MTFCA Forum

My generator wasn't charging so I cleaned the armature and got it going but was surprised when I checked the voltage. I was expecting made 9 volts but it was bouncing between 12 and 14 before the cutout and just over 6 after the cutout. Is it normal to get that much juice out of the generator?

Sounds to me like your cutout is not working i.e. not connecting the generator to the battery.
Ron Patterson

I'd follow these instructions and then test again https://modeltfordfix.com/adjusting-the ... patterson/

Joshua,

You didn't say, but if the generator is back in the car, it's a -ve earth vehicle, it's 6V, you have the throttle up a little, and you're simply measuring between earth and each side of the cutout, then most likely Ron is correct and the cutout is faulty. It's also vaguely possible that poor connections around that area could result in erroneous meter readings too, but if they're tight and clean then the likely issue returns to the cutout. In theory you could also just measure across the cutout and determine if there's a significant voltage drop.

Assuming the cutout is at fault (and that it's a mechanical cutout) then you could try cleaning the points, or replace it. If it's a solid-state cutout then you could replace the diode (and/or repair any dry joints internally), but in either case I suggest you'd be better off fitting a regulator as it will be better for your battery over time.

After you've sorted the issue you could follow Ron's instructions to adjust the generator that Frank has linked, but there's probably not a lot of point beforehand.

Luke.

Josh
Your original post indicates the cutout is not closing providing the mandatory load for any third brush generator.
The generator is doing what third brush generators does when running without a load, going beserk impressing excessive voltage on the armature and field windings (a race to see which fails first) and soon completely destroy itself therby lighting a match to a $400+ bill.
Reproduction Model T generator cutouts made today are only one step above worthless so don't go there. Get a Nu Rex diode cutout or the good quality voltage regulator now being made.
After installation of the new device take the exact same readings as you originally did and report back.
Ron Patterson

Well the good news is @ the time of your test the generator was working.
DO NOT run your motor anymore without a jumper grounding out the generator output terminal or until you get that new cutout installed.

Since I don't have a variable power supply I just used my battery charger to tinker with the cutout. The points open as they should and snap closed when the 6.75 volts the charger supplies is connected to the cutout. The cutout was a little rusty and was painted under where the screw heads should be making contact. After cleaning everything I think that it is probably doing what it is supposed to. Before I cleaned it I couldn't reliably get 6.75 volts on the output side. I really had to scratch around to make a connection. Should I try it out again or just order a new one?

colonelpowers wrote: ↑

Mon Apr 15, 2024 9:24 pm

... Should I try it out again or just order a new one?

Get a new one, but FWIW I reiterate that, in my view, a voltage regulator would be a better purchase than another cutout. I also heartily agree with what both Ron and John have just said around protecting your generator while dealing with the issue...

Luke.

Well, I studied up on servicing old cutouts and managed to get it working properly and reinstalled it. Now my generator voltage is running just over 8 volts but now at high idle I am showing a charge of 15 amps. If I remember right it is only supposed to be around 2-3 amps isn't it.

At high idle, try the range of 6 to 8 amps. .... by adjusting 3rd brush.

Ron Patterson- Question for Ron Patterson; early in this post, you suggested purchase of a Nu Rex diode cutout, however, Nu Rex web site only lists a cut out for Model A Fords, in fact, the Nu Rex description says that their diode cut out is for 1928-1939 Fords. ??? (....Model A/positive ground....Model T/negative ground. (...???)

Harold

Go to the Nu Rex website. Click on charging and go to page 2. They have cutouts for positive ground and negative ground. I just looked and it is available for $73.50, so price has gone up. Might be better off with the regulator Jeff sells.

Jeff can be contacted at www.modeltstarters.com . 6 volt negative ground voltage regulator for Model T generator

Thank you Ron, Dave and Robert,...as the kids would say,....duhh, if I had just gone to "page 2", I would have seen that the description for the one even says "for Model T and negative ground"! Thanks again guys,...harold

Update and more questions. I set the third brush so that the car was producing about 6-8 amps at a high idle and both the generator and old cutout seemed to be doing their job. The generator is putting out just over 8 volts and the cutout closes at about 6.5 volts. This evening I took the car out for about a 10 mile drive. I was probably running 35-40 most of the trip. After about 3 or 4 miles I noticed that the amp gauge was showing nothing and continued showing nothing until I pulled into a gas station for a drink. Parked, I revved it a little and again 6 amps. The return trip was with lights as it was getting dark. The gauge would alternate between 6 or 7 amps discharge or none. When I arrived home I revved it while parked and again it was alternating between nothing and maybe 4 amps. It wasn't bouncing between the readings it was like you were flipping a switch. I know that I am woefully ignorant when it comes to electricity and the answer is probably obvious. I believe that with a charged battery the amps will reduce, but not to nothing,right? Even if it were that simple, what explains the needle jerking back and forth between the two read with a second or so between the movement. Sorry to be a nuisance.

