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alternator confusion


series3100
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I'v searched about alternator wiring and now know in order for an alternator to work it first has to be energised (i think). So how do i wire it up properly? currently the big terminal (can't remember the name, b+?) goes directly to the starter solenoid. The w terminal goes directly to the charge light and to make a long story short it doesn't work. I even swapped the alternator for a spare then realised it was more likely to be my wiring.

Thanks in advance :)

Brian

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I'm pretty sure i put the big wire to the same side of the solenoid as the main battery +ve cable goes to.

The charge light doesn't seem to be up to much any more, used to come to life. Its a 200tdi btw.

Cheers, Brian

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I'v searched about alternator wiring and now know in order for an alternator to work it first has to be energised (i think). So how do i wire it up properly? currently the big terminal (can't remember the name, b+?) goes directly to the starter solenoid. The w terminal goes directly to the charge light and to make a long story short it doesn't work. I even swapped the alternator for a spare then realised it was more likely to be my wiring.

Thanks in advance :)

Brian

Right, the ''w'' terminal is for a rev counter signal, normally used only on Diesel engine applications. Energisation for the alternator comes from the charge light circuit and it's respective connection (which will be the other small terminal normally alonside the main terminal(s)

Julian.

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I lied! the little wire goes to D+ (just looked and i think that's what it says) I think this is my issue as that wire goes directly to the charge light, if its this circuit that does the energising then it'd have to magic up some energy :lol: . How do i go about energising this circuit?

Oddly I'm sure the charge light did work a while back...

Thanks a lot, I'm a bit of a hater of electrickery!

Brian

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One side of the charge light is connected to ignition live, I thought the other to the "w" (for "warning light") connection on the alternator? The bulb has to be working and of the right type for the alternator to work properly.

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I lied! the little wire goes to D+ (just looked and i think that's what it says) I think this is my issue as that wire goes directly to the charge light, if its this circuit that does the energising then it'd have to magic up some energy :lol: . How do i go about energising this circuit?

Oddly I'm sure the charge light did work a while back...

Thanks a lot, I'm a bit of a hater of electrickery!

Brian

Yes the D+ wire is for the charge light. If you ground this wire the charge light should illumiate, (obviously with ignition on) this is your first port of call, get this (charge light circuit) confirmed as working before doing anything else.

(when the alternator is charging it supplies 12volts to the D+ terminal which matches the 12 volts at the bulb supply and so it no longer illuminates)

Julian.

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Yes the D+ wire is for the charge light. If you ground this wire the charge light should illumiate, (obviously with ignition on) this is your first port of call, get this (charge light circuit) confirmed as working before doing anything else.

(when the alternator is charging it supplies 12volts to the D+ terminal which matches the 12 volts at the bulb supply and so it no longer illuminates)

Julian.

Ah that is my solution by the sound of things. Here is what i'v done: I more or less assumed i just had to run a wire strait to the charge light then from the other side of the light to ground. So if i understand you correctly there should be power (an ignition live) to the charge light which is also the power that activates the alternator. Sounds simple enough... :P

I'll have a poke about and get back to you.

Thanks, Brian

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Ah that is my solution by the sound of things. Here is what i'v done: I more or less assumed i just had to run a wire strait to the charge light then from the other side of the light to ground. So if i understand you correctly there should be power (an ignition live) to the charge light which is also the power that activates the alternator. Sounds simple enough... :P

I'll have a poke about and get back to you.

Thanks, Brian

Yes, you understand me correctly, that's what you must do.

Here's another post on the difflock forum

The ignition switch is basically sending a signal through the charging light bulb and then down to the alternator through the field windings to ground. Hence when at rest the light comes on when the ign is switched on. So you will have to find that circuit and connect it to F

Essentially when you start the engine up and the alternator comes on charge it sends out a flow, NOT ONLY down the B+ve fat wire BUT ALSO out through the F terminal. As the flow of electrons goes up the thin wire it stops the downward flow to the ground--so light goes out! Charging is taking place.

Now connect the battery and check your work--If it is correcty installed you won't let the smoke out!

Just to clear up some possible confusion by another post on the matter, the 'W' terminal is for a rev counter drive and takes no part in the charging circuit.

http://homepage.ntlworld.com/william.whittaker1/alt_strip_repair.htm

Julian.

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Yes, you understand me correctly, that's what you must do.

Here's another post on the difflock forum

The ignition switch is basically sending a signal through the charging light bulb and then down to the alternator through the field windings to ground. Hence when at rest the light comes on when the ign is switched on. So you will have to find that circuit and connect it to F

Essentially when you start the engine up and the alternator comes on charge it sends out a flow, NOT ONLY down the B+ve fat wire BUT ALSO out through the F terminal. As the flow of electrons goes up the thin wire it stops the downward flow to the ground--so light goes out! Charging is taking place.

Now connect the battery and check your work--If it is correcty installed you won't let the smoke out!

Just to clear up some possible confusion by another post on the matter, the 'W' terminal is for a rev counter drive and takes no part in the charging circuit.

http://homepage.ntlworld.com/william.whittaker1/alt_strip_repair.htm

Julian.

It works, kind of anyway.

I ran an ignition live onto what was the earth side of the bulb and it now lights up when the ignition is turned on, when the engine is started and reved though it doesn't go out, it does vary in brightness slightly though. The alternator is defianatly charging now, i was getting a touch over 14.5v then when the engine was shut down it goes to more like 13v so I'm getting there! I would of fiddled around a bit more but it was raining very wet rain...

Cheers, Brian

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It works, kind of anyway.

I ran an ignition live onto what was the earth side of the bulb and it now lights up when the ignition is turned on, when the engine is started and reved though it doesn't go out, it does vary in brightness slightly though. The alternator is defianatly charging now, i was getting a touch over 14.5v then when the engine was shut down it goes to more like 13v so I'm getting there! I would of fiddled around a bit more but it was raining very wet rain...

Cheers, Brian

14.5 Volts is a good charging voltage for old style alternators.

I'm not sure how you have this charge warning light rigged, but you must use a bulb of around 2 watts - LED style bulbs or bulbs with lesser wattage won't do the job properly.

Anyway, if you have a bulb of suitable wattage, have the wiring correct, have the belt tight and the bulb does not extinguish then it normally points to an internal alternator fault.

Julian.

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14.5 Volts is a good charging voltage for old style alternators.

I'm not sure how you have this charge warning light rigged, but you must use a bulb of around 2 watts - LED style bulbs or bulbs with lesser wattage won't do the job properly.

Anyway, if you have a bulb of suitable wattage, have the wiring correct, have the belt tight and the bulb does not extinguish then it normally points to an internal alternator fault.

Julian.

The alternator is actually a late 300tdi one that i had lying around. I swapped it on a while back because the alternator fitted wasn't working (I thought!) - I'll check the bulb and if that's not suspect will see what happens if i swap alternators again.

Cheers, Brian

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