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Author Topic: Fluctuating Voltage -Need some help!  (Read 9185 times)

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bikerboy53

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Fluctuating Voltage -Need some help!
« on: July 11, 2015, 09:13:06 PM »

My 2010 CVO Ultra Classic has been experiencing fluctuating voltage recently and I haven't been able to track down the problem. It may have started after I had the battery replaced at a local independent shop, but I don't think it is related.

When I start the bike, the voltage goes right up to about 14 to 14.5 volts and stays steady as long as the rpm's are above about 2,000. After riding 15 to 20 miles or so, the volt meter starts to fluctuate, and the longer I ride it the worse the needle swings. The stock gauge fluctuates rapidly between about 13 and 16 volts. Since I didn't trust the gauge, I taped a digital volt meter (DVM) to my gas tank to check it out, but the DVM showed similar behavior. With the DVM the voltage starts out steady at about 14.3 or so, but then once the fluctuations start the "average" reading starts to drop down into the 12 volt range with excursions as low as about 9 volts.

I have tried 3 different regulators, replaced the stator and rotor, and checked for broken wires, shorts, loose connections, etc. I even tried a different battery to see if that might be causing it, but so far no luck. All the parts I replaced tested OK according to the tests in the Electrical Manual for my bike, so I'm not too surprised that the new parts didn't make any improvement.

It seems like the fluctuations start after the battery reaches full charge. I tested this theory by putting it on the Battery Tender until it was fully charged and then taking it for a ride. Starting with the fully charged battery seems to reduce the amount of time needed for the voltage fluctuations to begin. So far it hasn't stored any codes either.

Has anybody run across this kind of thing before, or have any ideas? Is there anything besides the regulator that may have control over the charging system voltage? I’m hoping someone out there has experienced something like this before and has some good ideas…
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Para Bellum

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Re: Fluctuating Voltage -Need some help!
« Reply #1 on: July 11, 2015, 09:44:40 PM »

Ouch.  Each time I think of something that could be causing this problem, you've already checked or replaced it.  The only thing I can come up with is that something in the wiring is making a bad connection when it warms up.  One question:  You said cold voltage is steady above 2k rpm; what does cold and warm voltage do below 2k rpm?
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bikerboy53

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Re: Fluctuating Voltage -Need some help!
« Reply #2 on: July 13, 2015, 03:20:56 PM »

DoubleCoppers,
At idle or low rpms, the voltage drops down to battery voltage or a little higher. If I pull over to the side of the road when the voltage has been fluctuating, the voltage will return to "normal" as I stop. At that point I can rev the engine and the voltage goes back to 14.5 or so and is steady. Once I get back on the road and ride a couple of miles, the fluctuation starts up again. It's like there is enough drain on the battery from my cooling fans, lights, etc. to bring the battery charge down enough (when the engine is idling) as I'm coming down from highway speed that the charging system has to go back to work for a little while to charge the battery up again.

Twolanerider,
Thanks for the idea about the battery cables. I will definitely check them next weekend. Your idea got me to thinking about other wires/grounds in the system. So far (in addition to the new rotor, stator, and regulator) I have checked the wiring from the regulator to the main harness, both "dirty" and "clean" grounds, battery connections, and I have checked the engine ground. You got me to thinking that maybe another ground elsewhere might be causing the problem. Maybe I've been too focused on the charging system and related wiring when the problem might be someplace else.

Thanks guys!
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Re: Fluctuating Voltage -Need some help!
« Reply #3 on: July 13, 2015, 08:42:45 PM »

Reminds me of two previous situations:  On the stator, one phase of the 3-phase charging system was burnt out, so total output was too low, especially at low rpms (under 2500).  Charging system output wasn't keeping up with demand, and when a high-draw load (heated seat or heated liner, for example) turned on, the voltage gauge would drop to battery voltage.  The problem with the stator eventually burnt-out the voltage regulator, causing no charging and then dead battery.

