Kubota ZD28F Starting Issue/Safety Switches

[dawson19]

So here is the long rundown of what i have been experiencing with my Kubota ZD28F (72inch if that matters). My brother in law and I are stumped....

For about 2 months now I've been having an issue with the PTO lever. Sometimes i would sit on mower and it wound crank right up with no issues at all. Sometimes i would have to engage/disengage PTO a couple times while turning key to start mower. Naturally i suspected a bad/dirty PTO safety switch. I bought said switch and installed it. Now the mower will not start or turn over at all. We suspected another safety switch issue after testing things (starter is fine, brand new about 6 months ago, still getting proper voltage). Mower will also start if the key is in ON position while we hot wire said mower.

Anyway. We looked over all fuses, wires, groundings and all seemed fine?

I installed a new parking brake safety switch just from a forum hunch, didn't solve the issue. It was just our next best guess. Didn't fix it. I had a spare safety switch so we tested this new safety switch on arm safeties and again on PTO switch by removing, installing, trying to start. No luck.

We have jumped the seat safety switch. No luck. Also have installed a new ignition switch thinking MAYBE that could be the issue. No luck there either.

I purchased a new Control Board (part#k3111-62510) since the dealer said that may be the issue, whew expensive. Installed. Still no start.

Without taking this thing to a dealer for diagnosis what in the world could we be missing?? Has anyone else been absolutely stumped with this machine? Mower is in excellent shape, always garage kept and only used on two yards its entire life. I did have the starter go out on it 6 months ago but besides that no issues within the last year. At this point I've thrown enough dumb money at it, its time to ask the experts (Ya'll). Thanks for any help whatsoever.

Its just very odd that this machine was starting when i would jiggle the PTO switch but now that I've replaced the safety switch there's nothing.

ETA: Battery is fine, less than a year old. when turning the key all lights come on as they should along the side panel, just no turn over of engine

 

[Hugo Habicht]

I would check the switches first using a simple voltmeter instead of embarking on an expensive parts replacing operation. Establish facts and do not replace "maybe" parts.

Since you have replaced almost everything that only leaves the wiring with connectors (don't even think about replacing that) and the starter motor itself.

Check if voltage is present on the starter solenoid (the thin, not on the fat cable). If not check voltages on all the switches. Check on the control board or its connectors, that includes the switch wiring.

Since the PTO switch was working intermittently before you replaced it focus on this one. Try if it starts with PTO engaged, maybe the wrong switch went in (normally open / normally closed). Check if it is adjusted properly with a voltmeter across the two pins, this must change when you engage the PTO.

What you need is schematics which may be in the operators manual or in the work shop manual.

 

[dawson19]

I would check the switches first using a simple voltmeter instead of embarking on an expensive parts replacing operation. Establish facts and do not replace "maybe" parts.

Since you have replaced almost everything that only leaves the wiring with connectors (don't even think about replacing that) and the starter motor itself.

Check if voltage is present on the starter solenoid (the thin, not on the fat cable). If not check voltages on all the switches. Check on the control board or its connectors, that includes the switch wiring.

Since the PTO switch was working intermittently before you replaced it focus on this one. Try if it starts with PTO engaged, maybe the wrong switch went in (normally open / normally closed). Check if it is adjusted properly with a voltmeter across the two pins, this must change when you engage the PTO.

What you need is schematics which may be in the operators manual or in the work shop manual.

Thanks for the quick reply. I’ll definitely start retracing my steps and start there. I thought the simple parts would be the issue with the intermittent working. But naturally one can rarely get that lucky.

Attached are the images I was going through and using for diagnosis. It’s got to be something simple I’m just over looking. (I hope)

 

[Hugo Habicht]

Do you have a multimeter? If not buy one, a cheap digital one can be bought for under $20 and they are pretty good. Just unplug the switches and test the resistance individually, lowest Ohm range.

And the switches I know need adjusting mechanically, so you have to put them in that the switching point corresponds with the mechanical movement. Check that since after replacing the PTO switch it never started any more.

And make sure there is enough margin in it. So PTO released there should be low resistance (switch closed, close to 0 Ohms) but when you engage the PTO make sure the switch stays closed for a bit of lever movement, not that it opens when you barely touch the lever, otherwise you may get intermittent faults again.

 

[GreensvilleJay]

one test to do.
remove connector on PTO lever
connect DMM to the switch (need to make extender cables for meter of course...)
set DMM ot 'beeping OHMS'
move PTO lever on-off-on-off
DMM should beep when switch closes.

If it doesn't ,then you'll have to bend the 'tab' on the lever to push the plunger on the switch or adjust the position of the switch

 

[whitetiger]

Here is a wiring diagram for your ZD28.

 

[GreensvilleJay]

pretty sure, well mostly, kinda.. that you can get the WSM from WWW.kubotabooks.com