Not charging!

[Simon TR4a]

Since the rebuild I have had a problem with the red charging indicator glowing, ammeter reading confirms a discharge and finally, the battery eventually goes flat.
I took off the generator and had it tested at an auto electric shop, suspecting my work since I had taken it apart and cleaned it, freeing up the stuck brushes and painting the case before putting it back on the care. In spite of my efforts, the generator produced lots of output, about 35 amps.

I changed the voltage regulator as a unit, using a spare I had in stock, still no improvement.

I purchased a rebuilt generator (correctly polarised) and installed that, still not working. Any simple explanations come to mind before I take it back to the electric shop for diagnosis?
Thanks, Simon.

 

[TR3driver]

That pretty much leaves the wiring. Rather than going back to the shop, I'd suggest buying a digital multimeter (adequate units can be had for under $20) and making a few simple tests yourself.
https://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=92020

First, check that the ground (terminal E) to the control box is good. Start the engine, leave it at fast idle, and check the voltage between 'E' on the control box and the battery ground post. Should be zero. If not, the ground wire is broken or not making good contact.

Next check the voltage (engine still fast idle) from terminal D to ground. If you find battery voltage here, then the wiring to the light on the dash is bad (possibly the other side of the light got grounded instead of connected to ignition ?).

If you don't find 12-14v on 'D', then shut the engine off, disconnect the F and D leads at the control box, and temporarily join them together with the voltmeter to ground. Start the engine and watch the voltmeter; it should easily rise to 15v at just a fast idle.

If not, repeat the test except joining the two terminals right at the generator (with a jumper). If you now get 15v, the wires between the control box & generator are bad.

There's more, but that should get you started in the right direction.

PS, wouldn't hurt to repolarize the generator either. Sometimes they can lose polarization just being installed. And since a 4A is opposite to a TR4, even though they take the same generator, it's easy to make a mistake when doing it off the car.