Generator issue?

[crumbaa]

Just fired up our 30 cab for the first time after 5 year restore project. We think the generator is not charging the battery.

The setup

1. 12 volt neg ground
2. 3 brush generator

3. new pop out
4. Polarized generator buy touching the front post of the pop out to the back post for about 2 seconds. It did spark when we did this and I could hear a bit of a hummm

5. Idle speed set normal or slightly high



Things we have done and what we observe
- with the engine NOT running and the key ON we see ammeter at zero


- with the engine NOT running and the key ON we turn on head lights and the ammeter drops to -15


- with the engine NOT running and the key ON the turn signals we installed work great


- with the engine RUNNING the ammeter reads -4 or -5


- with the engine RUNNING I move the 3rd brush from one stop to the other stop and it has no impact on the ammeter reading. Turn on the head lights and the ammeter goes to -15.



- with the engine RUNNING and the 3rd brush set all the way either direction we rev the RPM up the ammeter come up to about -3.



- with the engine RUNNING the turn signals do not flash they will make a very slight flicker but will not flash. (note turn signal are fine when engine is NOT running)



We think the generator is bad but need some feedback from those with more experience. Any help would be appreciated.

[jrelliott]

Have you cleaned the commutator with crocus cloth? Have you checked the brushes and the tension on the brushes? Have you checked the generator to see if it will motor( need the fan belt off and jumper around the cutoff). Have you jumped around the cutoff with the engine running?
These test may give you some more clues as to what is the problem. If the generator will motor( will run but at a low speed) then the generator is good.
This is the setup I am running.

[crumbaa]

Thanks for the response JR. It has helped.

There were some very sallow groves in the commutator when we took it apart so we used what I know as Emery cloth (fine abrasive cloth like crocus cloth I think) to clean it up. The brushes are all new and there is pretty good tension on all three of them.


-we took the generator off the car and took the pop out off. Connected the generator mounting bracket to ground on a spare battery and then attached the stud at the front of the generator to the hot side of the battery. It turned at what I would guess was about 100 or 200 rpm (just a guess) not fast but not like it was hesitating.


-We have not jumped around the cut out while it is running I was afraid the voltage would get into a feed loop and run away with its self. We will give that try.



-Should this jumper only be done for a short period of time? as in a few seconds to see what the ammeter reads or is longer ok while we think about what we are seeing?


/Tony

[gustafson]

where on earth did you get a 12V neg ground 3-brush genny?
There are some here that say you can push a standard issue Model A genny to 12V and change the polarity but in fact it will not work properly and leave you by the side of the road. The field coils will not hold up

[Badpuppy]

Originally Posted by gustafson

where on earth did you get a 12V neg ground 3-brush genny?
There are some here that say you can push a standard issue Model A genny to 12V and change the polarity but in fact it will not work properly and leave you by the side of the road. The field coils will not hold up

Generators produce power, not voltage. The 6v generator will produce 12v with the lower current draw. The field coils will be fine.

Try polarizing again, but your flaky results point to something going on with the generator.

You can jumper the cutout for as long as the engine is running. In fact it may have high resistance, which could be the problem.

[gustafson]

Sponsored Links (Register now to hide all advertisements)

I have seen these so-called 12V upgrades smoke the fields.
your mileage may vary.
and yes they produce voltage.
power is volts times amps

[1930.68B]

Btt

[crumbaa]

Thanks for the suggestions. We will try to polarize again with the car off. Then with it running try to short around the pop out to see what reaction we get from the ammeter. The generator was original to the car (original from the 50s when Grandpa got it) Maybe some insulation in the field or armature has degraded and it just not up to snuff. BTW thought badpuppy thought you would be interested to know the car was originally from your neck of the woods in Ada OK. Will return with results.

[Mike V. Florida]

Take a meter and from a head stud to the output of the generator with the engine off should be 0 volts. With the engine running the output of the generator should be greater then zero, and if the cutout is working should be a little greater then the battery voltage. If the cutout is not working then it should be way above the battery voltage.


If you don't have a meter, start the car, jumper the cutout and the ammeter should go from minus to plus if the generator is working and the cutout is bad.

