Why doesn't my alternator work? :(

Discussion in 'Mech Tech' started by Zed, Dec 23, 2015.

  1. Zed

    Zed Gradually getting grumpier

    Type-4 engine
    Nada - light stays on and I was using the blue wire to trigger the fuel pump. :mad:
    I replaced all the wiring into the back of it before I fitted it. I chose it from 3 possibles because it "looked" the best.
    Could it be the regulator? That was on the bus when I got it, no idea if it's good.
    Have MOT booked in an hour, I'll get that far but...
     
  2. yep could be the regulator, is the light wired correctly in the dash? is it a normal bulb? have you checked the o/p voltage from the alternator?
     
    Last edited: Dec 23, 2015
  3. sANDYbAY

    sANDYbAY On benefits-won't sponsor!

    No idea about your alternator, sorry, but good luck with the MOT. :thumbsup:
     
    theBusmonkey likes this.
  4. MorkC68

    MorkC68 Administrator

    Have you checked the voltage coming off the alternator to the reg as a first port of call?
     
  5. Fish

    Fish Administrator

    Sounds like the regulator to me. The telltail light is on when its a closed circuit if you then use that back feed (0+-) cancel from the regulator to then power another device it will mess the regulator up and when you reconect the telltails earth to the regulators blue wire it will stay earthed (fried).
     
  6. Zed

    Zed Gradually getting grumpier

    Not quite sure what you mean. I'm taking feeds off the blue wire to switch relays - one for the split charger and one for the fuel pump, nothing is running directly from it.
    Is it supposed to click because it does at the same time as the coil gets power eg if I connect direct from battery to coil it clicks?
     
    Fish likes this.
  7. Zed

    Zed Gradually getting grumpier

    No, it ran until the carbs were empty then stopped. I've just wired the pump alternator relay signal to the coil instead so I'll check it when I've scoffed this cheesey bean Pasty. :)
     
    Datsolow and MorkC68 like this.
  8. Zed

    Zed Gradually getting grumpier

    What is this?
     
  9. MorkC68

    MorkC68 Administrator

    I think ours threw a bit of a wobble when we first cranked the motor into action; the plug wasn't pushed home enough!
     
  10. Zed

    Zed Gradually getting grumpier

    Tried that. :)
     
  11. Fish

    Fish Administrator

    the light in the clock is the telltail bulb. its powered from the fuse box and goes out when the earth becomes + from the regulator. simple side of the same powered system is the oil light...
     
    bluething likes this.
  12. Fish

    Fish Administrator

    remove the split charge relay so you just have the + from the bulb attached to the regulators blue wire. if the bulb stays on then... then its the regulator. if it goes off then its either the relay or the split charger causing a voltage leak!
     
    Lasty, zed and bluething like this.
  13. I'm liking this 'Fish' chappy, he explains stuff in simple terms for us numbnuts.
    We should encourage him to hang around I think. ;)
     
    art b, brothernumberone and Lasty like this.
  14. have you checked the big wire from the starter to the alt is still attached? :oops:
     
    zed and Fish like this.
  15. While you're fiddling, be careful not to short the alt light output to ground while the engine's running. You'll likely pop the small auxiliary diodes inside the alternator.
     
    zed and Fish like this.
  16. Fish

    Fish Administrator

    They're like cats lives. There are normally 9 lives in the diode array and You'll never know how many you have left till the last expires!
     
  17. Fish

    Fish Administrator

    Any bets on a pass for the MOT and if he got back home yet?.. Its over the hour and MOT time... Search party maybe?
     
  18. I found out this out when wiring in ahandbrake switch using a late wiring diagram on a crossover bus.o how i laughed!
     
    snotty likes this.
  19. Fail on windscreen wash insufficient to clear screen:lol:
     
    AndyC likes this.
  20. Bhubesi

    Bhubesi Supporter



    If you have a Diode gone in the regulator, you can hear it in the speakers, a whining sound that rises and falls with the revs.
    Tony
     
    Fish and zed like this.

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