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Sprint ST electrical problems

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  • Sprint ST electrical problems

    Heyah folks - I'm a n00b here, so my apologies in advance for any mistakes or etiquette fuckups I might make in this post.

    I'm hoping I can get some advice from the PSB folks on what to do about a running electrical problem I'm having on my Triumph Strint 955i. It's a '99 model with around 70K on the clock - bought second hand 5 months ago from JCS.

    (I'm a mechanical incompetent of the worst order, so any advice would be appreciated, but please keep it simple...)

    I've had an intermittent electrical fault on it - battery is dead when I jump on the bike to ride into work. Not sure if it's a related problem, but it also stalls occasionally as I coast to a stop at traffic lights - does it in neutral as I'm stopping.

    I initially thought it was a bung battery, so I replaced that - didn't fix it (load test says the new battery is fine).

    We've had the mulitmeter over the battery while the engine is running and it's running at a steady 13.5 volts - drops a little on start up, and a little when the lights go on, but well within the normal range.

    I've had it in at both JCS and Motorcycle Electrics, and neither of them could find the problem - ME tool the alternator apart and found some minor corrosion, said it might be that, but the bike was dead again the morning after I rode it home.

    From what I can gather it only seems to be a problem when I've actually been riding it - JCS and ME said they ran the engine and measured the input to the battery and there's no problem, but I don't think they took it out on the road (ME said there wouldn't be a difference, which I find hard to believe).

    ME said there doesn't seem to be any special power drain from the lights and shit when it's running, other.

    I thought it might be a heating issue - ran the multimeter over the terminals after a 20 minute ride the other week and it was reading about 12.5-12.8 volts.

    It was initially happening every week to a week and half, but it's now pretty much dying every time I ride it.

    I'm as frustrated as hell - don't mind spending money to fix the problem, but I can't find anyone who'll do the work to tell me what the fuck it is...

    Any thoughts, advice, places I can take it to?

  • #2
    what you need to do is see if there is any power drain while the bike is off, sounds like the bike is charging the battery at 13.5 V while running, and yes it should make any difference if you are riding it or idling in the shop. My guess would be to check the regulator/rectifyer, in the workshop manual it should show how to test it.

    There are two questions in life.
    1:Which way do I go
    2:Whats the lap record.


    • #3
      Originally posted by Red Rider View Post
      My guess would be to check the regulator/rectifyer, in the workshop manual it should show how to test it.

      There's no separate reg/rec in that model, that was the one where Triumph moved to an integrated alternator. ME said they went over that pretty thoroughly, and it was fine, apart from some minor corrosion.

      Multimeter over the battery terminal with no engine on runs at a steady voltage - 13 or so, and I've never seen that vary.

      I'm starting to think there's a plug loose somewhere that just pulls loose when I'm riding and drops the power, or leaks to earth, but I'd like to be sure before I pull the entire thing apart and start looking at them one by one.


      • #4
        PM'd you crankynick


        • #5
          Something similar happened to me on my '02 Sprint ST following a minor accident repair.

          After an alternator rewind and all sorts of other diagnostic stuff with Motorcycle electrics, they eventually found that one of the connectors into the alternator plug was damaged and the vibration would break the contact whilst I was riding, hence it would pass all the tests whilst stationary, but would drain whilst I was out and about.

          I would be surprised if ME hadn't checked that though, as we all had a pretty frustrating time with mine.

          Best of luck, I feel your pain.
          Adventure before Dementia


          • #6
            Originally posted by evilmart View Post
            PM'd you crankynick
            Thanks dude, got that. Appreciate it.


            • #7
              Update about cranky nicks bike (I helped him replace the alternator and some other general troubleshooting)

              Replaced the alternator on the weekend. Same problem is there, talk about frustrating.

              Here's a list of everything that we have checked.

              Checked for current drain on the bike with everything connected, draw still there.

              Pulled the fuses one by one and not until we got to the main fuse (40amp) did we manage to remove the current drain.

              The only things coming off the main fuse is the starter solenoid and the alternator.

              When the positive output is disconnected from the alternator the current drain disappears. This says that the alternator is the source of the problem. Unfortunately, the current drain is identical with the new alternator in there (it's second hand, but bought from a reputable mechanic in Melbourne).

