28 amp alt overcharging ?

[FWTBT]

I'm about half way from British Columbia Canada to TexSToc and I fear my system may be overcharging. I have a 1994 st1100 with the original 28 amp system. I replaced the battery in Salt Lake City. It was just not holding a charge anymore. I am unsure how old the battery was. I am getting 15.2 volts at an idle consistently and it doesn't increase with increased rpm. For those experts out there do you think my system is overcharging and cooking my battery. This is a little unsettling in the middle of a long trip. I'm mostly camping and posting this from my phone when I find wifi hotspots so my replies will be sporadic. Any advice will be appreciated.

 

[Avtrician]

That is too high. At about 2000RMP, the out pout should be 13.8 to 14.2 Volts. I guess its time to check/replace the regulator.

 

[dwalby]

That is too high. At about 2000RMP, the out pout should be 13.8 to 14.2 Volts. I guess its time to check/replace the regulator.

I had the same thing happen to me many years ago with a different bike. The problem turned out to be corrosion in the main wiring harness connector. The corrosion was causing a voltage drop across that connector, which then fed into the part of the circuit that monitored the voltage for feedback to the regulator. Since there was an unexpected drop across that connector (something like 0.7-1.0V), the voltage being sensed by the regulator was artificially low, so it was boosting its output to a range similar to yours, just over 15V at the battery. And yes, my battery was getting cooked because of the high voltage, but I made it through a 9-day trip intact before finding and fixing the corrosion. It also possible you have a bad regulator, as I'm not familiar with the 28A reliability, but its possible your regulator is fine and you just have the corrosion problem.

 

[FWTBT]

Thanks for the quick replies. Gives me some ideas to think about. I'm kind of in the middle of nowhere right now so I'm a little afraid of pulling connectors apart for fear of the unforeseen happening. I think I'll adjust my route a little and head for Roswell today and look for a motorcycle shop first thing Monday morning.

 

[dwalby]

I think I'll adjust my route a little and head for Roswell today and look for a motorcycle shop first thing Monday morning.

FWIW, in my case the mechanic at my local shop was 100% convinced I had a bad regulator and told me to buy a new one, so be wary of m/c shops troubleshooting electrical problems. Since the voltage I was seeing was technically still within the factory specs for the regulator, but at the far upper limit, I chose to investigate a bit further, and that's when I found the corroded connector problem. The regulator was good, as soon as I removed the corrosion it dropped back down to 14.3V.

Until you can verify the voltage the regulator is sensing is not being corrupted, changing the regulator is basically expensive guesswork. In my case the bike was only a few years old, so it seemed unlikely that the regulator would fail that soon, so that motivated me to look further. Given the age of your bike any failure mode is probably possible, but I'd look for conclusive proof before swapping out the regulator. Also, if yours has failed, another option would be to replace the 28A with the 40A alternator if you plan on keeping the bike for a few more years.

 

[chriSTopher]

other than the electrical issue, how are you enjoying the trip Dave?

 

[tkhelm]

I've been dealing with a 28amp alternator/VRR problem, too, although my problem was low voltage rather than high, resulting in stalls and dead batteries. I took it in to my local dealer who told me both the alternator and VRR were bad and needed to be replaced...to the tune of about $1800 for parts/labor. Before committing to that, or more likely tackling a 40amp alternator upgrade on my own, I tried to eliminate all of the other possible problems. It appears that I have completely solved the problem by investing less than $10 in a can of QD Electronics Cleaner at the local auto parts store. I opened up each of the wiring connectors that are behind the left side tupperware panel and gave them a spray on both sides of the connection, and where I could I wiped them off. Whaddayknow, my voltages at all RPMs have gone back to normal! I'm not too happy with the local dealer for not doing this before recommending such a major operation at such high cost.

I'm still road testing to be sure that the problem is really solved but if so my next step will be to go back and apply di-electric grease to those connections to prevent future corrosion.

