MTFCA Forum

Looking for input on an electrical issue. Running on either BAT or MAG, my ammeter is showing 20A charge. Light switch is off and lights not yet connected. I removed the cutout cover and the points are clean. Voltage at a high idle is 8.9v at the GEN terminal. I realize that I can adjust voltage down to 7.2V with the 3rd brush, but am wondering what might cause such a large charge rate? When reversing the ammeter terminals I get a 10A discharge. Until I figure out the issue, I have removed the cutout and grounded the genny.

Someone posted the instructions for setting up a Regan VR, Use that procedure to adjust the third brush down to a much lower charge rate. 20 amps will cook the generator. My question is, do you have one of the small repro ammeters for a 26/27, or one of the large ammeters from an older model. The repro meters are not accurate at all. viewtopic.php?f=2&t=35914

I'd try another ammeter.

You need a good, fully-charged 6 volt battery with good connections for the generator to work as it should. If you test voltage with the engine running at high idle with a charged battery, it should not be over 7 to 7.5 to volts, and less is probably better. Current should max out at 4 to 6 amps.

20 amps is crazy high. The ammeter should read the same amps under the same conditions with the connections reversed, except the + and - will be reversed.

Be sure the engine is well-grounded to the frame and that all connections, including battery connections and battery ground to frame are clean and tight. Poor connections will cause crazy stuff to happen and can cause odd test readings.

Your battery is taking 8.9V. That sounds out of the limit for a good 6V battery. First I do a load/voltage test on the battery. Check running @ the battery to confirm generator output is actually reaching the battery. Could be a bad connection. Check @ clamps & posts.
By adjusting your 3rd brush, you are not turning down the voltage, you are turning down the amperage output.
Yes, reset the gen output to 4 amps.
You can put an analog ammeter (modern) between the cutout terminal & the hot wire going to it to get an accurate amp reading.

BUSHMIKE wrote: ↑

Fri Apr 14, 2023 1:07 pm

Looking for input on an electrical issue. Running on either BAT or MAG, my ammeter is showing 20A charge. Light switch is off and lights not yet connected. I removed the cutout cover and the points are clean. Voltage at a high idle is 8.9v at the GEN terminal. I realize that I can adjust voltage down to 7.2V with the 3rd brush, but am wondering what might cause such a large charge rate? When reversing the ammeter terminals I get a 10A discharge. Until I figure out the issue, I have removed the cutout and grounded the genny.

The adjustment to the 3rd brush is to set the high point of the desired amperage (no more than 10 amps is recommend). It does not regulate voltage per se.
The reading you get when reversing the terminals on the ammeter is what you should expect with the lights on (+ or - some running on BAT). Not sure what your getting with the lights off with the reversed terminals. If properly wired running on MAG only reduces a small a amount of amperage that the coils use when running on BAT, they are two separate circuits.

All the stated causes are possible. But it would be best to have the ammeter setup as you did with t he reversed connections and report back the results whren running on BAT once with the lights off and another reading with the lights on.
You also needs to state what ammeter you are having the issue with. Large or small, original or repro.
Some small repro's have had issues. Old ones can go bad as well

I think the generator brush plate lead is not property set.
If your generator is avowing a charge rater of 20 amps the generator is not going to last long.
Try resetting the brush plate lead using the following procedure.

Adjusting the Model T Generator Brush Plate Null Point with the Generator Installed on the Engine
In many cases the Model T generator brush plate lead has been fiddled with by people who do not understand what they are doing. The result is usually a generator that is charging excessively, not charging at all or will not “build up” and starting charging on its own. Here is a procedure that will allow you to correctly set the third brush plate lead with the generator mounted on the engine as opposed to removing the generator and setting the brush plate lead on the bench. .
You will need a helper to watch the ammeter and report results to you while doing this.
1. Loosen he third brush clamping nut and move the third brush to the fully retarded (counterclockwise as viewed front the front of the car) position.
2. Tighten the third brush nut just enough to hold the third brush from moving.
3. Start the engine, run at a moderate speed and loosen the four 6-32 brushplate clamp ring machine screws on the end of the generator brushplate cap about one full turn. These four screws should have lock washers to prevent them from coming loose.
4. Using your fingers (Don’t worry, you won’t get electrocuted, but you may feel a slight tingle) rotate the brushplate inside the brush cap back and forth till you find a point where the Ammeter registers 1- 2 amps charge.
5. Without moving the brushplate, tighten the four 6-32 machine screws.
6. Now set the third brush to the desired charging rate and tighten the third brush clamp nut. During the Model T era drivers operated their cars on short trips and at low speeds. To keep the Battery fully charged it was necessary to set the Generator to the Ford recommended 10-12 Amps charging rate. This situation is not the case today; Model T’s are driven at higher speeds and on longer trips.
The Model T Generator has a sustained capability to produce 100 Watts of power. This means you should keep the charging rate as low as possible and still keep the Battery fully charged. Under normal driving conditions the Generator charging rate only needs to be set for 5-7 Amps. The 5 Amp rate is optimal to keep the Battery fully charged. If you drive a lot at night with headlamps you may find the 7 Amp rate better for keeping the Battery fully charged. After starting the engine it only takes a few minutes to replace the current used by the starting motor. Setting the charging rate too high will require constantly checking and replenishing the Battery water.

