Charging system analysis

Electrical issues
Forum rules
Please do not start new topics here, but here: New Panhead and Flathead topics
Post Reply
jack moghrabi
Posts: 32
Joined: Mon Jul 14, 2008 2:59 pm

Charging system analysis


Post by jack moghrabi » Sun Jan 14, 2007 7:06 pm

Hello gents (and any girls out there)....

My usually very reliable daily driven 63' FL has been down for two weeks now with a charging system problem. I've got the 65A-12volt two-brush generator with an end-mounted Electric Frank solid state regulator that's a good four years old (the voltage regulator that is).
The battery is good and I believe all of the wiring is okay (my bike is wired real simple with a minimum of wires--I don't think I have more than a total of six wires on the bike).
I've tested the generator and she is putting out 17.85 amps. The actual amperage reading is -17.85 amps but to the best of my knowledge I don't believe the negative read-out makes a difference and just means the field circuit terminals are reversed (If I'm wrong here please give me a holler and let me know).
I've also had the generator apart several times in these two weeks (How many times I'd really just as soon not say....) and just to give the old mule an extra kick I tested the field circuit and the armature plates for continuity and they all show good. I did find the small square piece of insulation on the armature terminal screw broken so I fixed that with a new piece I cut out (however, I don't think the terminal bolt was actually shorting out due to the worn out insulation...not yet anyway) .

I tested the generator amperage by disconnecting the generator wires from the regulator, grounding out the generator field circuit to a good ground on the engine, hooking up the positive lead of the ammeter to the generator "A" armature terminal and then, with the engine running, briefly touching the negative terminal of my meter to the regulator BAT terminal to get the -17.85 amps reading.

When I got here I assumed my voltage regulator was bad and as luck would have it I picked up an Accel mechanical regulator yesterday morning from the Japanese motorcycle shop around the corner from where I live. I was driving by and on a whim I stopped by and hollered at the old timer there if he happened to have a regulator up on his wall for my old panhead. To my ultimate surprise he walked over to the wall and took down the HD regulator. By the looks of the package I think its been up there for quite a few years. The clear plastic is yellow and we couldn't even make out the price tag.

This regulator is actually for the 1965-1969 Fl (and other models of various styles and years) with the #64 12 volt generator. My generator is the 65A 12 volt but I thought it was still ok. I figured it was a good sign that the metric shop had a regulator up on the wall just waiting for me after who knows how many dickering with the old timer about the worn out packaging....he let me have it for $30. When I got home after some close scrutiny I was able to make out the price tag at $59.95. So, now feeling extra good about things I hooked up the new regulator (I grounded the regulator as per the instructions) and I'm still not showing any charging. So now I have two regulators, a presumably good generator, a good battery, and still no charging.

Is there an easy simple way to test the voltage regulator for folks like me? My manual does have instructions for conducting a voltage regulator test but it requires a seperate voltmeter, ammeter, and a field control rheostat. All I have is a digital multimeter. Before going any further however I figured I'd better put the breaks on and go back to the Source here on this site and see what any one thinks. All my thinking has still got me sitting here, $30 down with two voltage regulators and a good running machine that doesn't charge.

Any help would be appreciated. JackMO!

Posts: 964
Joined: Tue Mar 16, 2004 5:52 am
Location: Sultan, WASH

Re: Charging system analysis


Post by mbskeam » Mon Jan 15, 2007 2:00 am

if your wiring is stock, check the leed under the coil, the wire from the regulator the wire broke due to a bad crimp and corrosion.
this wire goes from here to the batt.
do you get 12+ volts at the gen?, work your way back if you do....

you will find it


my old franks did take a crap out of the blue, so I know this can happen

jack moghrabi
Posts: 32
Joined: Mon Jul 14, 2008 2:59 pm

Re: Charging system analysis


Post by jack moghrabi » Tue Jan 16, 2007 4:26 pm


Thanks for getting back to me. All I tested at the generator was for amperage like I mentioned earlier. That's what my manual says so that's what I did. I would appreciate any info on the proper way to test for voltage at the generator. Where do the voltmeter leads go?
And to do the voltage test do I need to disconnect the voltage regulator from the generator?

