Pop's 1864 Cub's PTO blows fuses with belt on, doesn't with belt off...

[rhammond]

My Dad’s 1864 Cub Cadet (model 14A-684-100 sn: 894007) blew its first main fuse last week. Went through the wiring and fuses and the short story is that I can put a temp in line fuse right at the PTO’s harness input, along with an inline ammeter (car style +/-30amp) and attempt to engage the PTO… bam, blows the fuse and it swung to 30A briefly prior to that. If I take the deck and belt off, getting the side pressure off the PTO, I can repeat this and it only pulls its correct 4A. With the deck and belt off, I measure the windings of the PTO coil and its about 3ohm or so (that makes the 12V/4A make sense), and I measure about 50ohm from either winding to the engine (ground), with just the 3ohm difference between measuring one end of the winding or the other to ground. That all makes sense. I understand that mechanical load doesn’t matter to the coil of the PTO, but the side pressure apparently does (the belt’s pull on the PTO). Any chance this is a nicked wire (seems far-fetched that a few 10’s of 1000th’s of an inch movement would touch a nick or not), or is this a very common indication of mechanical wear causing a short (i.e., get a PTO and be done with it)?

The cub’s only got 450hrs on it and my 83 yr old Pop likes the hand operated hydro lever (doesn’t want to upgrade), so I don’t mind spending the money. Which brings up another thing… I see two or three replacement PTO’s out there. A couple of parts sights (including the link from ihcubcadet) says the PTO part number is 917-3403 (replaces 717-3403). From that, searching around for the parts out there, I see a Stens, a DB, and a Silver Streak that all look like they are made by the same manufacturer, and are a replacement for the original… and I see an Oregon that appears to be the most expensive… and I see an Xtreme that has high temp bearings (its slightly less than the Oregon). Any opinions?

 

[jdiederichs]

I'd pull the clutch and break it down, my guess is the insulation is rubbed thru on the field coil where the wires emerge. It may be an indicator that the bearing is worn, these can be replaced. let us know what you find please.

 

[rhammond]

Hi Jim,
That would explain the side-force causing a short, where the belt taken off clears up the short. That's the best place for the short to be, versus down in the windings, eh? I'll take it apart and see (and take pictures).
Thanks, Russell.

 

[rhammond]

Jim,
Well, the old one's bearings were dry, sure enough, but not seized or broken up. The local dealer (good guys, owner and mechanic) were encouraging of both packing old bearings or sourcing new ones through local bearing house (Motion Industries)... but, the swollen and cracked winding housing was what the mechanic pointed out as a "we've rebuilt those a lot, but, we've never had much luck with PTO fields that were that heat damaged." They were additionally helpful about going through all their used parts stash trying to find a coil. No luck. Had one new one in stock and it was about the same as ordering and paying shipping... so, that got Pop running. Put some pictures on here (hope I got them uploaded successfully). Thanks for the info and help.
Russell

 

[rhammond]

Btw, the dealer looked for issues where the wires emerge from the coil, also. That all looked good. Like you said, he said that would have been the best failure to have (for fixing it inexpensively, that is).