JeffJeffers
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| posted on 9/2/12 at 05:36 PM |
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Alternator wiring
Having a few problems with my alternator wiring.
 
alternator
This is the alternator I am using. It has 3 terminals on the back, 2 big and 1 small.
The 2 big terminals go to the battery. The small terminal goes to the battery light on the dash. The other connector on the battery warning light goes
to a switch live.
If I run the engine the battery light stays on and the alternator doesn't have an output.
If I disconnect the small cable from the back of the alternator and test it I get 12 volts when I turn the ignition on. If I plug it back into the
alternator and test it I get less than 2 volts, which I guess is to enough to engage the alternator.
What I think is happening is that the bulb is draining to much voltage. If this is the case how do I fix it?
This is the battery warning light that I am
using.
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MakeEverything
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| posted on 9/2/12 at 05:51 PM |
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Those are more or less the same symptoms I have. Watching with interest, though I haven't tried to fix mine yet, since the engine has been out.
Kindest Regards,
Richard.
...You can make it foolProof, but youll never make it Idiot Proof!...
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rachaeljf
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| posted on 9/2/12 at 06:21 PM |
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What wattage bulb have you got in the warning light? You need a 2W or 3W bulb.
Cheers R
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mark chandler
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| posted on 9/2/12 at 06:42 PM |
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The battery energises the coils in the alternator when stopped, once it starts spinning volts go the other way, on a Jag I had the battery light
remained lit so added a diode on the wire to sort, not sure why but I goggled and that was the solution as the light should really extinquish as 12v
one way is cancelled 12v the other way putting out the light.
Regards Mark
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omega 24 v6
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| posted on 9/2/12 at 06:46 PM |
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Looks like an ACR lucas jobbie.
As said check your bulb is 3 watts
If it looks wrong it probably is wrong.
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Stott
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| posted on 9/2/12 at 06:47 PM |
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You need enough current to flow in the D+ to excite the alt so as stated you need a minimum of a 2W bulb, try taking the spades off the back of the
battery light you are using and connect up a spare lamp holder you have with a 501 sidelight bulb in it or similar.
I run an acewell dash and the led in the warning stack cannot be used to excite the rotor windings so I also run an old oval repeater lamp I had lying
about tucked under the dash out of the way.
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snowy2
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| posted on 9/2/12 at 07:33 PM |
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make sure you use a light bulb and NOT an LED!
the battery light should get its power from the ign. sw. to the bulb then the other terminal should go to the alternator direct.
the alternator charge wires should connect to the Battery live (+ve) terminal EITHER directly or usually via the starter motor live connection on the
solenoid......The HOT side not the COLD side (seen it)
The Alternator MUST be earthed.....via the engine usually but i have seen alternators mounted via isolation blocks.
sometimes you are the pigeon, most of the time the statue.
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JeffJeffers
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| posted on 10/2/12 at 01:43 PM |
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Ok I have fixed my problem.
Like you have all said the warning light bulb needs to be 2w or 3w, which I didn't know. I had a spare waning light that I wasn't using so
I pulled it to pieces. I then soldered a new 2w bulb on. Pluged it all in and away we go.
Now all I need to do is swap the bulb holder into the battery light on my dash.
Thanks everyone for your help as always
 
ALT WARNING LIGHT
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