Also, my final test yesterday was to take the cover off the voltage regulator (the Accel mechanical regulator) and I manually closed the contact points and did the voltage test with the voltmeter terminals on the battery posts. When I did this the voltage dropped one volt, from 12.6v to 11.6v. Is this indicative of a faulty regulator? If not, any idea what it means?

A Harley mechanic from 60 miles away was nice enough to give me that piece of advice yesterday and see what happens. I just got off the phone with him and he just told me the following:

1. My test for amperage at the generator does not really mean anything. He said a bad generator can still show good amperage. He said I need to test for voltage (like you said in your reply).
2. Testing for voltage is simple enough. Ground out the field terminal on the engine and hook up the positive lead off the voltmeter to the armature terminal and ground out the negative lead of the voltmeter anywhere suitable.

3. He also said that the fact my voltage dropped when I manually closed the contact points on the regulator leads him to think my generator is faulty.

Frankly, I am still a bit confused because my manual does say to test for amperage but hey ho its all good. Any further interpretations on any and all of the above is welcome....JackMO!

Posts: 369
Joined: Sat Jun 19, 2004 2:58 am

Re: Charging system analysis


Post by kell » Tue Jan 16, 2007 8:55 pm

How about thinking of what the generator puts out as POWER, not amperage or voltage. You could test the generator's power output by connecting a heavy load, like a bank of three or so headlights, and see if it will light them up.
Disconnect the regulator, ground the generator's field, and connect some headlights to the generator's armature and an engine ground. Start the bike (on just the battery), rev it and see what happens on the load you hooked up to the generator. If it can light up three or four headlights (wired in parallel) brightly then it can run your bike.

jack moghrabi
Posts: 32
Joined: Mon Jul 14, 2008 2:59 pm

Re: Charging system analysis


Post by jack moghrabi » Wed Jan 17, 2007 7:05 pm


Thanks for the input. Checking for Power the way you described makes a lot of sense. Meantime I have found out where I went wrong:

When I initially took the generator apart and I checked the armature it seemed okay because I had continuity from copper plate to copper plate (where the brushes contact the armature), and no continuity from the copper plates to the steel shaft of the armature so no short there.... Well, I thought that was enough to rule the armature as not faulty. It's not enough. I located a shop that has a "growler" to properly test the armature. For $20 that's what they did. Once on the Growler (which I guess shoots a current through the armature), the procedure is to take a fine hacksaw blade and gently run it between each copper plate across the surface of the mica that seperates the plates. A good armature will show a lot of electrical activity between each plate when you do this, ie a lot of sparks should be flying. This is all new information for me. Well, my armature was dead. Not even a single spark. A new armature should be arriving by Friday and hopefully I'll be back on the road by this week-end.....

Basically, although "technically" my first simple test of the armature showed no short where there shouldn't be any and all the wiring intact, the true "growler" test showed I had a tired worn-out armature. Hope this helps anybody in the future. For me it's been a few weeks of running around in circles, jumping from armature, to field circuit to voltage regulator and then back to the armature. I also ran around the local towns here and spoke to four or fine different mechanics, grudgingly getting a word out of them here and there. And in truth, even the "pro" with the growler was a bit stumped because his initial continuity test of the armature made him think it was good too. So then he thought my field circuit was shorting out. When that checked OK he went back to the armature and put it on the "growler" and gave out the final verdict. This electrical "challenge" has been an interesting voyage for me so although I think I finally know what's going on a piece of me is still alert for something else unexpected.....I'll post the final outcome. PS. I got lucky with that one shop where I bought the mechanical voltage regulator for $30 thinking that's what I needed. They'd just hired a new very young employee who did take the part back because the packaging was so old, although there are no returns on electrical parts. JackMO!

Post Reply

Return to “Electrical”