Since you've replaced the stator and rotor (new regulator afterward?), it's unlikely the stator is the problem.  Still thinking wiring.  Be sure to check continuity while bending and flexing the wire and the connector; have found breaks under the (undamaged) insulation that have been the culprit.
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bakon

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Re: Fluctuating Voltage -Need some help!
« Reply #4 on: July 16, 2015, 08:40:37 AM »

You are not going to believe me and I didn't believe it either.....front wheel bearings.

The 2010 and up all have weaker bearings. My 2010 had same problem at 24k miles and four years old. I chased it all summer. Bungied meters to tank, taped meter to windshield, reading back of meter and battery directly...couldn't see a problem (unlike you, but I think its the same) problem is those digital volt meters are too slow, yours might read faster but still think its wrong reading as your bike still starts and runs ...right???
you need an oscilloscope, but still why the bearing???I looked at the light wire to fender tip being an induced voltage from abs bearing- WRONG- I believe its just vibration BUT my problem only showed its head after 10 miles of highway riding. Mine was actually the non-abs bearing bad, and just slightly....why ? who knows...but I chased it all summer and one posted put "check your wheel bearings...think I had one do that" so I did and it fixed it. Pull wheel and run bearing with finger, any bumpiness or grit? then bad...

At least this was my problem with same symptoms, been waiting to see more...I changed meter, battery, but got the reply, so never went as far as you to regulator or stator...I was trying to figure which one first...

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bikerboy53

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Re: Fluctuating Voltage -Need some help!
« Reply #5 on: July 16, 2015, 03:14:48 PM »

Bakon,
Thanks for the idea. I agree that it sounds strange, but I know a couple of friends who have had their front wheel bearings fail badly on this vintage of bike. So far mine have seemed OK. But maybe one or both of them has a problem.

The bike is going in the shop tomorrow for a service, so I'll ask them to check the wheel bearings. Or better yet, maybe I should just replace them...  :-\ I've already thrown a bunch of parts (money!)  :(  at this with no results to speak of, not to mention the amount of time I've spent troubleshooting it, so a few bucks more for front wheel bearings seems like small potatoes at this point! With all the stories about bad bearings out there, a new set will at least give me a little peace of mind for a few miles! Maybe... :'(
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Re: Fluctuating Voltage -Need some help!
« Reply #6 on: July 16, 2015, 03:26:59 PM »

I bought tools and did it myself, but think bearings were about $50-70 total. One cost more (abs). Tools cost me about $150, then some time.
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bikerboy53

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Re: Fluctuating Voltage -Need some help!
« Reply #7 on: July 20, 2015, 03:22:24 PM »

Will,

Thanks very much for the tip!!! I picked up a set of front wheel bearings on my way home to Oregon (from work in California) for a little under $60 including California sales tax. The old "plain" bearing was just a little rough feeling, but the ABS encoder bearing still felt OK. Just to be on the safe side, I replaced them both, and now my voltmeter is back to nice and steady at just a little over 14 volts.

Unless it's something like static discharge or something like that (rough bearing doesn't provide a continuous ground and allows static electricity to build up?) I don't know how a bad wheel bearing can cause an electrical system problem.

Very bizarre, but I'm very happy it's fixed! Thanks again for the tip!

After getting the bike fixed, my wife and I took it on a shake-down run to confirm that the problem really was solved, and then a new problem popped up. My driving lights and cruise control started losing power intermittently. That one was fairly easy to diagnose though compared to the voltmeter fluctuations. It turned out that HD pigtail I added to allow the driving lights to operate while the high beam is on had developed a problem. The female side of the power lead connection in the 12 place connector wasn't making good contact with the mating pin.

