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Hi all, while I'm getting the Montreal ready for Canada, we discovered that the green alternator wire that supposed to be plugged into the large resistor over the right fender was disconnected. Everything was working but the alternator only produces 13.2 volts. When we plug the alternator wire to the resistor we get 13.6 volts. The problem lies in the fact that when plugged in and I turn the key off there is a back feed to the alternator and it keeps the engine running and resistor overheats.
Engine shuts off as soon as we unplug the wire from resistor.
I don't know if the resistor was changed by previous owner but I need to fix because battery is not getting a sufficient charge.


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Papajams Montreal wiring drawing shows how the alternator should be connected. I would check the alternator and voltage regulator connections first (to make sure all colors -- but especially the brown and green ones -- are on the correct DF/D+/D- terminals of both the alternator and voltage regulator).

BTW, the excitation resistor is fed from a pink wire that comes from fuse #2, which in turn is fed battery voltage by the ignition switch. From the resistor the green wire should go via the voltage regulator to the alternator.

10564 Montreal no AC R4 (cropped + 700 wide).jpg
 

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Hi. You mention a "large resistor" on the right fender, but on my '71 it is contained in a small box on right side of the cowl. The purpose of it is to supply initial excitation to the alternator field. Once the alternator starts charging, the "D+" terminal becomes active, supplying the the regulator/field circuit, and the resistor then has no function in the charging circuit. If you disconnect the resistor (green wire) without the engine running, there should be no voltage on that wire, in other words the "D+" terminal is zero. If there is, it would indicate shorted diodes in the alternator. The resistor on mine is app. 50 ohms. Hope this is of some help.
 

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Hi. You mention a "large resistor" on the right fender, but on my '71 it is contained in a small box on right side of the cowl. The purpose of it is to supply initial excitation to the alternator field. Once the alternator starts charging, the "D+" terminal becomes active, supplying the the regulator/field circuit, and the resistor then has no function in the charging circuit. If you disconnect the resistor (green wire) without the engine running, there should be no voltage on that wire, in other words the "D+" terminal is zero. If there is, it would indicate shorted diodes in the alternator. The resistor on mine is app. 50 ohms. Hope this is of some help.


Thank you, we will look into that next week and report on outcome


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