Is my Altenator shot?

[Guzinta]

This is my first post here. I've owned my 2001 ST1100 for three years and it's been awesome until mid summer this year, when one day I went to go for a ride and the battery was deader than a door nail. 100% flat. I charged it up rode it and the bike was fine for a couple of week, but then one day same thing. At this point I ordered a new battery and also started looking for shorts and also checked to fuse like to see if I needed the red wire bypass. Everything is just like new. No melting, discoloration. Contacts shiny and snug. I put the new battery in, bike ran fine for a couple more weeks, and then, yep... same thing again, completely flat battery. I charged up thr battery again aand at that point when I started the bike, I noticed that the output voltage was way high, like 18+ volts. (I have an SAE charge port with a voltage readout). It usually reads 12.7ish when bike hase been sitting a while. When the bike is running, it tops out at 14.2 to 14.4. BUT intermittently it will read very high, as I stated earlier, and I made the observation that when it's reading high and then shut off the bike, the next morning the battery is totally discharged. If it's reading 14.2 aand I shut off the bike, the battery is fine.

Questions:
1) Is it possible (intermittently) the rectifier/regulator has a short?
2) I assume, if this is my problem, the recifier is integrated in the alternator and I need a new alternator. Is this assumtion correct?
3) Is there a tutorial/instructions someone can point me to on the process of changing the alternator on the ST1100?

Many Thanks in advance! Neil

 

[dwalby]

first thing I'd do is use a real multimeter rather than your charge port voltmeter just to confirm the voltage readings you've reported.

I don't know much about the alternator internals, but I'd be surprised if it was causing an intermittent short and killing your battery. What about your charge port, is it possible that there's something going on there that's related to the battery draining when it reports a weird voltage level?

To trace down a rogue load, disconnect either of the battery leads and put a multimeter in series between the lead and the battery terminal with the meter set to current measuring mode. I think the clock draws 1 or 2 mA, anything significantly higher than that may be the cause of your battery drain. Start by pulling fuses to narrow down the location of the drain, and then start looking at wires and connectors for further clues to pinpoint the location of the problem.

 

[Guzinta]

first thing I'd do is use a real multimeter rather than your charge port voltmeter just to confirm the voltage readings you've reported.

I don't know much about the alternator internals, but I'd be surprised if it was causing an intermittent short and killing your battery. What about your charge port, is it possible that there's something going on there that's related to the battery draining when it reports a weird voltage level?

To trace down a rogue load, disconnect either of the battery leads and put a multimeter in series between the lead and the battery terminal with the meter set to current measuring mode. I think the clock draws 1 or 2 mA, anything significantly higher than that may be the cause of your battery drain. Start by pulling fuses to narrow down the location of the drain, and then start looking at wires and connectors for further clues to pinpoint the location of the problem.

Thanks for your reply.. Yes i will try to trace it out with a multi meter. I, of course, will have to wait until it goes back into a problem state. Right now the problem is nonexistent, but a matter of time before it comes back. I don't suspect the charge port, but I'll disconnect it next time it reads high and check voltage output with multi meter. the other problem is riding season is about over here in Vermont.. ugg

 

[dwalby]

Right now the problem is nonexistent, but a matter of time before it comes back.

I suspect it would be unlikely that the alternator has an intermittent short that is the source of the battery drain. Far more likely to be something in the wiring that is able to move around and periodically short out.

 

[Slydynbye]

Just FYI The regulator is a common automotive part and if it's faulty you can replace just that component. It sits on the rear of the Alternator. The Voltage Regulator is a Denso 126000-1160 I can send pictures if you like.
Now getting to it is a whole different story. Most shops replace the entire Alternator assembly because they don't want to go in there twice.

 

[Guzinta]

Just FYI The regulator is a common automotive part and if it's faulty you can replace just that component. It sits on the rear of the Alternator. The Voltage Regulator is a Denso 126000-1160 I can send pictures if you like.
Now getting to it is a whole different story. Most shops replace the entire Alternator assembly because they don't want to go in there twice.

