The Eternal Alternator Choice Topic

[JPerkins]

J, Voltage regulators use off/on switching to control output voltage via the rotor coil current. Some alternators, most notably Delco use a capacitor across the VR inside the alternator case to quiet it down.

Well, I'll keep looking for a voltage regulator, maybe even straight from denso.
If anyone has a line on one let me know.

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[Jeff J]

I don't know anything about Denso other than I will not install one. I had one spin the nut and pulley off. Normal direction of rotation on the one that failed loosens the nut and there was no provision for a key on the shaft or pulley... just a set screw to hold the pulley when the nut came loose. My guess is the pulley nut was not properly torqued but, without a keyed shaft to keep the pulley from turning against the nut, I certainly wasn't going to install another one. There was no model number or ID plate on this one maybe other models have a keyed shaft.

[Jeff J]

I don't know anything about Denso other than I will not install one. I had one spin the nut and pulley off. Normal direction of rotation on the one that failed loosens the nut and there was no provision for a key on the shaft or pulley... just a set screw to hold the pulley when the nut came loose. My guess is the pulley nut was not properly torqued but, without a keyed shaft to keep the pulley from turning against the nut, I certainly wasn't going to install another one. There was no model number or ID plate on this one maybe other models have a keyed shaft.

I made that post working off the assumption the problem alternator is a Denso because the auto parts store could not identify it and someone told me that is what it is (from a tractor). However, it does not look like any of the Denso alternators pictured in this thread. There was no documentation for the installation.

[JPerkins]

Looks like a motorcraft alternator to me. Also every alternator I know of does not have a keyway and works off the clamping force of the nut. If it spun off then it was likely not torqued properly.

[Jeff J]

I thought all alternators use a woodruff key. I don't have experience with non-aviation components and haven't had to remove many pulleys over the years since they come installed. I chose Plane-Power because their drawing shows a slot for one in the pulley. I didn't disassemble it to confirm it though. The Hartzell and Kelly alternators do for sure because checking the woodruff key for damage is a step in replacing the fan.

I don't have one to look at here but I was thinking Motorcraft had a fan under the pulley. The rear connections on this thing are different too. That is what was throwing off the guy at the parts store.

[Rick-CAS]

I had one like that on my RV-3. It's a Mitsubishi alternator. I think it was made by Nippendenso before they became Denso. Mine had a Mitsubishi logo cast on the back. It beat the rear bearing out of it but it never failed just was making noise during the condition inspection.

[Jeff J]

Thanks Rick, I had been wondering about that thing. No markings on it other than the standard wire connection letters and a sticker from the shop that did the last rebuild. It didn't truly fail, I just found the pulley laying on top of the carb heat box after flight and it had ruined the threads on the shaft before it came off. Judging from the shop sticker on the side it likely had less than 20 hours since rebuild but I don't know if the previous owner or the shop installed the pulley.

[Jeff J]

I thought I would seek confirmation from Plane-Power on the drawing that I thought showed a keyed pulley so I sent them an email. I was disappointed to learn none of their belt driven alternators use a keyed shaft.

[Homer Landreth]

Well, I'll keep looking for a voltage regulator, maybe even straight from denso.
If anyone has a line on one let me know.

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Given another opportunity, I will go with a Denso Alternator, Single wire, Internally excited, self Regulated, and trash the separate regulator. I don't see (but understand there will be differing opinions by others) where there is value or safety added by using a separate Voltage regulator on an alternator any more.

[Jeff J]

I agree, internally regulated is good. I also like over-voltage protection built in. Installations are simpler and I prefer the KISS approach. Having said that, my tractor had a single wire alternator when I bought it that I replaced for one using a separate field circuit because it was acting more like a generator than an alternator. I had to rev the engine up to get it to start producing power and once activated, it produced very little power at idle which was problematic doing light work around the yard especially if I was using the lights. It was fine if I was using the brush hog or some other operation where I had to keep the rpm up. It should be noted technology changes and not all single wire set ups have that failing but I thought it was a potential pitfall worth mentioning.