Triumph Repair: Triumph Charging System, pig tail, moss motors

Question
Been wrestling with the charging system on my 1966 TR4A for awhile now.  Seems everything is in spec finally and the ammeter behaves as it should; the problem is the generator warning lamp.  At idle it is out, but as I increase RPM, it starts a faint glow which increases with RPM but not to the point where I would say the bulb is full on.  It is a VERY faint glow without load, but a noticeable glow under load (headlights).  Found a paper which made a very compelling case for reversing the A and A1 leads on the regulator to even out the charging. Tried it and it did level out the peaks and valleys (charge/discharge).  Switching the leads back to stock had no impact on the glow.  Generator was rebuilt (brushes and bearings) about 3 years ago.  Regulator was new two years ago with a unit from Moss Motors.   Appreciate any insight you might have.

Answer
Hi Dan,

The tests we used at the dealership were simple. We first tested the battery voltage (12v +) then we left the volt meter attached to the battery posts (not the cable ends) and started the engine and put the RPM up to about 1500 RPM and read voltage. It should read 13.8v to 14.5v but not more.

If it did not read that we used a jumper that we each had made of a long piece of 12 ga wire to reach from the back of the generator to the battery. On one end we attached a short piece of 14 ga wire. On my test lead I had a large female spade connector on the heavy 12 ga wire and a small female flat spade connector on the pig tail coming off of the main 12 ga lead.

Disconnect both wires from the back of the generator and attach your 12 ga test lead to the large "D" terminal on the generator and the 14 ga pig tail to the smaller "F" terminal on the generator. Now both the "D" and the "F" terminals are connected together on your test lead.

Now, have someone start the engine and set the RPM at about 1500 RPM and just touch the hot post (hot post on your car should be the (-) negative post) on the battery (not the cable end) and read the volt meter across the battery. Don't leave the test lead connected long, just enough tome to read the volt meter. It should read about 15v.

This is called "Full fielding a generator"

If all that is correct check the wiring and as for "A" and "A-1" the battery (heavy brown lead) should be connected to "A" and the ignition switch should be attached to "A-1" and you should not switch those leads.

The "F" lead gets the small field wire from the generator while the "D" terminal gets both the "D" (Dynamo) lead from the large "D" wire from the generator and the small Idiot light wire from the instrument panel. "E" gets the black ground (Earth) wire.

If all of this it correct you need to run "voltage drop tests" on each wire while under load (Operation). Especially the ground strap from the engine to frame and frame to body and to the battery.

A dim charge light (Ign light) can be caused by a number of things. Poor wire or battery cable connections, poor ground straps, dirty contacts in the regulator, poor brush to commutator contact, Even a wrong WATTage bulb in the charge light. (2.2W)

Howard