Kubota L4200 Alternator not exciting

[kubotal4200]

I've been working on this tractor's electrical system for about a week now and feel like I'm close to having it fixed but I'm also nearing having someone else look at it really annoying problem. So the dash lights would flicker on and off and then one time you come back to start the thing it's completely dead.

This continued until recently when the alternator battery light no longer hardly ever came on any more and I never could get the alternator to charge the battery. Had the alternator tested by a alternator shop they said it was fine. No blown fuses i've checked em' pulled em out put dielectrec grease on them that's not the problem neither is the 40amp maxifuse.

Got creative and isolated the alternator from the tractor's electrical system but left it hooked up to the belt. Hooked it up to a older 12v battery that was readin' 9 volts with the positive running to the positive post and to both exciter terminals. I then grounded the negative to the alternator body and started the tractor with jumper cables from the bob cat. Nope nothing it just showed the volts of the battery on the alternator output but it wasn't putting out any..

So then I thought it must of been the alternator but after looking it up looks like a alternator exciter needs a supply of amps to work..and the alternator does kick on at high rpms with a 13v output

I then tested for amps to the exciter and found none.. so I'm thinking it's a ground issue either to the instrument panel(which i've taken apart looks O.K. minus the dust and some black oxidation but I didn't see any on the battery light circuit bulb.. tests fine(the bulb)
Also for awhile the coil light wasn't turning on or the lights (they started working again)

All this leads to my conclusion that I have a ground problem somewhere either in the exciter circuit or my guess is the instrument panel but I can't find it!! So many wires that change color as they go down the steering column/relays so my question is where can i find a decent Warehouse Service Manual for this tractor with electrical diagrams that's not a $120+ bucks I was hoping you all might know of a internet site that's not a scam where one could just pay for a lower priced download of manual or just the electrical section of the manual.

 

[oosik]

Welcome to TBN. Electrical systems are not my cup of tea. I'm sure there will be others that can provide the info you need. I know how you feel - I looked behind my dash once and knew it was a place I didn't want to go. Keep the faith, I'm sure its a problem YOU will be able to fix.

 

[skyhook]

The bulb for the "exciter" circuit ( in your dash ) does not ground out. One end of the bulb connects to the exciter on the alt and the other end (thats usually grounded) connects to the ignition key "on" wire. When you turn the key on, the bulb lights up (exciting the alt) after start-up, the bulb turns off, (if your alt is charging well). So to test this alt and bypass your dash alt light, you could install a single 2 wire bulb between the alts exciter pin and the other end of the bulb wire to your battery. Both wires on your test bulb go to a power source with the key on. If this works, then you may have a broken or loose wire leading to or near the dash alt bulb.

 

[kubotal4200]

Thanks oosik and skyhook I ended up buying a pdf service manual from tradebit for $14.. didn't really help any the manual had several models crammed into one book like usual seems like, so I guess they just spun a bottle to see which tractor's wire colors they'd use because my colors didn't match theres


Still for $14 can't complain once I realized that solid black was ground instead of green duh I followed the black wires down to a connector that was in a annoying spot it was a few inches off the floor of the tractor in a metal cavity with a plastic removable cover I removed previously got in there and just started taking em apart and one of them was corroded badly cleaned it off best I could and then I saw the battery symbol light up w/ key!

Went to test the alternator exciter wires by grounding them.. not to my frame as recommended but to the battery I read that if the tractor side wiring works then grounding it to frame should make battery light stay on if tractor side circuit is good .. so I turned the key to start, no lights at all uh-o realized I blew a 10Amp panel relay fuse replaced it.. thought well **** I'll just plug it into the alternator, it started up I read the battery, it was charging at a steady climb of 13+ volts just goes to show I should of stuck with checking the easier stuff first before I jumped to the harder stuff.

Next time I'm looking at a tractor though I'm going to take a harder look at how they run the wires and how weatherproof they are Kubota seems to make a solid tractor regarding the essential meat and bones like the engine but the placement of like the dipsticks and oil fill are just really not that great and you'd think they'd put a O ring around the instrument cluster circuit board.. Still can't complain just happy to be putting it back together rather than taking more off.