MG T-ABC

Drove my TC to a small classic car evening at a local pub in the UK this week (where it received much attention until a 1920's cadillac appeared .... but I digress), and drove it home late with headlights on probably for first time in years. After a few miles the ignition light came on & ammeter showed maximum discharge. Switching headlights off got ammeter closer to neutral. Checked connections & fan belt which were ok, so drove it home.

Next day I made some checks; battery good at 12.5volts, dynamo / generator output around 3 volts at 1000 rpm. Disconnected the dynamo & bridged D & F terminals, voltage fluctuated wildly extremely rapidly (I could just about read 3 volts and 19 volts but display was flashing perhaps 20 readings per second on digital meter, same at tickover up to 3000 rpm. The meter then read -1 & stayed there no matter what I do or setting, so ........

Connected a spare digital meter & same flashing display from bridged D & F terminals.

Removed dynamo & on brief inspection looks ok visually, and will power as a motor if bride D & F connections & apply power.

Seems likely I need a dynamo rebuild, but before I proceed would welcome any thoughts / experiences / further tests from other members. Also, any thoughts whether a faulty regulator could have blown the dynamo i.e. a rebuilt dynamo won't solve the problem?

Thanks

Nigel

Nigel:
I too, am interested in what you find out. How can the regulator be tested either in or out of the car to determine if it needs cleaned, adjusted, both, or thrown in the bin? Seems the problem needs to be narrowed to the dynamo, or the regulator?

Brian W.

Nigel,

The first thing I would do is try to find a old time analog voltmeter and see what you get. Just this week I was helping a friend with a charging problem on his TR3. He had a fancy digital meter that was going crazy with all the electrical noise in the TR. Using my 40+ year old analog meter showed a very steady 14.3 volts at the battery while charging. Sometimes, newer digital devices have a hard time on old electrical systems.

Once you see what voltage you really have then you can from there.

Dave

Same thing happens when I try to use a digital meter on my old cars. I think the lack of shielding on wires and components is the culprit.

Thanks for the responses folks, it didn't occur to me a part of the problem could be with my digital meters - I've now ordered an analogue meter!

Meanwhile I've had an auto electrical specialist check over both the dynamo & regulator, and the dynamo is good but regulator has failed, probably terminally so will be buying a new unit. Had I had an analogue meter in the first place I would likely have identified the problem, replaced the regulator & had the TC back on the road by now - old technology can still be best!

Thanks again
Nigel