Charging System Help

[Andrew Shadow]

I take voltage readings every spring when I fire up my ST1300. The voltage drop when you are starting the engine seems quite normal but I have never seen voltage readings as low as what you have reported when the engine is running. I have never seen less than 13.9 V at idle, and at anything above idle I always see 14.2 V or above. If the battery is good, and if there is not a wiring problem (e.g. loose connections, corrosion, etc.) I fear that you have an alternator problem. Unfortunately if it is only the voltage regulator it is about the same amount of work as if it was the alternator.

It isn't still under warranty from Michael? (Kidding of course.)

 

[dwalby]

I have never seen voltage readings as low as what you have reported when the engine is running. I have never seen less than 13.9 V at idle, and at anything above idle I always see 14.2 V or above. If the battery is good, and if there is not a wiring problem (e.g. loose connections, corrosion, etc.) I fear that you have an alternator problem.

I don't have a lot of experience with failed alternators (fortunately!) but back in the old UJM days when I had a failed alternator it shorted out completely. Just curious if alternators typically fail altogether like my experience, or if there are varying degrees of failure that might explain the OP's situation.

 

[Andrew Shadow]

I don't have a lot of experience with failed alternators (fortunately!) but back in the old UJM days when I had a failed alternator it shorted out completely. Just curious if alternators typically fail altogether like my experience, or if there are varying degrees of failure that might explain the OP's situation.

The ST1300 has an automotive style alternator so the failures can be the same.
e.g. The failure can be the voltage regulator, the diode set, the brushes, the rotor windings, the stator windings, as well as mechanical failures like bearings.

The problem with the ST1300 is that considering the effort to get it out and back in many people opt to replace it rather than to risk the failure of another aged and possibly tired component later on.

 

[Andrew Shadow]

To add to my above response what I forgot to include, and in answer to your question, is that in my experience the most common failures with this type of alternator are the voltage regulator and the diodes. Unfortunately, as I previously stated, getting to those requires removing the alternator.

 

[JamieE]

Thanks @Andrew Shadow ! I read through the service manual and the work involved is out of my league. I’m going to try to find someone local to help. Is rebuilding it an option? Here in Canada I’m looking at over a grand for a new one (not sure how new).

 

[Andrew Shadow]

Rebuilding it is no different than rebuilding an automotive alternator. All of the parts are listed in the parts diagram individually. If they are ALL still available and how many might be back order is something that you will need to check in to with your favourite parts supplier.

If this is something that you don't want to tackle yourself any alternator/starter motor repair shop can easily do it. The problem with finding somewhere to rebuild these is not the complexity of it, it is not much different than an automotive alternator of the same era. The problem is that they all have test rigs designed for automotive alternators that have a pulley on them. Consequently they can not put it on their test bed. Because they can't test it most don't want to bother with it. Adapting something to allow them to spin the alternator on their test bed is not an insurmountable obstacle but it is not worth the effort for them in order to be able to test and rebuild one alternator, so they just say that they can't do it. If you are willing to pay for their time and energy to do this you might find a shop that is willing. One of those scenarios where you never know until you ask.

If you find an automotive place that is willing to do this you may also have to supply them with the parts because they may not have a relationship with any motorcycle parts departments, but that is not an issue once they tell you what they need.

It might well be worth your while to ask on here if anyone knows of somewhere who will do this. I remember at least one thread where a member on here found a shop that adapted their test rig so that they could repair and test it but I have no idea who that was. I have never looked for one bit it seems to me that there must be shops somewhere that rebuild motorcycle alternators.

 

[vstrom.zrxdude]

If you had bad alternator, battery you wouldn't be able to crank engine over with starter motor when it quit ,I think you need to get your mind on a different path to solve this problem

 

[Larry Fine]

Start with comparing the meter to a known-accurate meter, and/or on another motor vehicle.

 

[Andrew Shadow]

I just saw your video. Before you go taking anything apart something doesn't make sense. Are you sure that your voltmeter is good? Those readings not only don't make sense they are all over the place. I don't know for a fact but I highly doubt that it would even run at 6V and less. That just isn't enough voltage to power the ECM, the fuel pump, the ignition, etc., so those readings seem suspect. Before proceeding I would make sure that your voltmeter is good. Bad tools lead to bad diagnostics, which leads to unnecessary repairs. Make sure that you have voltage readings that are accurate before you start any major repairs.

Out of curiosity, has the digital clock ever reset on you? I know you had the battery tested but this is an early warning of a failing battery.

 

[JamieE]

I just saw your video. Before you go taking anything apart something doesn't make sense. Are you sure that your voltmeter is good? Those readings not only don't make sense they are all over the place. I don't know for a fact but I highly doubt that it would even run at 6V and less. That just isn't enough voltage to power the ECM, the fuel pump, the ignition, etc., so those readings seem suspect.

100%! I was trying to do everything myself with a multimeter which obviously didn't work out very well so I bought a digtial USB charger which shows the battery voltage.