It would appear there might be bad connection in the cutout. I would suggest running the engine at a fast idle until the fault appears. Then measure the voltage at both the generator and battery terminals on the cutout. If the generator terminal has a voltage higher than the battery terminal, the cutout is faulty. Could be the contacts themselves or the riveted connections. The other thing is the insulators supporting the contact mechanism. These are old and brittle, and if crumbled away can short out the generator output. This fault reveals itself if the generator voltage drops down to nothing.

I was afraid of that being the case. I had thought that the only reason why it would act like a switch going on and off was because the switch (cutout) was still failing and cutting on and off.

colonelpowers wrote: ↑

Thu Apr 18, 2024 9:09 pm

Update and more questions. I set the third brush so that the car was producing about 6-8 amps at a high idle and both the generator and old cutout seemed to be doing their job. The generator is putting out just over 8 volts and the cutout closes at about 6.5 volts. This evening I took the car out for about a 10 mile drive. I was probably running 35-40 most of the trip. After about 3 or 4 miles I noticed that the amp gauge was showing nothing and continued showing nothing until I pulled into a gas station for a drink. Parked, I revved it a little and again 6 amps. The return trip was with lights as it was getting dark. The gauge would alternate between 6 or 7 amps discharge or none. When I arrived home I revved it while parked and again it was alternating between nothing and maybe 4 amps. It wasn't bouncing between the readings it was like you were flipping a switch. I know that I am woefully ignorant when it comes to electricity and the answer is probably obvious. I believe that with a charged battery the amps will reduce, but not to nothing,right? Even if it were that simple, what explains the needle jerking back and forth between the two read with a second or so between the movement. Sorry to be a nuisance.

Meeting expectations...

Possibility:
The ammeter registers the net load on the system. That is the flow of power to/from the battery & generator
The cut-out is a switch (solenoid) the contacts are normally "open". At ore than 6.5 volts the contact close and the generator's power is used to charge the battery and provides what other power is needed. At high idle the ammeter would show 6-7 amps per your setting.

Not knowing what kind of lights you have or what other electricals... assuming filament bulbs (headlights, taillight) would be about 6-7amps

Doing the math, when the car is running and the output of the generator is equal to the amp demand of the car, the ammeter would be at zero. With the lights off for example it would show a charge.

So when you were running with the lights on the ammeter showed 0 amps. Its likely that the generator was putting out the same amps needed to power the lights, no more or less. AND your engine rpm was above your high idle setting

When the ammeter showed a discharge of 6-7 amps it means that you were running on battery because the generators voltage dropped to 6.5 volts or less. Now this could be a result of a change in engine rpm, costing a bit could do it OR a loose connection.

colonelpowers wrote: ↑

Thu Apr 18, 2024 9:09 pm

Update and more questions. I set the third brush so that the car was producing about 6-8 amps at a high idle ... I believe that with a charged battery the amps will reduce, but not to nothing,right?

Joshua,

Well done on setting the current.

Your present system will charge at a constant current, unlike a modern charging system that will reduce the current flow as the battery voltage rises to the set CV of the regulator. If you fitted a regulator, rather than a cutout, then it would behave as you were expecting, but not as it is now.

Otherwise it does appear you still have a fault. The reason why I earlier suggested you replace the cutout (pref with regulator) was just because of this possibility, and because if the cutout or connections go open it will damage the generator in time. While the problem could still occur after replacing the cutout you [hopefully] eliminate that as a source of the issue - and it's very much cheaper/easier to replace than the generator.

Luke.

Moxie26 wrote: ↑

Wed Apr 17, 2024 10:31 am

Jeff can be contacted at www.modeltstarters.com . 6 volt negative ground voltage regulator for Model T generator

Or just message me at jeff@modeltstarters.com.

I will say that I'm also making Diode cutouts that are able to handle 60A which is 2x what the NuRex cutouts handle, and are $8 less expensive. Honestly I wouldn't waste time on cutouts any longer for a few bucks more just get a voltage regulator and keep your old cutouts as a backup.