Light Circuit Dropped Voltage
Thread Starter
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Cruiser
Joined: Jun 2015
Posts: 104
Likes: 2
From: Olympia, WA
So after following some advice I have more info, still not fixed but hopefully close. Easier just to reference all your help in the quotes below:
Thanks for the help. I did as you advised. I pulled the regulator it seemed well grounded but I flapwheeled more bare metal between the mount, engine and regulator. I had the regulator straight to battery, I know another poster said to keep it on Batt. I switched it for the time being to see if any difference was made.
Breaker was at 0 ohm with no power. Voltage drop at load was -.2.
At restart after all that I did have a slight increase in voltage with lights on, but only from 12.0ish to 12.5ish
I was actually wondering about my wire size relative to charging. I can't give you an exact gauge but my wire from Batt. to breaker is 3/16" thick over the insulation. It's the same size as the wire from my regulator. I had the thought this morning that it may be too small to feed everything under load. But wiring is not my strong skill.
That's how I had it. I switched to the breaker as recommended above, but really didn't see any difference.
Thanks all. I really appreciate the expertise.
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.
Breaker was at 0 ohm with no power. Voltage drop at load was -.2.
At restart after all that I did have a slight increase in voltage with lights on, but only from 12.0ish to 12.5ish
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.
Thanks all. I really appreciate the expertise.
Seasoned HDF Member
Joined: Mar 2010
Posts: 38,526
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From: Honah Lee
You need a #10 at minimum to your breaker. Depending on voltage of insulation rating, the insulation can be twice as thick, so you don't measure twisted wire over insulation. So I have no idea what your wire gage is when you say it that way. Start at the basics. Start at the AC alternator output. You may have to contact maker for infor on that spec.
HDF Community Team
Joined: Dec 2005
Posts: 5,402
Likes: 2,605
From: NC USA
I don't think wire size is your problem and reg wire position on the breaker won't affect charging voltage at all. Do you know what size charging system you installed? There's a 22 amp and 32 amp version. Either one should do more than enough for your bike but neither will show a charging voltage much over 12.5 at or near idle with the light on. And if the battery isn't defective, it can take a long time to recover from the discharge of starting the bike.
You said you rode recently and it was down to 11 when you got back was my reason for thinking it was a charging problem. Remember, just because a battery is new doesn't mean it's good. You wouldn't believe how often a bad one turns up on here.
You can take to any "fast food" parts store and have it load tested for free. It needs to be fully charged for an accurate load test. I highly recommend you do that next, before you panic chasing an issue that may not exist. Do that and see what you have and one of us can walk you thru the stator check if the battery isn't defective.
You said you rode recently and it was down to 11 when you got back was my reason for thinking it was a charging problem. Remember, just because a battery is new doesn't mean it's good. You wouldn't believe how often a bad one turns up on here.
You can take to any "fast food" parts store and have it load tested for free. It needs to be fully charged for an accurate load test. I highly recommend you do that next, before you panic chasing an issue that may not exist. Do that and see what you have and one of us can walk you thru the stator check if the battery isn't defective.
Seasoned HDF Member
Joined: Nov 2006
Posts: 12,878
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From: la la land jerzey
Every alt bike was wired that way direct to the battery as the regulator is diode protected - unless you rap it around the exhaust and follow the correct route its never shorts
Stellar HDF Member
Joined: Apr 2016
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From: Masshole
Stellar HDF Member
Joined: Apr 2016
Posts: 3,315
Likes: 2,110
From: Masshole
Advanced
Joined: Nov 2018
Posts: 66
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From: michigan
Start the bike, put your voltmeter on the + and - terminals of the battery and see what the voltage is while running
Run it up to around 1500 - 2500 RPM. If the voltage does NOT go to 13.8-14.2 you are not charging.
If it does go that high, have your battery load tested (as has been mentioned).
If it does not go that high, its regulator / stator problem. (seems you have checked the wiring in this area).
Run it up to around 1500 - 2500 RPM. If the voltage does NOT go to 13.8-14.2 you are not charging.
If it does go that high, have your battery load tested (as has been mentioned).
If it does not go that high, its regulator / stator problem. (seems you have checked the wiring in this area).
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Thread Starter
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Cruiser
Joined: Jun 2015
Posts: 104
Likes: 2
From: Olympia, WA
I had my battery load tested after charging it up all night. It's a 310 CCA AGM battery that tested good. It dropped from 12.5 to 11.7 on a 15amp load, then back up in the recovery period.
I should mention I tested the charging system as well last night. I had no reaction to resistance testing from each regulator pin to ground. With the probes in the stator female plugs I got about 50 AC volts at around 2000 rpms.
As suggested I guess the next step is replacing the regulator anyway. Frustrating since I maybe have 100 miles on the current one. But that's what I get for riding a classic I suppose. If there are any other stones I haven't turned over I'm all ears. Thanks much.
I should mention I tested the charging system as well last night. I had no reaction to resistance testing from each regulator pin to ground. With the probes in the stator female plugs I got about 50 AC volts at around 2000 rpms.
As suggested I guess the next step is replacing the regulator anyway. Frustrating since I maybe have 100 miles on the current one. But that's what I get for riding a classic I suppose. If there are any other stones I haven't turned over I'm all ears. Thanks much.
Seasoned HDF Member
Joined: Nov 2006
Posts: 12,878
Likes: 5,449
From: la la land jerzey
Most regulators are communist china and are a lot like the toasters they sell - only works on one side of the bread
USA regulators are available from Mid USA motorcycle and worth the wait
USA regulators are available from Mid USA motorcycle and worth the wait