Generator Testing

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Model T Ford Forum: Forum 2015: Generator Testing
Top of pagePrevious messageNext messageBottom of page Link to this message  By henry h on Saturday, June 13, 2015 - 04:10 pm:

I have a generator which shows no current on the dash gauge, and no voltage on the mounting stud for the cutout when the engine is running. Now that the generator is out, are there any bench tests that can be run to get some ideas? Continuity? Grounding,? etc. I've been through some of the other posts, and don't want to start disassembling or fooling with brushes until i know there is no other option.

Thanks


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ken Kopsky, Lytle TX on Saturday, June 13, 2015 - 10:17 pm:

I would check the third brush insulator. Many times it's broken and allows the brush holder to short against the brush plate. That will kill the output right off.

Then clean it up--Commutator, brushes, etc. Make sure the brushes move freely in the holders. There's not much to check with it assembled. It works or it doesn't. When it doesn't, you need to check each part.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kevin Whelihan Danbury, WI on Sunday, June 14, 2015 - 10:06 pm:

First thing to do is take the generator if it can already be turned by hand and put it on a bench. Take a 6 volt battery charger or 6 volt battery. Place the positive (+)clamp on the positive terminal of the generator and touch the negative lead to the generator housing. Then see if the generator runs as a motor.

Second step: order the MTFCA Electrical manual to assist you in rebuilding/repairing the unit.

If all that fails, send the unit out to a reputable rebuilder.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dave Dufault on Monday, June 15, 2015 - 08:53 am:

And NOT a rebuilder of "modern" generators. Many of them do not understand the nuances of the Model T generator. Been there, done that !!


Top of pagePrevious messageNext messageBottom of page Link to this message  By John F. Regan on Monday, June 15, 2015 - 10:20 am:

I have to second the statement by Dave D. - Modern generator shops are a PITA and only charge money for no help but have screwed up a lot of generators that I am personally aware of. Majority of them will not be honest and tell you they don't have any experience with adjustable 3rd brush type generators. Also want to warn that NEVER send your voltage regulator along with your generator to any generator rebuilder. They don't need it for anything and more than 90% of blown VR's that we receive become that way at modern generator rebuilding shops. Correct setting up of a 3rd brush generator has to be done on the car - not in a shop.


Top of pagePrevious messageNext messageBottom of page Link to this message  By henry h on Monday, June 15, 2015 - 12:36 pm:

Thanks All. Are there any schematics for the generator itself?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Roger Karlsson, southern Sweden on Monday, June 15, 2015 - 01:49 pm:

You'll learn what you'll need for testing and repairing the generator in the club's electrical manual for $12 (well worth it)
The club DVD doesn't add much, but it's more fun to see Dave Huson test a generator than the regular program on TV ;)


Top of pagePrevious messageNext messageBottom of page Link to this message  By henry h on Tuesday, June 16, 2015 - 01:30 pm:

Since the 3rd brush bleeds enough voltage to create the field, what kick-starts the process. ? Where does the voltage come from to energize the field coils when the generator starts up.?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jerry VanOoteghem - SE Michigan on Tuesday, June 16, 2015 - 03:13 pm:

Henry,

The "start-up" begins with the residual magnetism in the field pole pieces. (If I'm not mistaken)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Roger Karlsson, southern Sweden on Tuesday, June 16, 2015 - 04:43 pm:

You create the residual magnetism by connecting a battery to the generator and run it briefly like an electric motor when it's been repaired just before you mount it back on the engine.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Michael Deichmann, Blistrup, Denmark on Saturday, June 27, 2015 - 06:30 pm:

But what Roger just said is NOT done with the FunProjects Voltage regulator on the generator!!! (if you have one)


Top of pagePrevious messageNext messageBottom of page Link to this message  By henry h on Saturday, July 18, 2015 - 10:44 am:

I tried flashing the gen (with the cutout removed). No luck. It's now out and disassembled. Nothing obvious. The resistance across the field coils is about 3.5 ohms. The brushes look and function mechanically ok. The insulator on the gen post was dried out with chunks missing. I don't plan to remove the brushes or mess with the 3rd brush adjustment, nor remove the field coils. Any simple suggestions regarding the armature, or other things?

Thanks


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mark Gregush Portland Oregon on Saturday, July 18, 2015 - 11:02 am:

Check for grounded brushes. Of the three brushes, one is grounded to the case the other two (movable and one other) are not. If they are then you need to replace the insulators. Get the armature tested on a growler for shorts.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ken Todd, ............Red Deer, Alberta on Saturday, July 18, 2015 - 11:25 am:

You could try cleaning the commutator and brushes with electric motor cleaner. They may have an oil film on them preventing contact.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Val Soupios on Saturday, July 18, 2015 - 01:39 pm:

On my '27 I never use the starter and keep the battery up with a trickle charger. When I crank start the car the generator shows no charge and if I flash it the needle jumps up to 8-10 amps but shortly after that it drops back to 0 again. Is there a problem or is the cut out reacting to the fact that the battery is fully charged. I am running an original Ford cut out.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Georgetown TX on Saturday, July 18, 2015 - 01:50 pm:

Val,

Sounds like your cutout is no good. 8 - 10 amps is too high for a fully charged battery.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Stephen D Heatherly on Saturday, July 18, 2015 - 02:37 pm:

Henry, I think it would be a very good idea to rebuild the brush ring. The original insulators are a paper like material and probably wrinkled up and cracked or crushed on the back where you can't see it. New fiberglass insulators are available and it is not difficult to rebuild the ring. Langs also sells brush rings which have already been rebuilt.
https://www.modeltford.com/item/5132R.aspx

Val, it sounds like there is something wrong with the generator. It should start up on it's one without being flashed. Also, it is completely normal for the ammeter to read 8-10 amps with a cutout even though the battery is charged because cutouts don't regulate the charge output.

Stephen


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