MTFCA Forum

1925 Touring.

My ammeter shows nothing ever. Cutout throws 6.3 to 6.4v at high idle (shouldn't that be higher, like 7v?).

Battery is 6.4v at rest, drops to 5.7v - 5.9v when I turn on the lights, then back up to 6.4v when I turn off the lights.

I can't figure out whether I've got a bad cutout, bad generator, bad ammeter, some or all, or whether I'm just an idiot (auto electric is not my strong suit).

I traced the wires and everything appears to be wired correctly and the connections secure.

Next step?

Let's take the ammeter first. It should show a discharge when you turn on the lights. If it doesn't (you said it shows nothing ever), then either the ammeter is defective, or it's wired incorrectly. I think the easiest way to find out would be to disconnect one of the wires from the ammeter, and see whether the lights still work. If they do, there's a wiring problem. If they don't (they shouldn't), then the meter is defective. In other words, if the juice is passing through the ammeter and the needle doesn't move, it's defective. If your car is wired correctly, all juice in and out of the battery, except for the starter, runs through the ammeter. This does not include the Magneto - to - coils connection, which is separate.

By the way, with the wire disconnected from the ammeter, the engine shouldn't run on BATT, either. It could still run on MAG.

Now to the generator/cutout. If you measure essentially battery voltage at the cutout's output terminal at all times, then you're right - there isn't any charging going on. It could be either the generator or the cutout at fault, and further testing is required to find out which. The normal resting voltage of a battery is 6.3 volts, give or take a bit. To charge it, you need a higher voltage - just as you said.

Not 100% on this but with a quick look at the diagram I think if the meter's NG he's got no power to the gen to begin with so no chg.

This morning I disconnected the ammeter and the headlights still worked, so I guess I'll need to trace the wires again.

In the meantime, how best to troubleshoot the generator issue? Begin with a new cutout? and go from there?

Thanks for the advice

If you have been running with no battery voltage applied to the generator, due to a bad cut out or wiring issue, the generator may have self destructed. Remove the generator, connect battery and ground to it and see if it will motor. Also best to get the MTFCA electrical book. Search this forum for wiring diagrams.

Scott,

I will try to get you, step by step, to find the problem.
- Disconnect the yellow black wire at the cutout output. Connect a test light ( 12V 10W) between the Generator and the frame. Start the engine and run at a brick idle. The light should light up, not bright, take a volt meter and measure the tension over the light. It should be about 6V. Speed up the engine, the tension should rise +7V and the light should become brighter. If not the generator need a rebuild. If ok see next step.

- Connect the test light and volt meter at the cutout output and the frame. Start your engine. If Ok, you should find the same result only due to the resistance of the cut out the tension will be a little lower ( about 0.2V) If not Your cutout is shot.

- Reconnect the generator wire at the cutout output and repeat the tests with the Ampere meter disconnected by connecting the light and Volt meter at the wire coming from the generator cutout. If the wire is ok you should find the same results if not you have a wiring problem.
- If Ok reconnect the generator wiring to the Ampere meter and disconnect the wire going to the switch. Connect the testlight to the Ampere meter and test again the same way.

Go on this way at all the connections between the Ampere meter and the battery and somewhere in the loop you will find a problem.

Good luck
Andre
Belgium

If you are starting the engine with a starter and the generator doesn't charge, your battery will go dead. I think your problem is that the ammeter is not in the circuit but the generator is still working.
Norm

Norm,

I think Scott has a charging problem too because , when switching on the lights the battery drops to 5.7V .
He need to test the all circuit to find his problem.

Andre
Belgium

I'll have to amend my original post:

It turns out that at fairly high rpm (when you wind up low about to shift to high) the ammeter starts indicates charge (about 7 or 8v), but still nothing at idle.

Is this an indication that the generator is probably okay and the cutout is the problem?(please God, let it be so!)

Thanks

Does the generator have the cover still on it on the brush end? If it does take it off and do a visual check to see if the armateur is dark or not very brite. It may be dirty enough to cause the generator not to charge. And if it does it would intermittent at best. Clean up the armateur using WD-40 on a rag and clean it up the best you can by using your finger with the WD40 soaked rag. With the engine off of course! Rotate the engine to do the other side of the armateur.

Any older engines that have a generator with brushes and after lots of use do get dirty and Model T’s are no different. Old tractors do the same thing about intermittent charging. Simply cleaning them can make a difference.

John kuehn wrote: ↑

Fri Jun 21, 2019 1:55 pm

Does the generator have the cover still on it on the brush end? If it does take it off and do a visual check to see if the armateur is dark or not very brite. It may be dirty enough to cause the generator not to charge. And if it does it would intermittent at best. Clean up the armateur using WD-40 on a rag and clean it up the best you can by using your finger with the WD40 soaked rag. With the engine off of course! Rotate the engine to do the other side of the armateur.

Any older engines that have a generator with brushes and after lots of use do get dirty and Model T’s are no different. Old tractors do the same thing about intermittent charging. Simply cleaning them can make a difference.

Hot damn!! That worked!

Pic is the ammeter at low idle.

Thanks a ton!

Good to see it working! That’s what you call a simple farm fix. I learned that trick from an older T friend years ago. No rocket science here. Just common sense. Just watch the meter and see how long it lasts. Probably in the long run you might have to rebuild the generator but now you know what it is and what to first look for. Good luck.