Rectifier/regulator, magneto or battery?

Discussion in 'Mechanics Garage' started by Damien, Jun 22, 2012.

  1. Damien

    Damien New Member

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    Hi all, I have a 1989 Honda VFR 400 NC24 and I am having a problem with my battery. The battery just ran dead all of the sudden and I am just wondering what it could be. I'm thinking rectifier/regulator since my bike runs with the battery if I run-start it but the battery doesn't charge. The bike dies as soon as I disconnect the battery ( Should it do that?) It would really be a great help if someone could just point me in the right direction. Thanks.
     
  2. fieldsanitation

    fieldsanitation New Member

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    you got a meter? have you checked all the fuses?
     
  3. Damien

    Damien New Member

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    I don't have a meter and I have no idea how one works, but some of my friends do, luckily. I checked all the fuses, yes, if you mean the ones at the ignition. Those are the only fuses I know of and there are 9 of them. The thing is, when I charge the battery it charges fine but it doesn't charge in the bike at all.
     
  4. pjvtec

    pjvtec New Member

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    Yeah...ya might not wanna disconnect that battery while it's running. You gotta do your tests.
     
  5. DeannaLee

    DeannaLee New Member

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    Going through some of the same issues right now myself. A tester and a good shop manual goes along way. You should be putting out 13.5v-14v at 5000 rpm, make sure your batt is charged before testing, if that does not test right then check the resistance and continuity of the stator. Hate admitting it but I had to take mine down to a dealer to get it diagnosed. Gonna end up replacing both stator and rr.
     
  6. kennybobby

    kennybobby New Member

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    There is a big 30 amp fuse on the starter relay that would prevent the battery from charging if it were blown or missing--did you happen to check that fuse?

    Don't disconnect a battery while the engine is running--never a good idea to do this.

    Get your friends to measure the battery voltage when the engine is off and let us know what it is. If your battery is weak it could have caused the above-mentioned fuse to blow. The battery may be okay since you can charge it off the bike, but lets hear the test results first.

    If the 30amp fuse is okay, then check the connector on the RR looking for signs of heat distortion, melting, or burn marks in the plastic, burnt wires or connector lugs, etc. especially the three yellow wires and the red wire coming out of the RR.

    There is no magneto per se, but there is a 3-phase AC alternator. The three yellow wires at the RR connector are the stator wires for the alternator. Get your friends to measure the resistance between those 3 wires taken 2 at a time--all three readings should be about the same value. Then check if there is any resistance between any yellow wire and the engine case--normally there should be no continuity as it is an open circuit with "infinite" resistance.

    There may be some other tests but this is a good start until we know more.
     
  7. Damien

    Damien New Member

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    Thanks dude I'll see what I can get sorted out. I didn't know about the 30amp fuse and I'll start by checking that.
     
  8. Damien

    Damien New Member

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    I saw a fuse that's almost on the solenoid. It's a 20amp fuse. That's all I could find. My friend says he thinks it's the R/R since there was a pirate one in(It was in when I bought the bike). So yea, he said he will get a meter somewhere and test all those things for me but as it seems so far I'll have to buy a new R/R. Thanks for everything so far guys.
     
  9. pjvtec

    pjvtec New Member

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    I believe that fuse on the solenoid is the main fuse. The bike would not power up if that was blown.
     
  10. kennybobby

    kennybobby New Member

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    pj is right--if the main fuse is blown there would be no power anywhere, not just the path for charging the battery.

    It does seem that either the RR or the alternator is not working--most likely candidate is the RR.
     
  11. Damien

    Damien New Member

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    Thanks again guys. I'm just wondering, would the bike ride at all if the alternator was broken? I heard that it wouldn't.
     
  12. kennybobby

    kennybobby New Member

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    It could start and run with a defective alternator, but only until the battery was depleted, then you would be stuck on the side of the road...That's an old trick we used to do on race bikes to reduce weight and gain a couple of horsepower--pull the alternator and use a freshly charged battery.
     
  13. Mohawk

    Mohawk New Member

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    And you stop your petrol engined vehicles HOW ? That's what an ignition switch does, it kills the electrical power to the engine. There is nothing wrong with disconnecting a battery on an petrol engined vehicle, its the same as turning the ignition off. It's not good to do it by unscrewing the battery terminal, better with a quick clamp as the disconnect is cleaner, but other than that it should not cause any harm.
     
  14. Mohawk

    Mohawk New Member

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    Get a Volt meter, charge the battery, let it rest for a couple of hours then check the voltage should be 12.7V or higher for a fully charged battery in good condition.
    Now disconnect the rectifier/regulator from the alternator, normally 3 yellow wires on a Honda, then set the meter to OHM's (resistance) then measure the resistance between each of the wires on the alternator side plug. It should be less than 1 ohm & then measure each wire to earth, as in the frame of the bike, it should not read. If that checks out, then the alternator is fine.

    Attach the meter to the battery terminals set for Volts note the reading & start the engine, the voltage should dip when the starter runs, then return to its previous reading, so for example if it says 12.6v then dips to 11v when the starter is running, it should then return to 12.5v ish. If the regulator/rectifier is doing its job (which we suspect its not), then with the engine running at idle the voltage should show 13v+ & when revved to 5000 rpm it should show 14v+ if you don't get this then the reg/rectifier is knackered, get a new one.
     
  15. kennybobby

    kennybobby New Member

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    An Education can be Expensive...

    While it is true that we turn off our motorsickles by cutting the power flow thru the kill switch, hopefully y'all realize that is not the same as lifting a terminal off the battery while it's running.

    Ever since 1984 i've had a small electronics repair business specializing in Bosch Motronics, which is the engine control unit (fuel injection and ignition) used in many european car$ and bike$. After looking at hundreds of these units and talking to the owners i found certain defects and common failure patterns. One pattern was quite remarkable in that certain copper traces were vaporized right off the printed circuit board! Guess what the guys were doing with their battery terminals when they smoked those expensive units?

    Current don't talk, current just flow. If current don't have a path back, current make one.

    But who knows--maybe those Japanese engine control units in the fuel injected bikes are somehow immune to the interruption of current flowing in inductive circuits while running, but i'd be willing to bet real money they're not...any takers?
     
  16. Damien

    Damien New Member

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    Thanks a lot guys. It seems it was my stator coil. Took my bike to a mechanic to get her fixed and after he replaced the stator coil, she ran like a dream again.
     
  17. squirrelman

    squirrelman Member

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    lot of us oldtimers grew up with cars, and back then it was a good test of the generaTOR to disconnect THE BATTERY while running, but NOT ON BIKES now !!!!
     
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