Light Circuit Dropped Voltage
Thread Starter
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Cruiser
Joined: Jun 2015
Posts: 104
Likes: 2
From: Olympia, WA
Light Circuit Dropped Voltage
Trying to chase down the gremlin in my '75 FXE, with custom wiring. When idling without the lights switched on I get a steady 14.2 volts at the battery. Once I switch them on I'm lucky to get 12. Increasing the rpms doesn't do much of anything to increase it either.
I checked my battery after riding last night and sure enough it is down to abt 11v. It's a newer Drag Specialties high output battery. The light isn't dim when it is on, but I could tell by the sluggish starter (after it wouldn't kick over) that the battery was low.
I have basically this same wiring setup, other than I don't run a horn or dimmer, and I have a Dyna2000i instead of a crane ignition.
I've checked continuity of the light fixtures to the frame and ground posts. Everything is under 0.3 ohms, usually 0.1. So taillight, headlight, brake switch, 30A breaker.
I'm running 16ga wire for the connections, larger for power from Battery to breaker, starter, and ground.
I'm not sure where else to start looking for such a big draw on the circuit. I was going to pull off the ignition switch next, since its just a cheap V-Twin one and see if maybe something is loose or pinched.
Thanks for the help. Here's a picture of my shovelhead as it sits now.
I checked my battery after riding last night and sure enough it is down to abt 11v. It's a newer Drag Specialties high output battery. The light isn't dim when it is on, but I could tell by the sluggish starter (after it wouldn't kick over) that the battery was low.
I have basically this same wiring setup, other than I don't run a horn or dimmer, and I have a Dyna2000i instead of a crane ignition.
I've checked continuity of the light fixtures to the frame and ground posts. Everything is under 0.3 ohms, usually 0.1. So taillight, headlight, brake switch, 30A breaker.
I'm running 16ga wire for the connections, larger for power from Battery to breaker, starter, and ground.
I'm not sure where else to start looking for such a big draw on the circuit. I was going to pull off the ignition switch next, since its just a cheap V-Twin one and see if maybe something is loose or pinched.
Thanks for the help. Here's a picture of my shovelhead as it sits now.
Road Warrior
Joined: Aug 2008
Posts: 1,306
Likes: 865
From: Sheboygan, WI
The charging systems on these old bikes weren't meant to power more than what came on them stock. Doesn't look like it at first glance, but did you add something that would add to the load on the charging system? If not, it sounds to me like your stator is showing early signs of failure. Check out the charging system.
HDF Community Team
Joined: Dec 2005
Posts: 5,421
Likes: 2,621
From: NC USA
Agree. Sounds like the charging system isn't up to snuff.
Here's a long, but otherwise excellent write up on steps to check it throughly;
https://www.hdforums.com/forum/evo-c...ng-system.html
Here's a long, but otherwise excellent write up on steps to check it throughly;
https://www.hdforums.com/forum/evo-c...ng-system.html
Thread Starter
|
Cruiser
Joined: Jun 2015
Posts: 104
Likes: 2
From: Olympia, WA
The charging systems on these old bikes weren't meant to power more than what came on them stock. Doesn't look like it at first glance, but did you add something that would add to the load on the charging system? If not, it sounds to me like your stator is showing early signs of failure. Check out the charging system.
I'll go through the steps in the link and see if I can get more info to work with. I certainly could've done something wrong on the install to keep it from working right. Just strange that a newer charging system will work so well otherwise.
i don't have any accessories or oddball attachments. the only deviation from the diagram above (which is the same setup I followed on a '96 evo chopper project and it's ran fine that way for 6 years now) is that I use a basic momentary switch mounted below the battery box as a starter button.
Thanks, really looking forward to sorting this out before the weather here in WA gets nice.
HDF Community Team
Joined: Dec 2005
Posts: 5,421
Likes: 2,621
From: NC USA
Check the connection your regulator output is tied to. It needs to be on the load side of the main breaker. Insure the regulator body is well grounded to the frame.
Also check across that breaker for resistance (no power) and for voltage drop across the posts under load. (power connected, lights on).
Should be basically zero ohms across it with no power and no more than .1 - .3 volts drop under load.
Also check across that breaker for resistance (no power) and for voltage drop across the posts under load. (power connected, lights on).
Should be basically zero ohms across it with no power and no more than .1 - .3 volts drop under load.
Seasoned HDF Member
Joined: Nov 2006
Posts: 12,878
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From: la la land jerzey
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Seasoned HDF Member
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From: Honah Lee
My guess is you have a stator problem. What I don't understand is how you have that much voltage at idle. A 2000 rpm is a modern check.
Forget lights off. Always run them on. Could be battery. It will affect voltage regulator but usually, its then too high.
If alternator resistance and AC out put is OK, you need to check resistance on all thur lines to lights.
I would have to do too much homework to verify wire size. I assume that is correct. Interesting, I have converted a couple 6 volt system to 12. I had one person tell me a wire can be too big. Not sure within reason if that's true. You don't want a 2 gage battery wire going to a tail light but would a #10 matter? Got me.
Forget lights off. Always run them on. Could be battery. It will affect voltage regulator but usually, its then too high.
If alternator resistance and AC out put is OK, you need to check resistance on all thur lines to lights.
I would have to do too much homework to verify wire size. I assume that is correct. Interesting, I have converted a couple 6 volt system to 12. I had one person tell me a wire can be too big. Not sure within reason if that's true. You don't want a 2 gage battery wire going to a tail light but would a #10 matter? Got me.
Last edited by Jackie Paper; Mar 17, 2021 at 05:51 PM.
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Stellar HDF Member
Joined: Apr 2016
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From: Masshole
Check the connection your regulator output is tied to. It needs to be on the load side of the main breaker. Insure the regulator body is well grounded to the frame.
Also check across that breaker for resistance (no power) and for voltage drop across the posts under load. (power connected, lights on).
Should be basically zero ohms across it with no power and no more than .1 - .3 volts drop under load.
Also check across that breaker for resistance (no power) and for voltage drop across the posts under load. (power connected, lights on).
Should be basically zero ohms across it with no power and no more than .1 - .3 volts drop under load.
HDF Community Team
Joined: Dec 2005
Posts: 5,421
Likes: 2,621
From: NC USA
I would never wire one that way.