MG T-ABC

Charging systems are not my forte. Recently put a new battery in a 1936 MG TA. In the dark, managed to install the battery cables backwards. Upon making the connection, there was a loud "pop" noise like something electrical just shorted out. The ignition was off at the time and the vehicle was not running.

The battery was then installed with the correct polarity. The car starts, runs and drives fine, but the ignition/red light stays on. I assume this means the charging system is not working? However, by checking voltage output from the dynamo, it appears that it is generating about 13+ volts. Only issue is that the red ignition light remains on while the engine is running. The car is wired positive earth.

I've been told to ?polarize? the voltage regulator by (and this is primarily where I'm confused) jumping or touching (w/something like a screwdriver) one or two (??) of the terminals of the VR. That's intimidating to me, but I'm willing to try. I've also been told to replace the VR. That advice coming from someone who feels I've fried the present VR. Does that sound right? Any help would be appreciated. Thanks so much.

The voltage regulator does know know the difference. You "flash" the dynamo. You do not use a battery cable to flash the dynamo, just a little wire. The wire may come from the voltage regulator. FromTheFrameUp has a instruction sheet on their website. Here it is--
https://cdn.shopify.com/s/files/1/0270/ ... 1661302167

They talk about the F terminal. If yours are not marked, the F terminal should be the smaller diameter terminal.

You might want to look at the back of the control box. You may find that's where the pop came from and it will be obvious. There's a large resistor on the back that may have gone. If you want to have it rebuilt and calibrated, Jerry Felper is your guy. He's in Anaheim, CA so not too far away.

I don't think polarizing is going to solve your problem but it can't hurt. I hesitate to tell you how to do it because I'm not that familiar with the 3 brush generator system. If it were the same as a 2 brush system, you just connect a length of wire to the A terminal of the control box. Then quickly swipe the opposite end of The wire a couple times across the F terminal of the generator. It should make a small spark at which point you're done. Some people polarize the control box itself also, but I rarely do that. In all honesty I've rarely found it necessary to polarize the generator either. But you will get lots of different opinions on that.

Here are some resources on this site that may help:
http://www.mg-tabc.org/library/mgtatb-e ... rcuits.pdf
http://www.mg-tabc.org/library/lucas_ge ... _tests.pdf
http://www.mg-tabc.org/library/lucas_check_charging.pdf

EDIT: Duncan is quicker than I am!

The reason your IGN light is on may be that the contact points on the shunt coil in the voltage regulator may be stuck closed. Open them with a wood stick like a popsicle stick.

Hi Bob,
not any point fitted in the regulator is reposible for a lighting ING bulb.
the ING bulb is connected from ING Swith, the other side of the bulb is going to the teminal D on the regulator,
and D from regulator go to D post on the Dynamo, no points from ING Swith to the D post
of the Dynamo,
cheers Carl