Board index Flathead Power-Technical Questions, Answers, and Suggestions 45 Flatties Charging Problem

Charging Problem

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Post Mon Apr 21, 2014 1:04 pm

Posts: 30
Location: Winnipeg,Canada
At the end of last riding season, my battery was discharging every time I ran the bike. The battery is two years old, and is a Genuine Harley part. It will take a full charge from a charger, but dies quickly when run in the bike.
Over the winter, I rebuilt the generator, new coils, armature, and brushes. I also purchased a new relay.
Today,I installed the generator (flashed it between the generator relay terminal and the battery positive), relay, and battery and fired her up. With an ammeter installed between the battery negative and ground, I am only getting a reading of about one amp. I've tried adjusting the third brush on the generator through it's full range of travel, but the most I can get is one amp. Where should I be looking? Is it pssible my battery is defective or is it more likely a bad wire somewhere in the charging system?

Post Mon Apr 21, 2014 5:36 pm

Posts: 783
Location: Victoria, Australia
With an ammeter installed between the battery negative and ground

The amp gauge should be between the battery + and the positive output of the generator. Looking at the wiring diagram (WLA) it should be fitted between the red wire exiting the cut out relay. It should then indicate all charge and discharge to and from any component or device drawing current.

Page 183 this link:

You may have a faulty armature and or field coils, did you checked these components with a meter when you were rebuilding the generator? I wired mine years ago to function as a 2 brush, 6 volt generator (and fitted a suitable relay) I use a small 6 volt sealed battery (2" x 3" X 1.5") and dumped the original giant brick. The system works fine and it easily runs the headlight and 2 small spot lights in unison without discharge.
I did this conversion based on the expert advice of Dr Dick (Frankenstein) years ago and it's functioned perfectly ever since.

Post Thu Apr 24, 2014 6:53 am

Posts: 30
Location: Winnipeg,Canada
I took the battery in for testing and it failed a load test, only 2 volts under load. There is a short in one of the cells. I've ordered a new battery . Once the new battery is installed I'll recheck the rebuilt generator's output.

Post Mon Apr 28, 2014 10:17 am

Posts: 30
Location: Winnipeg,Canada
I installed a new battery this morning and now I want to check how many amps my rebuilt generator is outputting. The service manual says it should be set at 4 amps. I'm thinking to test the output direct, I should bypass the electronic relay , so I've used a jumper between the battery positive terminal and the generator relay terminal (after disconnecting the relay terminal wire). I have the ammeter connected between the battery negative terminal and ground. I'm getting the following readings:
-With no lights 7 amps at idle 4 amps engine running faster
-With lights 8 amps at idle 4 amps engine running faster
Am I doing this correctly, or is there a better way to check the generator output?
Should I be adjusting the output lower?

Post Mon Apr 28, 2014 5:39 pm

Posts: 783
Location: Victoria, Australia
Did you refer to the army manual for the WLA above in this thread. It should outline all the info you need to check the charging system and the procedure to adjust it.

Post Mon Apr 28, 2014 6:47 pm

Posts: 30
Location: Winnipeg,Canada
I know you can adjust the generator output by moving the position of the 3rd brush, but the manual doesn't show how to test the output. I have a civilian 45 manual and it doesn't show neither how to test the generator output.

Post Mon Apr 28, 2014 9:32 pm

Posts: 783
Location: Victoria, Australia
Use your multi-meter (set to Volts DC) to first test your battery for 6 volts. Perhaps at rest (engine not running it will read about 6.2 volts.) Start the engine and check that when it is running it is putting out 6.8 to 7.2 volts or so. If the bike shows a discharge adjust the 3rd brush till it shows a positive charge. Switch on the headlight and any other electrical ancillaries and check the charge rate again. Adjust the 3rd brush to accommodate this. With all the electrical ancillaries on, the voltage output at the battery should be greater than 6 volts. All you require is more going in than is being drawn out.

I have the ammeter connected between the battery negative terminal and ground.
? How can this work?

Operation and Maintenance Manual. Page 51. Generator Charging Rate.
A maximum charging rate of about 4 amps (with regular equipment lamps lighted) is the standard factory setting.