Thanks for the info! I think if I get that deep into it, I'll just put in a new alternator. The bike only has 58000, but if I'm in there, I think I'll do what most shops do and go new.

 

[Guzinta]

*New Observation* Yesterday I went out and fired up the ST. The last time I fire it up it was in a state where it was staying maxed at 14.4 volt based on the sae read out. Even while giving it a quick rev up to 3k or 4k rpms it stayed a 14.2 - 14.4 as it should. Then I tried something I hadn't tried before. I revved it to 3k rpm and held it there. In about 5 seconds it jumpe up to 20+ volts. I know the sae charge port read out is correct. You can see the head light get twice as bright as it should when revving, as apposed to normal state the head light stays constant when revving. I'd get the multi meter on it if I could but there is no room where it's stored. I was able to disconnect the neg battery terminal so the battery doesn't drain. I'm seriously thinking the regulator has an intermittent short. If the alternator/regulator is putting out over 14.4, the battery discharges. If it stays st 14.4 (as it should) the battery does not discharge. I know I need to confirm with the multi meter, but I pretty convinced. Comments.. Ideas?

 

[kiltman]

I thought I might have a bad regulator on my old 97, given the work needed to replace the one component I bought the Chinese alternator and did the swap. In my case there was no change in my issue. Later I discovered I had a wiring issue with my PIAA lights. ( I basically did the swap for nothing, only to gain experience)
It takes about 8 hours to swap out the alternator, that said, switching out the alternator (40amp-40amp) is extremely simple and will be done in short order.
I suggest getting a new rubber boot for the swing arm as that makes assembly that much easier.
I have no insight as to what is causing your particular issue. Possibly check all the ground points. There is a ground wire in the loom that connects to a bolt holding the folding handle on the left side or it may be connected to the left pannier rail. The ground from the alternator to the frame.
Good luck in resolving your issue

 

[ST Gui]

I revved it to 3k rpm and held it there. In about 5 seconds it jumpe up to 20+ volts...

If it stays st 14.4 (as it should) the battery does not discharge.

A 20V reading is alarming to me. I don't think I've ever seen a mention here of that high of a voltage. Is your SAE charge port connected directly to the battery terminals? As the alternator voltage goes up it's amperage should fall so that may be why the battery doesn't discharge at 14V+. Even so I wouldn't think the battery would be happy getting 20V for any length of time.

More troubleshooting is required. I'd really want to look for worn wiring and bad connections before considering just replacing any bits and see if that works. Does holding the revs at 3000rpm raise the voltage every time?

 

[dwalby]

In about 5 seconds it jumped up to 20+ volts. I know the sae charge port read out is correct. You can see the head light get twice as bright as it should when revving,

interesting, it would appear that your regulator isn't doing its job correctly, as you first suggested. This type of thing is pretty rare around here, the 40A alternators are pretty reliable.

 

[kiltman]

Disconnect your SAE charge port, use a volt meter across the battery and see if you get the same results. I'm wondering if that charge port is not functioning properly.

 

[dwalby]

Disconnect your SAE charge port, use a volt meter across the battery and see if you get the same results. I'm wondering if that charge port is not functioning properly.

yeah, I had the same thought originally, but I don't think there's any way that could explain the headlights getting 2x brighter in his later post.

 

[Guzinta]

A 20V reading is alarming to me. I don't think I've ever seen a mention here of that high of a voltage. Is your SAE charge port connected directly to the battery terminals? As the alternator voltage goes up it's amperage should fall so that may be why the battery doesn't discharge at 14V+. Even so I wouldn't think the battery would be happy getting 20V for any length of time.

More troubleshooting is required. I'd really want to look for worn wiring and bad connections before considering just replacing any bits and see if that works. Does holding the revs at 3000rpm raise the voltage every time?

