I have a 2005 Road King Custom that I need a little help with... I have been having some electrical problems that I did not know about until riding the bike at night. While going down the road my headlight would suddenly dim to about 25% and slowly come back up to 100% over about a 15 second time frame. It would stay at 100% for a few seconds and then suddenly drop back down to 25% and again slowly come back up to 100% over about a 15 second period.

Tonight I took the bike up to autozone and had someone there load test the battery and they told me that there is a dead cell. He very well may be right but for one he did not look overly confident while setting up their tester and two I would like to check the other parts of the system to see if there are problems (which I think that there are).

I got home and put a multimeter on the batt with the bike off and got 12.8 V. Then I started the bike up and slowly rolled the throttle to see if the voltage went up on the bike, which it did. It went up to around 14.7 V and then the lights dimed and the voltage on the batt dropped to around 8 V and slowly worked back up to 14.7 or 14.8 V and then again the lights dimed.

All I know about the charging system is that there is a stator and regulator. I pulled the plug off the front side of the reg and tested to see if I got any current with the negative lead from the multimeter to the neg terminal of the battery and touched each of the two spots of the plug side (Circled in Red in my pic) and got about .5 V on each of them. Then tried from the neg terminal of the batt to each of the 2 spots on the reg side (Circled in green) and got 12.8 V on each. I have no idea if that would tell me anything or not. I would assumed that the reading I am getting from the reg side (Green) is just a straight line to the batt so that reading is probably what it is supposed to be, but that I should not be getting any reading from the plug side (Red). Again I have no idea which I why I am here asking for help. So any guidence you can pass my way for how to check the stator and reg would be appreciated.



I was guessing that the reg is bad because the batt appears to be getting to much juice, but just a guess...

Probably all 3 things (Stator, reg and batt) need to be repalced.

Thanks
Phil

 

It's been a lot of years since I worked on these things and electrical was never my strong suit. That having been said, I would suspect the Regulator is bad.

 

Thanks IA! From what I have read if you have a bad regulator it can cause the stator to burn up? I think that is correct anyway. I have been reading so much about this over the past few days I'm having a hard time keeping it all straight. So if the reg is bad there is a good chance that the stator is bad or getting bad. If I would replace just the reg and the stator goes bad it will fry the new reg? Again, I am asking here, since I do not know.

My assumption is that it is best to replace both.

From what I have been reading Cycle Electric seems to be the choice most go with. But I am still looking for choices there too.

Thanks again.
Phil

 

Have you checked your grounds? It very well could be a loose or corroded ground.

 

I have not done that... Very simple step I did not even think about. Thank you, I will go out and do that in a little bit.

Phil

 

The bikes a 2005, if that's the original battery, it's what, 6 years old. Replace it.

 

The batter was replaced in July of 2007. So it is near the end of its life anyway. So if anyone wants to throw out recomendations for a new batt that would be great too.

Phil

 

I doubt your battery has a bad cell, if it did you'd never get much more than ten volts out of it and it would never start the bike.

As for the voltage regulator the newer ones like you have are all solid state rather than mechanical, so it's not a slam dunk it's the regulator. (Although sure, they can still go bad.) And sometimes it's not enough the regulator is grounded via its mounting bolts. So running a extra ground wire from a regulator case bolt to a solid frame ground is a good practice. Also, in general, modern electronics either work or they don't, and when it's a matter of being intermittent (like your voltage drop while revving the motor) it's more likely a wiring issue, either a loose connection, or a chaffed wire dumping output voltage to the frame due to vibration. But the first place to start looking is grounding issues. Without a solid ground the voltage regulator can't send a steady voltage to the battery.

It may helps to think about what a voltage regulator does. On on Harley it's really a voltage regulator/rectifier. Your rotor/stator produces AC current, but your bike has no use for AC current so the voltage regulator changes that AC current into DC current via its rectifier. It also regulates the amount of voltage going to your battery (usually about 13.5 volts) by turning any excess voltage into heat and passing it through the regulator case fins as heat. (And why, in my opinion, chromed regulator cases or mounting a regulator outside the airflow, are at odds with a regulators design purpose which is to dissipate heat.)

Try following every inch of wire from the voltage regulator to the battery looking for damage and/or loose connections.

 

Great info, thanks Nick. I have to work late tonight and then will be gone all day tomorrow, but I will check it out as soon as I can.

I did check the grounds that are in front of the battery and they where a little rusty on top so I took the nut off and hit them with a wire brush. That did not make any difference in how everything operated but at least they are clean now. From what I have been reading on this and other forums it seems that a lot of people have this problem anywhere between 18,000 and 25,000 miles and my bike is around 21,000. Of course you only hear about the ones with problems but it still seems to be quite a bit.

It would be awesome if it was just the wiring!

Phil

 

Just by the symptom you are having, it sounds like your charging system circuit breaker is opening/closing ....

There are two wires coming out of your regulator, one goes to ground, the other ( the 'hot' wire ) will or should go to a circuit breaker before it gets to your battery.

As NickD says, do check your Reg for a good ground and ensure continuity in your circuits.

If your battery will start your bike easily, I wouldn't look at that as a source of your problem.