Could anyone give me some instruction on setting the third generator brush? My generator is working, but only putting out about 1.5 to 2 volts (it was repaired not long ago)My ammeter in the car permanently shows 2 amps + unles lights are on. When i first got the car it used to read about 8amps before the generator died.
Apparently it had got too hot.
I am a little confused about the setting level as the MTFC book and Ford service manual both say set at around 8 (which would be 10 on mine) or at zero with lights on, then another person in another thread said that this was way too high...
Am a little confused and tired of flat batteries (have just replaced an old one that was sick)

Sounds like you have several problems.

First, the Ammeter should read -0- unless there is a current draw. If the wire going to the generator was accidentally allowed to touch ground (the frame of the car) the high current through the meter could either burn it out or slam the pointer so it no longer reads zero or burn open a wire somewhere in the car.

I never mess with car wiring myself without first disconnecting one of the battery terminals. (Fried several ammeters in my time).

Normal Operation:

When the VOLTAGE output of the generator slightly exceeds the battery voltage (6 Volts) the cutout relay on the generator closes and connects the generator to the battery through the Ammeter. When the output falls below 6 volts the cutout relay opens and disconnects the generator as to not drain the battery through the generator.

The faster you run the engine the higher the output AMPS of the generator until you reach the 10 Amps assuming the third brush is set correctly. This generator system is called “constant current charging”.

The voltage is held in check by the battery and if something fails in the electrical path the generator voltage will increase exponentially until the generator destroys itself.

You should have a modern volt – ohm – amp – meter.

Check the continuity of the wiring from the battery through the ammeter to the cutout terminal. (Disconnect the battery or check for 6 volts at the cutout terminal (battery side).

I have taken ammeters apart to realign the pointers, some come apart easily.

You can measure the voltage out of the generator at the post that connects the cutout and determine if it is actually generating.

There will be many other threads on this site discussing the model T generator system

Jim

The 8 amps or 0 with the lights on applied to the days of driving the T to work and home after dark, or the usual night time driving. Unless you do a lot of night time driving, this setting will overcharge the battery and it is also harder on the generator, as well as slowing down the car a bit. Nowdays a setting of 3-5 amps will maintain the charge for daytime driving and if you should occasionally drive for short time at night no problem. If you plan to drive for an hour or more at night, you should set the generator for a higher charge.
Norm

If it's only putting out 1.5-2.0 volts, adjusting the third brush won't help. Try cleaning the brushes and commutator. If the brushes weren't seated during the last "repair", the commutator could be packed with carbon and shorted out.

Lift the bushes off the comm and place the spring against the sides of the bushes to hold them. Use an Ohmmeter or powered test light and check between ground and the comm segments. If you get a reading or the light burns, the armature is cooked. (shorted)

That should say "If you get a reading below infinity" for the meter. There shouldn't be a connection between ground and the commutator segments.

Chris
It has been my experience that most generator repair shops today know very little about correctly setting up a the Model T generator. They are unique using third brush regulation.
I know it's a long shot, but if your anywhere near Lexington Kentucky your welcome to bring it by my shop and we can find out what is wrong togather and fix it. I have all the right tools.
Ron the Coilman

Ron, I very much appreciate the offer, unfortunately, Melbourne Australia is just a teeny bit too far to drop into your workshop. (As much as I'd like to)
I've spent 2 days so far on a local rally and with the new battery fitted and a carby tickle, the car is running and starting much easier. As far as the generator is concerned, no dice.
I found the brush bracket this afternoon was loose enough to push around with my finger and it was right over near the other top brush (insualted one isn't it?)
The Commutator is dirty and i have managed to clean it a little, but can't take the gen out of the car at present as I need to drive it in a couple of hours. Considering that the person who repaired it only set it at about 2-3 amps, I can't imagine what has gone wrong.
Whats the best thing to use to clean the brushes? They appear to be a bit oily.

Dear Chris, After reading the above posts, just send the generator to Ron Patterson. His turnaround time is quick and his workmanship is excellent. I had two T generators rebuilt locally,(in Salt Lake City where I live), and the longtime reliable shop screwed-up both of them. Mr. Patterson is a class act. I run a restoration shop, and you can't afford to go back and do a customer's car twice. Just send it to Mr. Patterson, thanks, Hugh

It's easy to spend other peoples money but I would clean the comm and do the test. Spending $60 to ship it to the US just to be told you need a $90 armature is ludicrous to say the least.

Chris
As Ken suggested clean the commutator to bright copper by placing a norrow strip of sandpaper on your finger and push it agianst the commutator when the engine is running.
Check the internal generator wiring. The two field wires should be crossed and one end goes to the smaller third brush and the other to the grounded (earthed for you) large brush holder. The generator output terminal is connected to the large insulated brush holder.
Now do this. With the third brush set all the way retarded (counterclockwise when viewed from the gear end)and the nut tightened and loosen the four brushplate assembly screws on the end cap. Start the engine and run it at a moderate speed. With a helper to watch the dash ammeter move the entire brushplate assembly in the cap back and forth until you find the spot where the ammeter is reading 1-2 amps. Tighten the four brushplate clamp screws. Now loosen the third brush nut and advance the third brush until the ammeter reads 5 amps.
If this doesn't work there is a fault in the generator.
Ron the Coilman