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Voltage fluctuations

Lobo1

Junior Member
A buddy of mine called me yesterday. He has an 05 T C. He said he noticed his headlight going dim and brightening back up the other morning on his way to work. Said his indash bolt meter would be at 14-15 volts when idling but when he gives it gas it drops to 10-11 volts. Then it quit when he was about 1/2 way to work. No more fluctuations until yesterday morning it started doing it again. Did it all the way to work and all the way back home.
I went onetime there and here's what I have checked so far:
Checked battery voltage with Fluke 87 DVOM: 12.7 volts with switch off.
Charged battery for an hour and a half at 10 amp setting on his charger. Rechecked voltage still reading 12.7 with switch off.
Started engine and checked voltage at idle (1000 RPM). Read 14.8 volts
Revved engine and voltage at battery posts dropped to 10.4 volts but immediately went back to 14.8 when went back to idle. Revved and HELD at 2000 RPM and voltss would drop back and forth from 14.8-10.4 ish constantly.
Checked ground between regulator and frame. Good (0.0 on meter)
Checked AC voltage on stator output wires: 26.8 at 1000 rpm idle, 53.7 at 2000 rpm.
That's all I checked so far. Had to get home, shower and bed. Getting late. Work today. Put his battery tender on all night and he is carrying battery to be load tested today.

Anyone ever seen this problem??

Oh yeah, he bought battery new last month. ( but that don't really mean nothing)

Any suggestions greatly appreciated.

Ride safe
 
AC voltage at stator looks good at 1k & 2K. Did you check the rotor for any grounds? I wouldn't think there would be a grounded stator with good AV output, but I would check anyway. If no grounds and battery test good then the regulator is bad.
tourbox
 
I should get off today around 4:00 ish. I am going to go back over there. I will keep everyone posted on findings
 
Good news. Shortly after I got home from work yesterday, my buddy comes pulling up on his tour classic grinning from ear to ear. When he took his battery to the national auto parts chain store he bought it from, it failed the load test miserably. They offered him a full warranty replacement since he just bought it last month. (5-5-17) or a full refund. He took the replacement to give it a second chance. Took it home, charged @ 2 amp for a couple hours, installed and no more voltage fluctuations.
Thanks for input. Didn't get to post update yesterday, we ended up going for a nice Saturday evening ride. 153 miles and Bobby said no fluctuations.
 
Good deal, thanks for the update.

THANK YOU Jeff. I used the information I got off of here to help test the charging system. I have told several folks about this site, the great folks on here and that overwhelming abundance of knowledge that is available from this site. And that knowledge is shared / made available from people like you, @tourbox and @SledDog just to name a few. Along with many others.

I know I left quite a few names out of my post ^^^^^above^^^^^ but if I named everybody I have seen that has a ton of knowledge on this site, in the short time I have been a member, it would be a very long post.
 
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