View Full Version : TR2/3/3A TR3 not charging?

09-04-2006, 08:02 PM
My ampmeter shows a slight discharge with no appliances on and when the headlights are pulled on it pegs to the left. Sunday I was about to take it to our all British car show and the battery was pretty close to dead. Now I'm trying to figure out from my old Hanes manual how to check the generator to see if its charging. It says Pull the D and F leads of the "dynamo" (generator)and join the terminals (D and F) together with a short length of wire. Then it says attach to the centre of the length of wire the negative clip of a 0-20 volt voltmeter and run the other clip to the earth on the dynamo yoke. I'm not sure I understand -- the center of which wire: the bridge between the D and F? Do I really bridge D and F with a length of wire?

Geo Hahn
09-04-2006, 08:27 PM
From "The Best of Geo" this tidbit:

Some basic charging system tests (note that if your car is positive
ground, all the voltages are negative) :

Engine off :
1) Double check the mechanical stuff : fan belt present and snug,
generator snug on mounts, wires firmly connected to generator, etc. You
should only be able to turn the generator fan with great difficulty, if
at all. If the generator has been off the car, it's worth repolarizing

2) remove the wire from the 'F' terminal on the control box
(regulator). Measure the resistance between the F and D terminals, it
should be under 1 ohm. If not, the control box is bad.

3) Measure the resistance between the wire that came off the F terminal
and ground. It should be between 5 and 10 ohms. If not, either the
generator or (more likely) the wiring is bad.

Put the wires back, Start the engine, and set it for a fast idle
(1500-2000 rpm)

4) Terminal E to battery ground post should be under 1.0 volts. If not,
you have a bad ground. Also check from E to the generator housing.

5) Measure D to E. This should be around 13-15v, if it is then the
generator is working. Higher indicates a bad regulator.

6) Assuming D-E is under 13v, compare it with A-E. If they are the
same, the ignition lamp should be out. If not, the wiring to the lamp
is wrong.

7) Also assuming D-E is under 13v, check D-F. It should be under 1.0v,
if not, the regulator is bad or badly misadjusted. One exception to
this is if the ammeter is reading a lot of charge at this point, 15 amps
or more, which could indicate a bad or deeply discharged battery.

8) As a final check, (again assuming step 5 was under 13v) stop the
engine, remove both wires from the generator, jumper the terminals
together and connect the voltmeter from either terminal to ground.
Start the engine. Rev no higher than about 750 rpm, and check the
voltmeter reading. If you don't get at least 15v, the generator is
definitely bad. According to the book, around 4-8v indicates a bad
armature or brushes, around 1v indicates a bad field. If you do get
15v, reconnect the wires and repeat the test with the F and D wires at
the regulator. If you get different results here, then the wires are

09-04-2006, 09:35 PM
Had already checked all of number 1 but too dark/late tonight for the rest-- will start those tomorrow. This looks clearer than the Hanes! Thanks again, Geo.

09-05-2006, 09:06 PM
Well, I started through the checklist-- got past #2 and measured #3, resistance between the detached F terminal wire and ground. Almost zip. To test whether the wiring was bad between the generator and Voltage regulator, I went directly to the generator, F term and got resistance between it and the ground. Cleaned up both spade connections, re-attached and tightened them real well and bingo-- resistance checked adn after starting the car,ammeter showed slight discharge at normal idle and charge when revved! Took the car out and went "charging" about the neighborhood, quite happy not to have to do more detective work and parts replacement (at least not yet). Yet again, Thanks Geo.