weird electrical problem - no hydraulics

[BullCreek]

I have a JCB midi cx tractor/loader/backhoe that has developed a weird electrical problem. It first manifested itself as reduced cranking power (acted like the battery was weak when it wasn't) and eventually progressed into immediately blowing the 40A fuse when I turned the ignition switch to start. The starter had some corrosion on it, so much so that the post broke off when I went to clean it so I replaced the starter hoping that would fix it - but same problem - immediate fuse blow. At some point I realized if I left the alternator disconnected, it would crank over fast, start, and run normally without blowing a fuse.

I had a lot of work to do so I used it that day with the alternator disconnected - no troubles. Eventually at the end of the day, the battery ran down as expected. I put it on the charger, took it out the next day expecting to work - but alas - the machine started fine but the hydraulics to the ioader and hoe are dead (forward rear drive still works so pump is working). In the meantime, I took the alt off and took it to a repair shop thinking they would find something but they said it was fine. I hooked the alt back up connected to the starter/battery - thinking the short would return since no repairs were made - but it did not. At this point I'm really puzzled - and wondering if the short hasn't been in the hydraulic system all along. Back last fall the same thing happened to the drive system (tractor ran fine but wouldn't move) - I fixed it by checking the fuses and replaced one of the 20A fuses to the hydraulics that was blown. This time I can find no blown fuses though.

Any ideas? The loader and hoe are on the ground so moving the machine will be difficult - and my dealer will charge plenty for a farm call. They sent me some of the wiring schematics but unfortunately not the part that has the hydraulics. I assume there is solenoid that maybe isn't being engaged to let the hydraulic fluid in maybe?

 

[Fuddy1952]

I'm a retired electronic technician, but all I can offer are a few suggestions based on what you said...I left the alternator disconnected, it would crank over fast, start, and run normally without blowing a fuse and- the machine started fine but the hydraulics to the loader and hoe are dead, as well as the starter terminal corrosion/breaking off.
So my guess is having those problems it's probably a multitude of things, maybe exposed to water?
The first thought is you diagnosed the alternator blowing fuse, draining battery (hard starting), for whatever reason the alternator shop checked and it was ok (maybe just a quick check?). You'll need a schematic of hydraulic electrical system which must be where problem is, as you said solenoid. Without schematic it's working in the dark not knowing how it's designed...relays, etc.
I'm thinking you'll find more areas of corrosion besides just starter.
One easy test thing to rig up temporarily is disconnect one battery lead, clip in a headlight with jumper cables. Light should be off...key on light may light depending on current draw. Move wires, flip switches, etc., if light comes on bright that means a heavy current draw. If light comes on wiggling wires you should be able to pinpoint it to a short (insulation worn...rubbing frame).