 

[FWTBT]

Thanks for the input. I'll do that connector clean up when I get home. Sounds like that might be a good idea even if you are not having problems. I got a hold of the previous owners mechanic who knows the bike really well. He told me the battery was old and likely needed replaced anyways. He said even though my voltages are little higher than he would like to see it shouldn't hurt the gel battery I put in and to just enjoy the trip. So that's what I'm going to do. I'm going to stay away from the shop and head down the hiway. Other than this little hiccup the trip has been great. These st's are quite the machine, 20 years old, 100,000 kms and it just purrs along all day. It is a little hard to keep upright at times but I'll save that for "tip over tales" later!

 

[Brant]

Thanks for the input. I'll do that connector clean up when I get home. Sounds like that might be a good idea even if you are not having problems. I got a hold of the previous owners mechanic who knows the bike really well. He told me the battery was old and likely needed replaced anyways. He said even though my voltages are little higher than he would like to see it shouldn't hurt the gel battery I put in and to just enjoy the trip. So that's what I'm going to do. I'm going to stay away from the shop and head down the hiway. Other than this little hiccup the trip has been great. These st's are quite the machine, 20 years old, 100,000 kms and it just purrs along all day. It is a little hard to keep upright at times but I'll save that for "tip over tales" later!

I'd still pop off your seat, left-side case and left tupperware panel, unplug that VR plug-in and make sure those contacts are clean first and lather them up with dialectic grease and plug it back in. At that charge rate, chances of the all important smoke coming out the left-side tupperware before you get home is fairly good. May save from a fried regulator. Other than being able to add MORE hi-amp drawing farkles to bike with the 40amp set-up, being better than the 28amp set-up is rubbish. Anyone who's done the swap, at some point or other, whether they actually knew it or not had bad connecter or grounding issues on their existing system.

 

[FWTBT]

I'd still pop off your seat, left-side case and left tupperware panel, unplug that VR plug-in and make sure those contacts are clean first and lather them up with dialectic grease and plug it back in. At that charge rate, chances of the all important smoke coming out the left-side tupperware before you get home is fairly good. May save from a fried regulator. Other than being able to add MORE hi-amp drawing farkles to bike with the 40amp set-up, being better than the 28amp set-up is rubbish. Anyone who's done the swap, at some point or other, whether they actually knew it or not had bad connecter or grounding issues on their existing system.

This may sound like a dumb question but is that the large plug with the 30amp main fuse?

 

[BuddingGeezer]

I'm about half way from British Columbia Canada to TexSToc and I fear my system may be overcharging. I have a 1994 st1100 with the original 28 amp system. I replaced the battery in Salt Lake City. It was just not holding a charge anymore. I am unsure how old the battery was. I am getting 15.2 volts at an idle consistently and it doesn't increase with increased rpm. For those experts out there do you think my system is overcharging and cooking my battery. This is a little unsettling in the middle of a long trip. I'm mostly camping and posting this from my phone when I find wifi hotspots so my replies will be sporadic. Any advice will be appreciated.

I rode 40K miles with a 15-15.2 volts on a Datel meter with no problems '91 ST 28amp. Battery lasted 6 years and only burned one headlight bulb. Eventually my voltage increased to over 16V due to low voltage at the black wire on the VR/R, caused from line loss and age(I guess). A By-pass relay at the VR/R black wire brought the voltage down to mid 14. 15 Volts is the upper limit according to the Honda service manual. When you get the bike home check the voltage on the black VR/R wire. I'll bet it's 12v or lower.

Finish your trip.

 

[FWTBT]

Got settled into a motel last night and this morning I pulled the what I think is the VR plug apart. It looks like new. I didn't want to fiddle with things too much for fear of causing a new problem. Even though it doesn't really need it ill clean and dielectric grease it anyways when I get home.

 

[FWTBT]

This is a shot of the other half of the plug.