Alternator & Ammeter
Posted by John Payne On 2016/6/8 2:35:38
G'day All, I realise the topic of alternator conversions has been done before but I find it pretty difficult to locate the files and add to them. In any event, my concern is not so much the alternator but the ammeter and how this invisible substance called electricity works.
But first, I did a fair bit of research on the internet on how to wire-up a three wire alternator and have now done so on my '56 Patrician. The generator was removed and the three wires attached to it taped off and not used again. The existing generator bracket was retained, although the bolt holes had to be elongated, and the tensioning bracket was retained as well.
The alternator is a Bosch 85 amp universal type and, from what I learned on the net and the Bosch wiring instructions, the main power cable should be 6 B & S, which I understand is the same as 6 AWG. Also, to protect the rest of the car's electrics in the event of alternator failure, the advice is to make sure this cable is fused, and I've done that with a 100 amp "megafuse". This cable joins with the battery cable at the starter solenoid. The other two wires are marked "L" for lamp (idiot light) and "S" for sensing. The "S" wire is connected to the hot wire on the horn relay and, as I don't have an idiot light, the "L" wire was connected to the power seat relay where the Chevy wiper motor draws its power. I put a resister in the "L" wire so that the alternator would be excited sufficiently to commence charging.
When tested, the battery was showing 13.0 volts and soon as the car was started the charge was measured at 14.4 volts, which told me the alternator is charging. Bosch advise that the internal regulator is set to charge at 14.2 volts, give or take depending upon temperature. After a short drive the charge rate was down to 14.15 volts so it appears as if the alternator is doing its job. I've attached some photo's so you can get an idea of how it looks.
Now to my concern. Switching the headlights on before starting prompted the ammeter (Gen) needle to swing to the discharge side about a third of the way. Checking after starting, the needle went to about the same position. This suggests to me that there is a wiring issue affecting the ammeter and I've got no idea of how to fix it. I've had a good look at the wiring diagram and can see how the red wire from the generator regulator goes to the ammeter, but of course it now has no current being fed into it. I would prefer to retain the ammeter but if it must be disconnected then so be it. Has any body got any suggestions of the best way to fix it? Cheers, John
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But first, I did a fair bit of research on the internet on how to wire-up a three wire alternator and have now done so on my '56 Patrician. The generator was removed and the three wires attached to it taped off and not used again. The existing generator bracket was retained, although the bolt holes had to be elongated, and the tensioning bracket was retained as well.
The alternator is a Bosch 85 amp universal type and, from what I learned on the net and the Bosch wiring instructions, the main power cable should be 6 B & S, which I understand is the same as 6 AWG. Also, to protect the rest of the car's electrics in the event of alternator failure, the advice is to make sure this cable is fused, and I've done that with a 100 amp "megafuse". This cable joins with the battery cable at the starter solenoid. The other two wires are marked "L" for lamp (idiot light) and "S" for sensing. The "S" wire is connected to the hot wire on the horn relay and, as I don't have an idiot light, the "L" wire was connected to the power seat relay where the Chevy wiper motor draws its power. I put a resister in the "L" wire so that the alternator would be excited sufficiently to commence charging.
When tested, the battery was showing 13.0 volts and soon as the car was started the charge was measured at 14.4 volts, which told me the alternator is charging. Bosch advise that the internal regulator is set to charge at 14.2 volts, give or take depending upon temperature. After a short drive the charge rate was down to 14.15 volts so it appears as if the alternator is doing its job. I've attached some photo's so you can get an idea of how it looks.
Now to my concern. Switching the headlights on before starting prompted the ammeter (Gen) needle to swing to the discharge side about a third of the way. Checking after starting, the needle went to about the same position. This suggests to me that there is a wiring issue affecting the ammeter and I've got no idea of how to fix it. I've had a good look at the wiring diagram and can see how the red wire from the generator regulator goes to the ammeter, but of course it now has no current being fed into it. I would prefer to retain the ammeter but if it must be disconnected then so be it. Has any body got any suggestions of the best way to fix it? Cheers, John
Attach file:
(299.99 KB)
(227.51 KB)
(349.68 KB)
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