              I can't see any pinching of wires etc, but even if there was, the current drain would still be there even with the alternator disconnected. I have earthed the old alternator to the bike and checked for current draw across the old alternator and the amount is still the same.

              When I measure for resistance between the body of the alternator and the positive terminal that comes out of it I get a reading of approximately 35k ohms. I am not sure that should be there, I would have thought that the positive and the earth would be completely isolated and I shouldn't have any sort of resistance between the two, it should give and infinite reading? This happens on both of the alternators.

              It's very strange that the new alternator is giving the exact same readings as the old alternator. It leads me to believe that the problem might not be the alternator but something else.

              I just can't get my head around the fact that there is some level of connection between the positive and earth, it just doesn't ring true for me and says to me that there is a problem with one of the diodes within the reg/rect side of the alternator.

              Can anyone shed some light on whether this resistance should be there and whether we are barking up the completely wrong tree? The new alternator was not cheap so picking up another to test isn't really an option. Or alternatively does someone else have a 99 sprint st that I could quickly whack a multimeter across to test some values?




              • #8

                Multimeter will read resistance with leads one way and different with the red/black leads swapped
                The alternator contains the reg/ rec, the second hand hand one has the same problem, a leaky diode in the reg /rec (there are 6) by the sound of things.
                Easist and cheapest solution is run a relay, that closes when the ignition is on, so the alterantor is isolated when the ignition is off, or return the alternator and get a new one.
                What I do for a crust and


                • #9
                  Have you tried disconnecting the starter soleniod from the main fuse?, at this point you can only be wrong. and I'd try similar with the alternator.
                  Harvey community radio has a motorcycling show listen over the web here ,Facebook here yes I am the goose that hosts it.


                  • #10
                    Yeah, have swapped the leads around and get the same resistance both ways. The current draw can only be measure one way with my cheapo multimeter.

                    I will try isolating the starter solenoid and see if that gets me anywhere.

                    Yeah, had already considered switching the main alternator feed with a relay from an ignition 12v somewhere, not hard to do.

                    My main worry with that is that the alternator problem is going to get worse with time and do damage to some other components, though realistically the worst it can do is fry the reg/rec and then the battery.

                    Thanks for the input guys.


                    • #11
                      Stupid question but how much current draw are we talking and how are you measuring it with your cheap arse meter?
                      Harvey community radio has a motorcycling show listen over the web here ,Facebook here yes I am the goose that hosts it.


                      • #12
                        My meter can be put in series to the circuit and measure the current that is flowing in amps. It's measuring about 350 milliamps, and this has been known to spike to 480 after a longish ride. I was guessing that the diodes were failing more the hotter they got.


                        • #13
                          Righto a fair and reasnoable assumption just some people have some funny idea's about current. Actually I remeber reading this in Two Wheels bike doc section where they were having drama's with a 860 GTS. To fault find they took the alt cover off and heated it with a heat gun to operating temp, turned out to be a rotor breaking down with heat maybe try heating it up and see if the resitance betwwen postive and earth changes. Just out of curiosity did you replace the rotor when you replaced the alternator, what relationship is the rotor to the rest of the system IE is it a simply a permanet magnet or doest it have a excitation current that feed to it via slip rings or similar arrangment. Although if a Diode is going you would expect to have low charging voltage on top of the other issues. Although check the wiring again 350miil amp is [email protected]#$all on the higher current ciruits and its possible where its rubbed through is very minor, the circuits contain enough current that a dead short to earth would simply eat the 40 amp fuse.

                          Actually just re read the intial problem, its not charging ethier might be worth testing at 5000 rpm you should see around 14.5 volts at the battery 12.8-13 is a battery in good condition but not been charged, a lot of bikes don't charge at idle this is changing but you really need a workshop manual to know one way or the other.
                          Harvey community radio has a motorcycling show listen over the web here ,Facebook here yes I am the goose that hosts it.


                          • #14
                            Do you have both headlights on at the same time? (Triumph Sprint ST Information)

                            or this prob

                            Triumph Sprint ST Information
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