B6100E Electrical Issue

[Welder_Zach]

Hi all,

My name is Zach and I have been chasing an electrical issue on my Kubota B6100E (1980 or 1981). This machine has been in my family since it rolled off the showroom floor.

Problem: The tractor acts as if the battery is dead. Turn the key either way and nothing. No lights, nothing. The battery is brand new and was tested at the store. I have noticed that if I put the battery on the charger for a few minutes, the charger will state that it is fully charged and have full voltage. I place the battery on the tractor, turn the key to the left and the light turns on for the glow plugs. When I go to turn the key to the right, it acts as if the battery is dead. I go to try it again and nothing. No glow plug light or anything.

Things that I have tested and/or replaced:
* New battery - Get fully charged voltage with a meter. Had the store test the battery and they said it is fine.
* The negative terminal on the battery cable was loose, so I replaced it. Verified continuity from the negative terminal to ground and the positive terminal to the starter.
* I tested the starter and discovered the solenoid was bad, so I replaced the starter/solenoid.
* The oil switch was damaged, so I replaced it.
* I measured the resistance of the clutch safety switch and it seemed high, so I replaced it.

Looking at the wiring diagram I feel like the only other thing it could be is the ignition switch and/or regulator. Both parts are a little pricey and was wondering if anyone knew how I could test these? I am not a savy electrical guy, but I know how to run a fluke.

Is there anything else I am missing or should be checking?

I appreciate any help.

 

[North Idaho Wolfman]

Everything point to the Main switch being bad.
You can confirm this really quickly with a meter or a test light on the switch terminals.

 

[Russell King]

I noticed that you discussed “negative terminal on the battery cable was loose so I replaced it.”

Often on these older tractors the battery cables have been cut and replacement battery terminals that clamp the wire have been installed. Those clamp the wire battery terminals are usually a corroded nightmare and the cable itself gets corroded under the insulation. The cable can pass continuity tests but can’t carry very much amperage and certainly not enough amperage for the starter.

You can do a simple test that proves the battery and starter are able to spin the engine, but it is somewhat dangerous since the engine could start and if the tractor is in gear you are in a position to be run over and crushed. So if you do this test be very careful that the tractor is in neutral and I would have a second person around in case things go bad.

There is a wire from the clutch safety switch to the starter solenoid. It is usually black wire with a white stripe that connects to the solenoid with a spade type connection. Remove that wire from the solenoid and then you will short the spade on the solenoid and the battery cable connection on the starter. There are easy ways to do that with a screwdriver blade but that will make sparks and you will be standing right in front of a rear wheel (asking to be crushed). A bit safer but also a little more work is to attach two wires to the tractor. One wire goes onto the positive battery cable connection so is a hot (live) wire and the other replaces the connection to the solenoid. Make them a few feet long so you are out of the way if the tractor moves forward. Then touch the two wires together to provide power to the solenoid terminal. The engine should crank. You don’t need to start the engine (but you can) so disconnect the wires if it starts to crank.

Remember the engine can start with the key in the off position on these old tractors so just touch the wires together, don’t twist them. You can wear leather gloves to protect your hands from hot sparks.

If the engine cranks the battery and starter and battery cables are all good and the problem is on the key switch side. If the engine doesn’t crank then I would replace both battery cables and clean up all four battery cable connection points. That would hopefully correct the problem.

Good luck and post back for more help if needed.

Wolfman’s test will be safer but not prove the battery side wiring.