1969 alternator

[blake5179]

I am working on a 1969 CJ5 with the V6. This is not my Jeep (although I would love to own it). I'm working on it for a neighbor.
I have the Jeep running pretty well now but wasn't getting anything out of the alternator.
Original:


I took it to two different auto parts places and had them check it. Because I don't really trust what just one of them would say... anyway both said it failed and wasn't charging, which is what I was finding with my meter as well so I tried to order a replacement.
Neither one of them could order the 37 amp replacement. Said it wasn't available. So I did some research and found the 37 amp AC Delco part # 334-2105 and the 55 amp AC Delco 334-2209.
I called back to the parts place and asked if they could cross reference anything to the AC delco 2105 number. They said yes and I ordered it. When it shows up though it looks more like the 55 amp version.
Kid says I can take it home and try it and bring it back if it doesn't work. So I did some more research and found this electrical drawing:

Knowing where to hook up the wires I installed the new one.

First thing I did was check voltage output, same procedure as original unit, unplug voltage regulator, unplug clip on wire from #5 on drawing above, make pig tail from Regulator terminal #3 above, start engine, connect pig tail from regulator #3 to #5 with engine running. Check voltage at battery. With this new alternator I was getting 18 volts. Seems higher then what I want but at least it is charging. So I shut everything down, normal up wires on alternator, reconnect voltage regulator and start it up. Check voltage at battery and it is only battery voltage, no charging. Shut it down, and as luck would have it found another voltage regulator in the small pile of parts that came with the Jeep, tossed it in:

Started up Jeep and now I have charging at the battery!! Except that it is 18 volts at the battery. Only ran it for 30 seconds or so. Shut it down, checked a few things, started it up again and now NO charge at the battery. I am assuming the higher voltage and or amperage burned up the voltage regulator.

Sorry for the long post but now what do I do? I now have an alternator that wires in and fits but I believe is putting out to much and have two (I think) burned up voltage regulators.
I wish I could have just bought the correct 35 amp alternator but it doesn't seem to be available? All the places on line that list it, when I call to actually order it, they say, that is discontinued.

Any help would be awesome.

 

[MrPolecat]

Disclaimer: I am just a shadetree mechanic (if even that), so anything I say may well be completely wrong!

According to my vague understanding, linear voltage regulators work by gating the excess power to ground. This leads me to think that maybe if your regulator isn't grounded well, that might account for the excess voltage you're seeing at the regulated end. That is pure speculation on my part, but might be worth poking at with a continuity tester.

Also, your electrical system will only draw what it "needs" from the charging system, amp-wise. So the "output" of the alternator shouldn't be burning up your regulator (indeed, the you may see like 75 volts on the stator side of the regulator at high engine RPMs, so it ought to be able to handle 18v at idle). However, if you have a load on the regulated side that is higher than what the regulator can handle (such as a possibly intermittent short circuit before the fuses, or a flat battery of a larger capacity than the charging system is designed for), that can cause the R/R to overheat and burn out. But this is also uneducated supposition on my part...

I should reiterate that I probably don't know what I am talking about, but those are the things I would check for first......... Hopefully if I am way out in left field here, someone who does know what they are talking about will come along and correct me....

 

[mstar]

The alternator in question is the OEM Motorola unit with external regulator.They are obsolete but parts can be found.If he is retaining it for originality I would look to a rebuild shop.We have a shop in our town that
work on those.If not he can replace with a Delco 10si or 12si internal regulator alternator with one wire or two wire hookup.The Delco bolts up with no mods and works very well with higer amp rating if needed for electric winch,cooling fans,etc. I will offer a picture of the Delco unit installed on my 1969 CJ5.Originality is good so just letting you know what the options are if he wants to go another route. mike