I was able to find the problem fairly easily by removing the outer fairing and moving the wiring harnesses around with the key switch in the on position. It didn't take long to find the connector that caused the lights/cruise to lose power and then a few minutes of futzing to figure out what was wrong. All I had to do was take the socket out of the plastic connector body and carefully squeeze it with a pair of needlenose pliers to tighten its grip on the pin a little. If that fix doesn't last, I can replace the connector fairly easily because I bought a pair of connector crimpers a few years ago. (Very handy tool to have!)

Hope I'm done with electrical problems for awhile...  :huepfenjump3:
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bakon

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Re: Fluctuating Voltage -Need some help!
« Reply #8 on: July 21, 2015, 08:24:30 AM »

I worked on missile fire controls in the Army and still don't know why the bearing causes it except for a cheap gauge which bounces and only reads and average orf what it receives. Why would they do that, because otherwise it would have a bouncing, jerky display all the time as voltage moved around with rpm, loads and battery status. I think they filter the input once it is received by gauge. An internal circuit to delay the needle moving so its nice and slow moving, makes it look stable and gives the rider a more pleasant view. It goes down slow under load when not running, like sitting there and turn on radio or amp, or driving lights, the meter slowly falls from 12 to 10 or even 8 if starter is thumbed. But in actual voltage this happens fast, so got to be a capacitor or diode just slowing the display down. 
Just my opinion.   The bearing is causing bounce which isn't electrical at all, just shaking the chit out of it and it slowly falls lower and lower, bouncing as it does. Mine needed highway speed to cause anything unusual. Less than 60 and stop/go it was fine.
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Will

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Re: Fluctuating Voltage -Need some help!
« Reply #9 on: July 21, 2015, 08:52:43 AM »


Since the same fluctuations occurred when he used a DVOM, I doubt it's just the cheap crap Harley gauge.  It sounds like whatever is happening is actually affecting the voltage, and not just shaking the gauge.  I have heard of this wheel bearing thing before, and I still haven't figured out what is actually happening.  One other thing I would recommend for anyone else seeing strange gauge behavior is checking the ground wire at the steering head area (upper fork bracket, usually on the left side).  Poor grounds can cause all sorts of strange behavior.

I'd like to see what happens if anyone has this issue and they attach an old analog voltmeter directly to the battery, instead of a digital version.

Anyhow, glad it's fixed, and glad bakon remembered this.  It could have become a real expensive headache if one of the "just replace parts until we stumble on the cure" places had gotten hold of the bike.

Jerry
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Re: Fluctuating Voltage -Need some help!
« Reply #10 on: July 21, 2015, 12:10:31 PM »

I don't think it's a cheap crap gauge. I think it's designed not to be an analog gauge relativity or sensitive as one. More of a general display and give an average reading so as to not alarm the rider. A dumbed down circuit for average use of sorts. I tried messing with any wire which could induce anything from front end. Thing is mine was not the abs bearing. So why?  In electronics we called it FM. F ing Magic
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Will

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Re: Fluctuating Voltage -Need some help!
« Reply #11 on: July 21, 2015, 01:45:37 PM »


I'm sure you know more about electrical and electronics than I do, but while some gauges are designed to be "damped" so the display isn't constantly changing (like fuel gauges in cars for instance), I've seen no evidence of that being the case on a Harley voltmeter.  If there was something in the gauge circuit to create a damping affect, it wouldn't affect a gauge that's wired directly to the battery terminals.  In his situation, not only did the voltage reading bounce around, but it dropped from approximately 14V to 12V as time went by, on the dash gauge and on his DVOM that I assume was installed across the battery terminals. 

I've scratched my head over this in the past when people have mentioned it, and couldn't come up with a solid reason why a wheel bearing would cause this.  Of course your experience and bikerboy53's experience, along with those who mentioned the same thing in the past, shows that a wheel bearing does in fact cause this weird behavior.  Like you said, F'n Magic. 

Your post not only saved bikerboy53 from pulling his hair out and possibly wasting a lot of money on electrical system parts, but it sounds like it also helped him find a bearing that was about to fail.  Well done. :2vrolijk_21:

Jerry
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