[DHZIEMAN]

Originally Posted by gustafson

where on earth did you get a 12V neg ground 3-brush genny?
There are some here that say you can push a standard issue Model A genny to 12V and change the polarity but in fact it will not work properly and leave you by the side of the road. The field coils will not hold up

Delco-Remy had some 12 volt 3 brush gens. Not sure of the era they were around. And a model a gen will put out 12v but the wattage remains the same, hence the current output is half, since the voltage is doubled.

[gustafson]

if the OP thinks he can believe everything he reads then he can add his name to the list of people who have smoked their gennies. The tired ancient cracked enamel insulation on the field windings don't take the extra voltage and heat well

[crumbaa]

Update: We polarized the generator again, no change. Made sure the brushes were making god solid contact then then put a jumper around the cut out with it running and that had no effect. We decided to go to an alternator and that fixed the charging issue. Thanks to all for the suggestions and ideas.

[gustafson]

---

[Mike V. Florida]

Originally Posted by crumbaa

Update: We polarized the generator again, no change. Made sure the brushes were making god solid contact then then put a jumper around the cut out with it running and that had no effect. We decided to go to an alternator and that fixed the charging issue. Thanks to all for the suggestions and ideas.

I'll give you 10 bucks plus shipping for the generator.

[Purdy Swoft]

Originally Posted by gustafson

where on earth did you get a 12V neg ground 3-brush genny?
There are some here that say you can push a standard issue Model A genny to 12V and change the polarity but in fact it will not work properly and leave you by the side of the road. The field coils will not hold up

This is just another example of your ignorance , concerning the generator ... People that knew what they were doing knew that the generator would charge 12 volts just as easy or easier than it would charge 6 volts , at least as far back as the mid fifties or earlier . The generator charges the battery with amps . The ammeter registers in amps . Voltage is determined by the volts of the battery that it is hooked up to. A completely unmodified model A generator will charge a battery with a voltage of 40 volts or more. More heat is generated by amps than volts as a general rule .Most if not all model A generators that are set up to charge a 12 volt system will have the third brush set for not more than 10 amps. When the Fun Projects voltage regulator is used , the generator will only charge at 10 amps when needed , like when the lights are used . otherwise the voltage would allow the generator to cycle between 10 amps and probably around 3 amps . In other words , similar to the way that a modern system cycles between low and higher voltage on demand . The field coils will run cooler and last longer at lower amps . For the most part, with a 12 volt system when a voltage regulator is used the amperage draw from the generator will only be about half of what the draw would be with a six volt system using a cut out . The model A generator using a voltage regulator and set up for 12 volt use will be under less strain , will run cooler and last longer . The model T guys have known this for ages . John Regan , that produces the Fun projects voltage regulator is an electrical engineer . There are lots of good model A guys on this forum that uses the Fun Projects regulator . I have used them for over 20 years . If the model A generator didn't work dependably on 12 volts , these regulators would have been off the market for many years .

[gustafson]

Yikes! Thank you for your compliment

[Purdy Swoft]

Originally Posted by gustafson

Yikes! Thank you for your compliment

The way that I see it , you were asking for it !!! I could care less about what you think or do with your generator . Bad info doesn't help anyone . There are lots of model A & T owners that run the original generator on 12 volts with good results . Voltage regulators have been on the market for this type of upgrade for years . Just because it is over your head doesn't mean that it is a bad thing . I take your posts on this thread as a personal insult .

[wmws]

Purdy. I have been reading your comments for a number of years now and they have been well thought out and enlightening. However lately I have seen several of your comments that have in my opinion been rather short tempered and rude. I know you are a Model A expert but I think if you disagree with someone you could in a nice logical manner point out what you disagree with and keep the name calling to a minimum. Just remember we are all in this hobby to have fun.

[crumbaa]

Update. While the alternator we put in addressed the charging issue we still had a problem in which the turn signals we installed would not flash if the car was running. They would just barly flicker. Worked fine wile the car was not running. We were using leds with the electronic flasher. We tried adding a pair of 21 watt bulbs in parallel and no change. Put a bimetal flasher in and bingo works perfect with a buss 550 flasher. It seem the ignition was feeding into the timer circuit in the electronic flasher. Hope this helps someone else

[eagle]

The A electrical system is Very noisy, nearly as much AC as DC it seems like. You can add a simple DC filter before the electronic flasher and then it will work fine.