loose belt problems like alternators are. Generators on the T series cars, MGA and the early MGB (Lucas generators) are prone to damage by tight fan belts. The generators use a porous brass bushing at the rear end (commutator end) and a tight fan belt causes an excessive amount of wear on that bushing. The problem is that the wear is not noticed until the generator starts making a squeaking noise from the armature rubbing against one of the pole pieces inside the housing (see my article on belt tension at: http://www.omgtr.ca/technical/tdtf_fan_belt/loosen_up.htm)
The other thing is the grounds, as Glen says, clean, bright metal at each ground point. I would add that you should then coat the clean metal with some sort of conductive grease such as KoperShield (again see my article on ground point preparation at: http://www.omgtr.ca/technical/General%20Technical/grounding.htm)
Finally, check the voltage at the battery terminals when the car is running at a fast idle. It would rear around 13.5V - 14.5V if the generator/regulator are doing their job. If your idle is set very low (below around 800rpm the ignition light is going to come on. For a good description on how the ignition light works go to Paul Hunt’s web site, pages of Bee and Vee at: http://www.mgb-stuff.org.uk/ , click on Spanners, then on electrics and then on alternator/dynamo. Scroll down to the section of the dynamos for the description of the ignition light operation. Good luck - Dave
David DuBois

This thread was discussed on 19/12/2004

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