MTFCA Forum

Sorry to keep hounding on certain subjects..... I bought this car the last week of March. I haven't driven it very far or at night. It has a 6volt Optima battery (I think). I have never charged said battery. The Ammeter never ever shows a charge. Never. It will show a discharge if, and only if I turn the lights on. I've had many other generator era cars and trucks. I'm no stranger to what that system means. With my '55 Chevy truck when I pull up to a stop sign and the truck engine returns to idle the Ammeter shows discharge. When I speed up it shows charge. However, is the 'T' different? How can this car still be able to start if the generator isn't generating? Are those batteries THAT good? I've read up on how to test them and the next time my helper is available I plan to do that. Last night I switched the wires on the back of the Ammeter because, even though they were wired correctly, they always showed a charge when I turned the lights on. Now it shows a discharge when I turn the lights on. Still no charge. Does the Model T Ammeter just never show a charge? I checked the other wires with a meter and they all appear to be wired properly. Also, probably not related.....the magneto quit. I know how to test for that, too and will maybe tonight.

The model T ammeter shows a charge when the generator is charging the battery. If yours doesn't, there's gotta be a problem. There is a way to see if the generator is working. You "full field" the generator by connecting the field terminal of the voltage regulator to the positive battery terminal. This is a correct procedure for cars with a DC generator and a grounded regulator. Perhaps someone more knowledgeable then I on the T's three-brush generator and cut out relay can explain how you full-field a T. The purpose of full-fielding is to force the generator to it's maximum output.
I would be very surprised if your ammeter is bad; if it shows a discharge, it should show a charge if there is one. There is only one electrical path through the ammeter; it either has continuity or it doesn't. If it doesn't, the meter shouldn't work at all.

If you have a generator on the car, it should be connected through the cutout to a terminal strip on the firewall. From there it goes to the same side of the ammeter that the lights are connected. The other side of the ammeter goes to the ignition switch and back to the terminal block to another terminal on the block. From there it goes through the loom to the starter switch. The same side of the switch which is connected through the cable to the positive side of the battery. I don't know anything about the Optima battery, or whether it should be charged by the generator, but the original lead acid type battery is charged through the above system by the generator. As the current goes through the ammeter from the generator to the battery, it should show charge. If the lights are turned on without the engine running, the ammeter should show discharge. If the generator is working it would show less discharge with the lights on than when the generator is not working. The generator can be set to charge enough to read zero with the engine running and the lights on. But I would recommend not to charge that much unless most of your driving is done with the lights on. From your post, I would say the light circuit is connected correctly, but the charging system might be connected to the wrong side of the ammeter. Or if the optima battery should not be charged, maybe the generator is out of the circuit.
Norm

I thought we've been thru this.
Does the generator work?
With a test light or analog meter. Meter preferred to read how much voltage. With the T not running. Check for voltage @ the wire from the cut out. You should read battery voltage. Check @ the gen output terminal. You should have NO voltage.
Now start the car, check both places again. Check, also with the motor running @ a moderate speed. You should have voltage @ both places. If you have power from the gen terminal, your generator is working.

Do this simple test & Report back.

If your starter spins fine and starts the motor, your Opitima battery is likely ok. Yes, the generator will charge an Optima, mine does fine, But, my T has the FP Voltage Regulator, not a simple Cutout, so the amp shows a charge initially, then drops off to zero, as the Optima battery is so good at holding a full charge.

Refer to the Service Manual for methods to check. No ammeter charging is sign of no generator or a bad cutout preventing current flow back thru the ammeter to the battery. You have current flow from the battery thru the ammeter when lights were on…so ammeter functions ok.

Issue is charging by the generator. My simple test for the generator is to remove the cutout off the body of the generator, then, with motor running, ground the generator output terminal to the frame or engine block with a screwdriver blade. Should see sparks! If no sparks your generator is not genning. Can’t make electricity, needs fixin.

I have a '26 T roadster with a generator and 6 volt Optima battery. The generator has a stock type cut out. The generatror charges the battery just fine, and the ammeter behaves as an ammeter normally should, which is to say that it shows some amount of charge whenever the generator is charging the battery, and some amount of discharge at idle or when the lights are on at low speeds. When the engine is off, the ammeter shows zero, unless the lights are turned on, in which case it shows discharge.

Scott at this point you must be frustrated and I would suggest you take the generator to a auto electric shop and have it tested for peace of mind. There are several repair shops within 40 minutes of Pella Iowa. Most of the time here they don’t charge you to test. It might be different where you live. I think it’s been suggested that you take the generator back to whom ever rebuilt it for testing but that may not be possible or you probably would have done that already. The result of having it tested will give you resolution to your next steps needed. Hopefully it’s something simple and will just need a second set of eyes that are dispassionate about the generator. Good luck John

JTT3 wrote: ↑

Thu Jun 23, 2022 2:40 pm

Scott at this point you must be frustrated and I would suggest you take the generator to a auto electric shop and have it tested for peace of mind. There are several repair shops within 40 minutes of Pella Iowa. Most of the time here they don’t charge you to test. It might be different where you live. I think it’s been suggested that you take the generator back to whom ever rebuilt it for testing but that may not be possible or you probably would have done that already. The result of having it tested will give you resolution to your next steps needed. Hopefully it’s something simple and will just need a second set of eyes that are dispassionate about generator. Good luck John

Yes, quite frustrated! I'm actually working on selling it, but I would like to nail a few things down on it so I know what to tell prospective buyers. Not selling it because I'm frustrated, but mostly I've spread my efforts out too much with getting this project with all my others......

Well when you meet the Popeye stage”I’s had all I can stands because I can’t stands no more” it’s probably best that you either let it sit for a while until you catch your second wind or as you suggested cut the pain point and move forward. Hopefully you’ll do the latter. Best to you.

Do what John Karvally suggested you do in his post at 1:56PM today.

Are Optima batteries that good you ask? Yes, they pretty much are. And, as you've been told, besides the momentary load of the starter, there is very little else to drain the battery, especially when your lights are off and your magneto works. You could literally go for weeks like that, assuming it's not your everyday driver.

"...I switched the wires on the back of the Ammeter because, even though they were wired correctly..."

Maybe the wires were placed correctly, but the ammeter was not internally wired correctly. It happens...

A quick check is to measure the voltage on the cutout terminal without the engine running.

The wire from the battery through the ammeter to the cutout is always connected and the reading should be the same as across the battery terminals.

About 6.4 volts if the normal wet cell battery is fully charged and a little more or less with the Optima battery.

Then measure the voltage again with the engine running at a fast idle and the reading should be about 1 to 1.5 Volts higher if the generator and cutout are both functional.

A Model T solenoid is a simple switch that opens and closes its contact points on a preset voltage. So if that's off and the points stay open the generator will work properly but nothing can get to the battery. A semiconductor (diode) type works a bit differently, more like a check valve for current (not voltage). Its function is to prevent current from flowing back to the generator from the battery when the engine is shut off. Depending on how it fails either the generator would run like a motor or nothing would pass through it in either direction.

So what type do you have, I may have missed that answer?