Alternator Hot Wire

I have never had to mess with a stock alternator. The DSPO removed mine before I got the truck. But, I am going to try and use Pistolnut's 24V alternator on my M35 to replace the external regulator generator on it. The only problem is that Pistolnut said it overcharged.

So, I decided to test it on my alternator testor in my class. This is a machine that has a motor, belt and pulley along with a sliding mount for alternators. It has a bunch of wires and switches making it able to hook up to all kinds of alternators. It even has a gauge for amps and volts. The gauge only goes up to 18 volts and the console can only supply 12v.

Then I decided to hot wire it on the machine. Using the machine to turn the alternator and using a 24v battery charger for a source and a multimeter to read the output.

I put it on the machine, connected the alt ground cable to the negative on the battery charger. The positive on the charger to the small wire on the alternator. I turned the machine on and it started turning. No volts were showing at the big bolt where the big alt supply wire goes. Then, click! and the motor lugs and the speed reduces a lot. But, 2 volts were showing and the my machine couldn't turn it any faster.

I reversed the positve connections and got nothing until I touched the small wire to the big wire bolt. Same result with the load on my machine. It couldn't turn it.

My question is this:

The small wire with the Packard connector is the alt exciter that turns it on while the big wire that bolts on is the positive back to the batteries, right?

I am going to take it home and install it on the Gasser. I don't want to burn up my good Optima red top by getting my wires backwards. I will check the output if my Gasser can turn it. Hopefully, the litte hex bolt will adjust the output to what is required.

What is the required charging output?

Thanks.

I'm pretty sure its 28.8v, I might have seen 30 mentioned.

They will put out between 24-30V. 28 being optimal. I don't understand your machine not being able to turn the alt that kinda puzzles me. ??

BTW I have a GI kit replace the generator and voltage regulator with an Altinator let me know if your interested. It was designed for M35s.

Let me see if it bolts up before I start thinking about a kit. Since I am going to rewire the entire truck, I just need to make it line up with the pulleys.

It should bolt right in since they are the same size...the question is does it put out!

Joe, I don't normally joke that much, but if this were the BS board I would be all over your last post.

I just don't know if it works or not. I will be prepping and painting the last little bit on the 715 tonight and tomorrow and I have to go to Houston for my grnadmothers 90th b-day Sunday. So, it may be next week before I find out. I am months away from needing it anyway. I just need something on there that holds the water pump belts tight while I move it around the yard doing restorative work and that won't change until it is all painted and has 10 good tires under it.

But, am I right about the wires? Ground is ground. The big wire is to the battery and the little wire is power through the on/off switch, right?

Your wiring is correct...and in fact, if my understanding is right of Mil vehicle wiring methods, the wire tags should read:

468----excite wire
5------alternator charge back to batteries

Tim, did you try hooking the battery positive to both the big terminal and the little wire, some of the old alts needed the voltage there as a reference to generate more...not sure if that is the case with what you have or not..but without a wire on the big pos term it may not have a reference so, it may not make any voltage, kinda like some cars won't run without a battery installed, even if you pull the battery while the car is running...regulator is there to regulate what it sees, without the input, it doesn't do anything..maybe clip the meter on the big terminal and hook 24V + to both big and little excite wire , ground to ground and start to spin it, see what it does..isn't that the way it would work stock in the truck?

40G is on to something. If you look at the wiring in any mill truck you have the big wire that goes to the batteries it has 24V on it either from the batteries or from the altinator when it's spinning. The excite wire gets 24V when the on off switch is turned on. So you may need to put 24V to both wires and then set it a spinning.

I tried the way Mark and Joe described. Actually, I had a student switch it. About the time it clicked on and started making voltage, the positive battery charger cable came into contact with the case of the machine. Which of course caused sparks and the handle plastic to catch on fire. I had students running all over the room thinking it was going to blow up or something. It amazes me how scared some people are of a little fire or a few sparks.

I bolted it up to the Gasser tonight and it won't work. The Gasser has really big V belts compared to the M715 version of V belts. I tried swapping pulleys, but the shaft of the alternator is huge compared to the generator shaft. I was taking a break from paint prep on the M715, so I just put the generator back on so I could still drive it around over the weekend. I might chuck the generator pulley up in the lathe and try to cut bigger groves. Which means I am going to have to figure out all those gears for the feed speed on my lathe. It won't be the next few days.

if it's overcharging, it's most likely one of the diodes inside is shorted, it's conducting all the time, versus only when it's supposed too...not too hard of a fix, I think you could do it..that old of equip, it should be bolted into one of th endbells...

I've always been told that the M-35 alternator and the 715 one are the same. I have a spare M-35A2 unit, maybe a pulley swap is required?

I also understood that the M-715 had an alternator. If so and the M-35 are the same, then the M-35 should have one as well. I got in a lengthy discussion about this with a former Army motorpool sergeant at work yesterday and he insisted that the M-35 uses a generator. I looked at my spare unit and sure enough, the data plate calls it a generator. Can someone clear the air on this? I have no power output on my M-35 so I was planning on swapping in my spare. If it is a generator, how do I flash it to excite it?

how many terminals does it have? and relative size of the terminals?

You should never hook up an alternator to a battery charger alone. The sensed voltage is higher than the output and you're trying to force amps back into the charger. It is best to only use batteries to test alts, preferrably good and charged batteries at that.