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D14 Generator / Alternator Testing When No Charge in I
Mick W
Chester/ North Wales Flintshire Border
Forum Posts: 875
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June 13, 2015
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August 30, 2019 - 9:54 pm
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Mikef asked if this could be placed in FAQ. 

Spacedmarine wrote

Just taken mine out for a Sunday morning ride and it started to sound like the thing was running out of petrol anyway it finally conked out in the middle of nowhere and wouldn't restart.The battery was flat as a pancake.Anyway started on emergency eventually then conked again when switched back to I.For some unknown reason I switched the headlight on and it ran ok on I.I guess this explains it.When i made it home checked the voltage at the battery and it was all over the place reading as high as 8.5 volts.Im guessing the rectifier is U.S.?

Hi SpacedMarine.
        It seems to me that your fault could be with the generator. It is very common for the yellow wire from the generator to break under the wire clip on the stator. This will cause a no charge condition in the I position and reduced charge when the headlamp is on.
The battery voltage reading with a cheaper type digital voltmeter can be unreliable with the engine running as the spiky voltages produced by the generator can "confuse" it. The readings will be erratic.

A resistance check on the wires from the generator would be a good idea. You may find that you have an open circuit between the green and yellow wires. The fix is normally quite easy, just remove the insulation from the wires under the clip, re-solder the break and re-insulate.

Good luck.


All pictures from member SpacedMarine DEAD23B3-EB74-49AD-91E8-785B6768F500.jpeg

It appears the yellow wire from the alternator has broken away.No worries a little solder and heat shrink seems to have fixed it.




I now have continuity between green and yellow wires

Top Gear User
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September 2, 2019 - 3:38 pm
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Hi. That happened on my B175 and it was the yellow wire broken at the alternator. A Telecom engineer friend soldered it up for me and all was - and still is - well.

two B175s and a CB360

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