Yes, it is a repop Ford logo small dia. Ammeter complete with MADE IN CHINA sticker proudly plastered on.

Read carefully
"Looking for input on an electrical issue. Running on either BAT or MAG, my ammeter is showing 20A charge. Light switch is off and lights not yet connected. I removed the cutout cover and the points are clean. Voltage at a high idle is 8.9v at the GEN terminal. I realize that I can adjust voltage down to 7.2V with the 3rd brush, but am wondering what might cause such a large charge rate? When reversing the ammeter terminals I get a 10A discharge. Until I figure out the issue, I have removed the cutout and grounded the genny.

One would expect the ammeter to register the same with the terminals reversed. Since not everything is wired so there is a possibility of a short.
I.m sure we all know never to tell the mechanic what you think is wrong and needs o be fixed, because they would fix that $$ & also fix the real problem $.
--
Suggest testing with the ammeter connected properly per wiring diagram.
-with the engine off what the ammeter readings are with the lights off vs on.
-with the engine on running on BAT what the ammeter readings are with the lights off vs on.
-with the engine on running on MAG what the ammeter readings are with the lights off vs on.

Thank you all for the suggestions. Before I tore into anything else, I thought I would wire up and try an original 26/27 instrument panel with older ammeter. I was happy to see the 9 amp charge at high idle. Both MAG and BAT read the same 9 amps. Maybe my “problem” was buying and trusting a repop sub quality ammeter. Tomorrow , I will set the charge rate on the genny as advised. I wish I had on hand all the sockets to wire up my headlights as another test.

MADE IN CHINA: WWIII.

That charge rate is within reason, and would be OK for general day to day (and night) driving. For occasional, mostly daylight driving, or longer trips, experienced people recommend a lower setting.

With the setting as-is, you can prevent battery overcharge by using the headlights to reduce the output. However, that will still have the generator working at around 10 amps most of the time, which may shorten the generator's service life. Brushes would certainly wear faster, and the average HP consumption of the generator would be higher, as would loading on the timing gears. The HP demand is small, but it is deducted from a limited supply.

BUSHMIKE wrote: ↑

Fri Apr 14, 2023 5:57 pm

Thank you all for the suggestions. Before I tore into anything else, I thought I would wire up and try an original 26/27 instrument panel with older ammeter. I was happy to see the 9 amp charge at high idle. Both MAG and BAT read the same 9 amps. Maybe my “problem” was buying and trusting a repop sub quality ammeter. Tomorrow , I will set the charge rate on the genny as advised. I wish I had on hand all the sockets to wire up my headlights as another test.

Your repop ammeter "might" need a bit of soldering to get it to work properly.
Check the video out applies to both Model T & A repro ammeters https://www.youtube.com/watch?v=n85WuQa ... eRefresh=1

T Headlights and a single tail light will draw about 4 to 6 amps with original style headlight bulbs. Higher wattage headlight bulbs will draw an additional 2-3 amps, based on my experience. The ignition system on battery would draw about 1.5 amps average, maybe a little less. The amp draw of the battery will vary based on its state of charge and general condition.

You can check the suspicious ammeter by connecting it in series with a known good ammeter. And of course, the magnitude of the reading should be the same when reversing polarity. FWIW, jb

1 1/2 year old old post.
The "information" from JW reads like AI BOT bull S##t.

The first test is to reverse the wires on the ammeter and see if you get the same readings both ways.

The best choice is to buy an ammeter adapter that is used to attach the small 1926-27 ammeter in the earlier ignition switch panel.

Then, you cut or grind out the center section and any modern two inch ammeter will fit and work.

That is especially good, if an alternator has been installed that will provide more than 20 amperes.

This is one of my examples.

You may have to put the ammeter through the switch panel first and then connects the adapter to the meter and install the three screws or install the screws first and then connect the adapter hold arms.

The earlier ammeter rings are brass, they cut out easier than steel, and still work fine!

I was told the new small ammeters were greatly improved.

I have converted a few with this one from Tractor Supply, but it is made in China too.

There have been no known problems!

Please stop! A bot brought this back after 18 months. Lets not keep beating this dead horse.

speedytinc wrote: ↑

Thu Oct 17, 2024 1:50 pm

1 1/2 year old old post.
The "information" from JW reads like AI BOT bull S##t.

Who is JW? Must have gotten removed because the first new post is this one.

Even if it did get solved, there is still good information that might help someone else.

I sure appreciate this revival, just for Ron Patterson's contribution.

Allan from down under,

Factual information, well-presented, is timeless.

I sure appreciate this revival, just for Ron Patterson's contribution.

It might have been a 'bot revival' but I also appreciated Ron's advice, especially as I am having genny issues at the moment.

RIP post, and thanks for the reminder from Ron.