Bike off --> 12.9V
Starting bike --> drops to 10.4 and then up to 13.6 (idling at 1.5k and not at temp)
Bike gets to temp --> 13.8V (idling at 1k)
Rev to 5k --> 13.8V
Turn headlights on --> drops to 12.3V/12.7V.

Out of curiosity, has the digital clock ever reset on you? I know you had the battery tested but this is an early warning of a failing battery.

At the border the clock reset which lead me to believe something was wrong with the battery but it tested fine....

 

[oude geit]

My 1300 has voltage from 12.5 to 14 its a constant variable by usage and the regulator function. New alternator and the same variables......it's only been like this for 160000 miles. So looks normal to me.....bad battery is much easier than an alternator. Jme

 

[Andrew Shadow]

Those readings make more sense. If they are sure that the battery is good if it were me I would fully charge the battery again and use it for a bit while carrying a booster pack around with me- see what it does.

 

[JamieE]

This is what I got.

 

[Andrew Shadow]

I am not familiar with the new electronic type of battery testers, which is what this looks like, and how they work, so take my comments with a grain of salt.

Out of curiosity I would ask them to explain how they can say that it is good if they didn't test whether or not it can accept a charge, or what it's reserve capacity is. There may be a valid explanation, but I would want to know.

How was the CCA arrived at? How did they get a test result of 310 CCA out of a 230 CCA rated battery, which is the standard CCA rating for an AGM YTZ14S. That is a big discrepancy.

 

[Igofar]

The folks who claimed they tested it probably didn’t know what they were doing.
A battery tender green light means nothing in the real world.
The fact it dipped down to 10.4 speaks volumes.
Your battery is bad.
Your clock will reset to 0100 telling you it’s on its way out.
Probably nothing wrong with charging system.

 

[ST-Traveler]

The fan turned off and it was back to 13.3V. I then held the revs at about 3K and it seemed to max out at about 13.6V.

I did not read all the posts but that seems a little low for charging voltage. Mine runs beween 14.1 and 14.2 most all the time - only dipping to maybe 13.9 at idle when all electrics are drawing.
A battery under load can experience a voltage drop if not properly charging with when the bike is running. The ST has one of the highest outputs at 740 watts around 5000 RPM when compared to other bikes.
The battery will not keep the bike running very long, I would suspect your alternator is on the brink.
Under load with the bike running you should see almost no voltage drop with any accessories on like headlight high beams or horn, turn signals, etc. Now if you are running heated clothing then that can put quite the strain on your charging system, but even then a healthy ST1300 alternator is well equiped to deal with those type of strains on the system.

I just went out and tested my bike for you. I have a healthy battery and a fairly new alternator and these are my readings.
1. Turn ignition on ( accessory mode) - 14.1 - 14.0 but drops pretty rapidly to just above 12.5 V (Actual battery charge indicated on volt meter) Obviousoly all the lights come on and meter panel.
2. Crank engine - voltage drops to 11.1 V and has plenty of power to start engine immediatley on second crank.
3. After engine running jumps to 14.1 volts immediatley.
I hope this info is helpful for you.
And yes installing a new alternator is something you can do yourself just have to be patient.

 

[dwalby]

The fact it dipped down to 10.4 speaks volumes.
Your battery is bad.

yeah, previously he had reported 11v with starter cranking, which seems reasonably good, but 10.4v is getting low.

Given the cost of repair or replace the alternator, a new battery purchase might be money well spent.

OP, you never mentioned how old the battery is, if its more than 2-3 years old then its definitely money well spent.

 

[Larry Fine]

Are you measuring voltage at the battery terminals or elsewhere in the bike's wiring?

 

[Andrew Shadow]

I did not read all the posts but that seems a little low for charging voltage. Mine runs beween 14.1 and 14.2 most all the time - only dipping to maybe 13.9 at idle when all electrics are drawing.

As I wrote earlier, that is exactly what result I get from mine. Surprisingly consistent.

I have never seen less than 13.9 V at idle, and at anything above idle I always see 14.2 V or above.

My 1300 has voltage from 12.5 to 14 its a constant variable by usage and the regulator function. New alternator and the same variables......it's only been like this for 160000 miles.

I have never seen such low voltage readings. Your result is interesting as I would not expect to see that much variability. The ST1300 has an old style automotive type alternator from the time when they all ran consistently in the 14.2V range. Admittedly I have also only ever taken a voltage reading shortly after having started the engine so there is a certain amount of battery drain that has occurred to start the engine that the alternator is working to replace so the readings will reflect that.

The variance in your results has made me curious. I think that I might hook up a voltmeter that I can take on a ride with me and see what it does after then engine has been running a long while and the battery has been topped back up to fully charged.

 

[oude geit]

I have a constant voltage dash mount gauge so I see all the time. Installed because I didn't like all the variables. I can turn on my auxiliary high beams, or grips and see the voltage jump up to 14ish. Shut them off and watch it trickle back down.....idk ive never liked it but another alternator is a lot of money and it works so as I say...if it works dont fix it....