Re: Cub 12V conversion problem

Fri Oct 25, 2013 5:42 pm

[quote="ibrake4rust"]Linemen get killed all the time working on high voltage transmission lines. But you'll never get killed changing a fuse on a tractor unless it runs over you

:bellylaugh: Or the lineman does... :bellylaugh: :crazyline:

Re: Cub 12V conversion problem

Fri Oct 25, 2013 7:03 pm

In thinking about the reported incidents of melted “battery” conductors on alternator-equipped vehicles, it seems to me, and I am entitled to my opinion, that the likely cause would be a shorted stator in the alternator.
In my opinion, the alternator could not deliver sufficient amperage to do that kind of damage to the conductor unless it also seriously damaged the battery- boiling out electrolyte and bulging the case. And I just doubt that it can deliver that kind of amperage -period. The more likely scenario is that the stator in the alternator shorts and grounds, resulting in high amperage from the battery flowing to the alternator.
I have not seen that condition occur and thus have not tested nor diagnosed the problem. And I am not new to alternators. I bought a new Chevrolet in 1963, the first year for alternators on Chevys. And it failed because I removed a battery cable while the engine was running. Ruined some of the diodes. I don't remove cables on running engines anymore.
While I do use 10 gauge for the “battery” wire from the alternator for the conversions I do, I have personally tested 12 gauge wire conducting 100 amperes for more than an hour without burning off the insulation-- but it did get hotter than one wanted to touch. The largest alternator, bought at the wrecking yard, I have installed on a tractor is 70 amperes and I used 10 gauge on it-works well and charging rates above 30 amps have been for only a few seconds duration at a time.
If I was going to use a fuse, it would have rating a little larger than the rating of the alternator to avoid nuisance blowing at moments of high charging rates. Using one of lower rating than that of the alternator in the “battery” wire just is not rational.
And that is my opinion.

Re: Cub 12V conversion problem

Fri Oct 25, 2013 11:36 pm

Boss, the fuse will protect the alternator, the wiring and the battery in case something fails.
Fuses or fuse-able links are used in cars and tractors in all modern applications, if someone is going to upgrade to an alternator I think it's a good idea for protection. I have included the wiring diagram for my Kubota to show how its used between the alternator and the battery.
On Bus Driver's comment about the size of the fuse:
We've been talking about Delco 10 63 Amp, Hitachi 14321 35 amp and the Hitachi 14255 50 amp alternators. On Farmall tractors about the highest RPM is 1600 (this is where the drawbar horsepower tests are done) and with a 1.92:1 ratio on the crank to alternator pulley, the alternator rpms is about 3000. At 3000, these alternators will output approximately 60% of their rated output At 3000 rpms, the Delco 10 is 38 amps, Hitachi 14231 is 21 amps and the Hitachi 14255 is 30 amps. So I think a 30-40 amp fuse is about right for a Farmall tractor using on of these alternators. If it blows for no reason, I'd replace it with the next higher fuse.
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Re: Cub 12V conversion problem

Sat Oct 26, 2013 6:36 am

I bypassed the light switch, but the ammeter readings were the same. Checked the new ammeter for short and found none. I have 12v bulbs for the lights when re-installed. My electrical skills are elementary and I could use some tips about what to do next with the wiring or testing for faults. Many thanks.[/quote]

Sorry about the babble connected with your post....The point I was trying to make is, if you decide to use a fuse, WHICH IS ENTIRELY UP TO YOU, just be aware that it MAY BE hot after it blows...People do trouble shoot with an engine running...And the pulley and fan are nearby :oops: ...Never having fused an alternator on a tractor or knowing anyone who has perhaps a location for easier changing of the dreaded fuse could be envisioned, instead of having it close to the lug...The schematic John provided is the norm for 3 wire hookups...Boss has a how to, to make it one wire..both guys are very knowledgable...Just take the information and do what you feel is right, after all its your tractor....And by the way Welcome to the forum....Sorry about any negative vibes on your post..This electrical thing is ongoing it seems... :lol:

Re: Cub 12V conversion problem

Sat Oct 26, 2013 2:17 pm

Many thanks for all the advice offered. I moved the wire as directed by Gerry and the problem is solved. It looked like it would be a booger to get to in that tight space, but I loosened the switch mount and was able to rotate it enough to access the terminal screws. Result: no discharge with switch off, discharge when on. Bus Driver, I actually did this before reading your post, but the wire was already at the switch anyway since it is an OE or equivalent wiring harness. Now I have to go to town to get the diode before wrapping up. It has been educational (and amusing) to read all your posts. Thanks again, to all.

As help for anyone else thinking of such a conversion, you can use the existing mounting bracket, adjusting bracket and belt. Flip the adjusting bracket over and attach if backwards (not end to end). You can bend it a little in a vise if you need to, which is easy. Use a long 5/16 bolt through both sides of the mounting bracket and both ears on the alternator, with the forward ear being forward of the forward ear of the bracket. Maybe one or two washers for perfect line up on the belt. The ballast resistor mounts handily on the rear end of the 5/16 bolt. Not finding a bolt of the exact length needed, I used a longer one, extended the threads with a die and sawed off the excess. Photos attached. (Yes, I know, I will put a protective cover over the exposed Bat terminal on the alternator).
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Re: Cub 12V conversion problem

Sat Oct 26, 2013 3:26 pm

Here is what I like about the one pictured above. It uses a "2 point mount", both of the mounting ears are fully supported by the bolt. I do not like the instances where just one ear is used as any variation in the belt causes the alternator to wobble as the belt runs.

It is pleasing to know that my suggestion about powering the exciter from the coil terminal was understood.

Re: Cub 12V conversion problem

Sun Oct 27, 2013 7:48 am

Nice clean Job.... :applause: :thumbsup: Dave

Re: Cub 12V conversion problem

Thu Nov 14, 2013 10:53 am

Thanks, Dave. This thing starts so quickly now that I can hardly release the starter pull fast enough.