Yes the SAE port is directly the the +/- battery terminals. It doesn't jump voltage everytime, but eventually will jump. I took a video that I'll post if not too large. It's about 3 minutes long. The first munute or so I hold at 3000rpm at it holds at 14.3 volts. I then shut off and restart the bike and run at 300rpm again it rather quickly it jumps up to 20 volts. It's definitely not a proplem with the sae charge port. The headlight intensity increases a ton when the volts jump. Also in the video you'll notice my dash lights flickering off and on like a christmas tree. It also done this for the three years I've owned the bike and I don't think it's at all related. It is definitely time to address the problem too. It is a great running motorcycle and a joy to ride!

hmm. won't let me attach a apple quicktime .mov - 362 meg

 

[Guzinta]

I thought I might have a bad regulator on my old 97, given the work needed to replace the one component I bought the Chinese alternator and did the swap. In my case there was no change in my issue. Later I discovered I had a wiring issue with my PIAA lights. ( I basically did the swap for nothing, only to gain experience)
It takes about 8 hours to swap out the alternator, that said, switching out the alternator (40amp-40amp) is extremely simple and will be done in short order.
I suggest getting a new rubber boot for the swing arm as that makes assembly that much easier.
I have no insight as to what is causing your particular issue. Possibly check all the ground points. There is a ground wire in the loom that connects to a bolt holding the folding handle on the left side or it may be connected to the left pannier rail. The ground from the alternator to the frame.
Good luck in resolving your issue

Thanks for the pointers and tips. I will save those for when I can seriously dive into this in the spring.

 

[kiltman]

Some people actually add a ground from the headlight to the frame.

Sort of related, the cause for the instruments flickering may also indicate a bad ground

 

[ST Gui]

I took a video that I'll post if not too large.

This site does not host video. Posting your vid to YouTube and then posting a link here works really well.

 

[Guzinta]

This site does not host video. Posting your vid to YouTube and then posting a link here works really well.

Thanks for the heads up! Uploaded to YouTube...

https://youtu.be/IHF74SmYc_4

Video Description: It's about 3 minutes long. The first minute or so I hold at 3000rpm at it holds at 14.3 volts. I then shut off and restart the bike and run at 300rpm again it rather quickly it jumps up to 20 volts. It's definitely not a problem with the sae charge port. The headlight intensity increases a ton when the volts jump. Also in the video you'll notice my dash lights flickering off and on like a christmas tree. It also done this for the three years I've owned the bike and I don't think it's at all related. It is definitely time to address the problem too.

 

[mjc506]

Wild speculation - battery terminal connections (or internal broken connection?) The bike will run from the alternator (once started) but the battery provides a lot of filtering and damping. Voltages will fluctuate significantly if disconnected.

Flickering dash LEDs could've been caused by overheating during soldering, and/or by overvoltage during their life (they don't look stock)

 

[ST Gui]

 

[Sidewise]

This is my first post here. I've owned my 2001 ST1100 for three years and it's been awesome until mid summer this year, when one day I went to go for a ride and the battery was deader than a door nail. 100% flat. I charged it up rode it and the bike was fine for a couple of week, but then one day same thing. At this point I ordered a new battery and also started looking for shorts and also checked to fuse like to see if I needed the red wire bypass. Everything is just like new. No melting, discoloration. Contacts shiny and snug. I put the new battery in, bike ran fine for a couple more weeks, and then, yep... same thing again, completely flat battery. I charged up thr battery again aand at that point when I started the bike, I noticed that the output voltage was way high, like 18+ volts. (I have an SAE charge port with a voltage readout). It usually reads 12.7ish when bike hase been sitting a while. When the bike is running, it tops out at 14.2 to 14.4. BUT intermittently it will read very high, as I stated earlier, and I made the observation that when it's reading high and then shut off the bike, the next morning the battery is totally discharged. If it's reading 14.2 aand I shut off the bike, the battery is fine.

Questions:
1) Is it possible (intermittently) the rectifier/regulator has a short?
2) I assume, if this is my problem, the recifier is integrated in the alternator and I need a new alternator. Is this assumtion correct?
3) Is there a tutorial/instructions someone can point me to on the process of changing the alternator on the ST1100?

Many Thanks in advance! Neil

Slydynbye, What he said.