1972 FLH Charging Problem
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Stage III
Joined: Jul 2016
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From: Chicago
1972 FLH Charging Problem
I have a 1972 FLH fully restored with a rebuilt engine all from ground up which included a new stator and I changed the voltage regulator last year trying to fix this issue.
The motor runs great but my batt wont charge. After I ride for an hour with lights, it will run but if I shut it down it doesnt have enough batt to start. Been through 2 batterys thinking they were the issue but that does not seem to be the prob.
Seems like the stator is working but have a strange prob in the charging system. Here is the weird part, if I probe volts from pos term on batt to neg term on batt I get roughly 12.7. If I probe pos term on batt to ANYWHERE on the engine or frame I get the 13.7 that I need to charge. This is a simple system but cant figure it out what is causing this volt difference literally in the length of the ground wire. I have smooth freshly filed connection on the frame and I changed the ground wire 3 times with different materials and different ground points with solid copper on it now with no difference in meter reading. Any ideas would be greatly appreciated!
The motor runs great but my batt wont charge. After I ride for an hour with lights, it will run but if I shut it down it doesnt have enough batt to start. Been through 2 batterys thinking they were the issue but that does not seem to be the prob.
Seems like the stator is working but have a strange prob in the charging system. Here is the weird part, if I probe volts from pos term on batt to neg term on batt I get roughly 12.7. If I probe pos term on batt to ANYWHERE on the engine or frame I get the 13.7 that I need to charge. This is a simple system but cant figure it out what is causing this volt difference literally in the length of the ground wire. I have smooth freshly filed connection on the frame and I changed the ground wire 3 times with different materials and different ground points with solid copper on it now with no difference in meter reading. Any ideas would be greatly appreciated!
Club Member
Joined: Jun 2007
Posts: 45,429
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From: Bedford UK
Hi from the UK and welcome to HDF. There is a Sticky at the top of this section with instructions on diagnosing charging circuit problems. They should help you find the cause of your problem. There are also instructions in the factory service manual IIRC.
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Stage III
Joined: Jul 2016
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From: Chicago
Thanks for the welcome grbrown... I have gone through the service manual with no luck for this issue, but I will check the link to see if there is anything in there that may help with a different look.
Club Member
Joined: Jun 2007
Posts: 45,429
Likes: 2,898
From: Bedford UK
The Stickies (there are actually two) test the stator output as well as the regulator output. When charging you should be getting over 14volts at the battery terminals, engine running but lights switched off. Do use a multimeter for your checks, to get dependable results.
Club Member
Joined: Jun 2007
Posts: 45,429
Likes: 2,898
From: Bedford UK
There is a current thread here on a similar subject, which may be worth reading. You're not alone in having charging problems!
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Stage III
Joined: Jul 2016
Posts: 3
Likes: 0
From: Chicago
Thanks grbrown for the threads. I have looked them over and have leveraged what I could as some were referencing a 2 pin system and I have a 4 pin. However, the threads have given me enough info to lead me to the stator being partiall grounded to the frame. Given that I will have to tear into the guts to fix what I think to be the problem, I'm going ahead And updating the 15amp system to a 32amp system which will be a complete swap of stator, rotor, and regulator.
I will let you know how that turns out and if it fixes the problem. The help is much appreciated.
I will let you know how that turns out and if it fixes the problem. The help is much appreciated.
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