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Thread: Mk2 Pinto Alternator Wiring

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    Mk2 Pinto Alternator Wiring

    Hey,

    I know this has been asked a lot from looking in the search but I am having issues with the alternator. I have a standard pinto engine with a standard ford alternator it seems. When starting the engine the voltage didn't change and the charge light on the dash never came on. As I didn't know the history of the alternator I got a new one bit it does the same thing.

    I tried connecting B+ (didn't have a switched live nearby) to W no change again.

    I tried bridging the B+ to the blue wire that goes to the dash light and that makes the dash light come on and the alternator works, get 14+ volts. The charge light stays on all the time.

    Connecting the terminals in yellow worked and connecting the ones in red did not.

    Click image for larger version Name:	alternator.JPG Views:	124 Size:	135.6 KB ID:	85049

    Does anyone know what I am doing wrong?
    Last edited by lewisco; 18-01-2020 at 16:04.

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    Re: Mk2 Pinto Alternator Wiring

    Why on earth did you connect B+ to W etc?
    From the photo the std wiringplug is dodgy to say the least ...
    You only need the 3-pin plug (2 red wires and the blue one); make sure these wires and their connectors are in good order.
    Remove anything attached to the W- and B+ terminal.
    If it still isn't working connect an extra earth wire from alternator housing to engine block.

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    Re: Mk2 Pinto Alternator Wiring

    I thought I read that somewhere. Connect a switch ignition to the W wire.

    I have added a ground strap from the alternator body to the chassis too.

    The blue wire on the plug is a little dodgy. I’ll try re-wiring that connection. Thanks.

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    Re: Mk2 Pinto Alternator Wiring

    Ran a new wire from the blue wire on the alternator plug direct to the charge bulb on the dash and still no luck.

    The dash isn’t original and the charge bulb is just one of the small round ones from Halfords.

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    Re: Mk2 Pinto Alternator Wiring

    is there power to the charge bulb?

    how the system works is the dash supplies a + feed to the charge bulb the other side of the charge bulb is earthed out by the alternator.

    so to prove whether the dash is at fault, connect a small bulb to the battery + and the other side of the bulb to the alternator "blue" wire, the bulb should light, start the engine and the bulb should go out.


    the alternator should still work even with the charge bulb not working, you just have to rev the engine to excite the alternator, easy to check if that happens with a multimeter, just measure the voltage across the battery terminals, engine off you should have around 12.5, engine running should be over 13 once you have reved it up

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    Re: Mk2 Pinto Alternator Wiring

    Normal connections are - Bat/B+ .... Direct to Battery or Battery side of Starter Solenoid, D .... to one side of warning light, the other should be connected to ign sw. live and W....... can be connected to Ign sw. live or be left disconnected.
    This last connection is strange in that connection will allow charging immediately as field coils will be energised but if not connected, the field coils will eventually form a field based on rpm and turning - usually a good blip of throttle does it - its all down to physics (apparently! LOL)

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    Re: Mk2 Pinto Alternator Wiring

    Ah, my charge bulb is wired incorrectly:

    alternator blue wire -> bulb -> ground

    where it should be

    alternator blue wire -> bulb -> ignition live

    I’ll give that a go! Thanks everyone.

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    Re: Mk2 Pinto Alternator Wiring

    Well adding a switched live to the other side of the charge bulb did the trick! Makes perfect sense when thinking about it and bridging the alternator charge light wire to B+.

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    Re: Mk2 Pinto Alternator Wiring

    It works that way because when at rest the warning bulb earths itself via the alternator body to ground. When running there is power into that same line and the two cancel each other out. Its also why, if the alternator power is dropping off, the light will glow dimly - there is more battery voltage on one side against lower alt. voltage / increased earthing!
    This is also why you can't use LED warning lights for alternators - they only pass volts one way!

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    Re: Mk2 Pinto Alternator Wiring

    Does the blue wire for the exciter circuit come into the fuse board or is it a direct wire through the loom to the dash? I had a very dull – warning light so I added an extra earth to the alternator as I have the rubber RS 2000 alternator bracket I now have a very strong charge light but somehow this will now not turn off and my alternator doesn’t seem to be charging��

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    Re: Mk2 Pinto Alternator Wiring

    Quote Originally Posted by faithle55 View Post
    Does the blue wire for the exciter circuit come into the fuse board or is it a direct wire through the loom to the dash? I had a very dull – warning light so I added an extra earth to the alternator as I have the rubber RS 2000 alternator bracket I now have a very strong charge light but somehow this will now not turn off and my alternator doesn’t seem to be charging��
    wire goes straight to dash.

    this will now not turn off and my alternator doesn’t seem to be charging
    makes sense if the alternator doesnt work the light wont go out. most likely the lack of an earth for the alternator fried it

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