Post Tue Apr 29, 2014 8:34 am

Posts: 30
Location: Winnipeg,Canada
Thank-you Enigmas for all the helpful replys. On page 48 of the same manual, it says to check for problems in your charging system by jumpering the battery + to the generator and attaching the ammeter between the battery - and ground. This does give good ammeter readings. I'd still like to check the generator's amp output. Two questions:
1. Do I check the output with the relay bypassed?
2. Why do I get higher amp readings when the bike is idling and lower readings when I run the engine harder? (see above posting)

Post Wed Apr 30, 2014 2:06 am

Posts: 783
Location: Victoria, Australia
Test & Regulate Generator

Method. (Using a degree of extrapolation)

Mount the generator in a test stand (a large jawed vise will suffice) or utilize the generator as fitted in the bike if nothing else is available.
If removed from the'll need to spin it up at the gear end in an anti-clockwise direction.
Get access to a suitable ammeter and 6 volt battery.
Disconnect all connections from the generator terminals.
Connect the +ve lead from the ammeter to the relay terminal of the gen.
Connect the other lead of the ammeter to the +ve battery post.
* If generator removed from the vehicle, run a ground wire from the -ve battery post to the generator body.

This connects the gen to the regulating field coil (the same as operating with the lights off)
Run the generator either with an electric drill or start the motorbike to spin it up.
This will also warm the generator.

Try an gauge 2500 rpm and take a reading. This should be 4 amps.

Connect a jumper wire between the switch terminal on the gen and the test stand (vise) or frame.
This supplies a ground and cuts the shunt field coil into the circuit and increases the current output.

At 2500 rpm the output should be 7 - 7.5 amps.

To increase or decrease the the current output move the regulating brush (3rd brush) in or out.

Post Thu May 01, 2014 5:33 am

Posts: 1642
Location: Interlaken, NY USA

Hey Mr P-D, First, from your one response where you were placing your ammeter between the generator output and the system, your readings between 7&8 amps idling, 4 amps running indicate your genny is working. The low speed output is fine. However, your high speed output is low, probably causing your difficulties. The third brush regulates the genny output by warping the magnetic field inside the generator, and thus giving a way to roughly control its output. Amazing, Warp drive in a WWII era motorcycle :)
Don't worry how that all happens, just be glad it does. At any rate, My first guess is that you have your third brush rotated almost fully clockwise when viewed from the left side of the bike. You should try rotating it fully anticlockwise, then moving it back just a small fraction. This should be a good place to start.
What you would like to see is a small forward (charging) current into the battery under most operating conditions. Typically, people measure this by breaking the circuit at the positive terminal and inserting the ammeter. However, you may also do this at the negative (ground) terminal as well. When measured here, you look for current flowing into the ground as a proper charging scenario.
Just as a point of reference, a 32E will output about 10amps max when measured at the generator, not at the battery. At the battery, you're only seeing what amperage is left after feeding all the electrical systems, ign, lights, stereo, etc.

Now about the Third brush. The third brush control performs in a semi logical manner. (Semi logical to Humans, the electrons are perfectly happy).
At its fully anticlockwise position, the generator will have the broadest power output range, ie a relatively flat output curve over a broad range of RPM's. As you rotate the brush clockwise, you begin to peak the output and narrow the output range. The peak will occur at lower and lower rpms as the brush is continued to be rotated clockwise. Like a hot cam in an engine in reverse! Ideally, you want to minimize the clockwise rotation to what will just give you the output you need.
Hope this helps, Go Forth and Warp.

Post Fri May 02, 2014 5:38 am

Posts: 1642
Location: Interlaken, NY USA

P-D, gave you some poor info in the last post. I misunderstood position of the ammeter. When located at the neg terminal of the battery to ground, your readings look pretty good. It indicates you have a positive charge into the battery of 4 amps at speed with lights on or off. As Enigmas quoted, that's what's called for.
Sorry to mislead you. I presumed your ammeter was on the bypass lead you connected direct to the battery. Mea Culpa.

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