M9000 no start usually

[OkieJohn]

the tractor belongs to my Brother-in-Law in Cleveland, Utah.....
I happened on the scene returning home from Montana to Oklahoma, and found both of them down with Covid.

time to cut hay next week, Greg is scared out of his gourd....

1) IF cold, and sitting for a day/week, the M90 will sometimes start up normal.
shut it off, and the 12Volts to the Switch 'B' Terminal disappears.... and it won't return for days....

2) Today, replaced bad Negative battery cable, polished ground lug, secured and coated with Dielectric Grease.

* Wire brushed ( post cleaner ) both battery terminals, and inside new cable terminal and the OEM Positive terminal.
* Light coat of Dielectric Grease on all, tightened and secure.
* resting battery measures 12.75 VDC but no 12V at Switch

Obviously it won't start.

I have searched the web for help on this gremlin and there is not a single comment from Google referencing this exact condition.

I really appreciate some help on this.

Me? Retired Electronics Technician, worked in the Communications world since 1958.
My noggin is still working good, but the heat puts me down in about 15 minutes, so my Trouble Shooting time in 105* Utah heat is very short.

At 80 years of youth, heat is not my friend anymore.
Thanks to anyone who can help me sleuth this problem out.

Temporary Fix:

I am installing a Spring Loaded Toggle direct from Battery Positive Post ( thru fuse ) and connect it to the Switch 'B' Terminal. I don't want to leave it this way, but the hay has to be cut now.

 

[OkieJohn]

one extra comment:
a Kubota tech came out from the Salt Lake Valley, 3 hours away one way.

He replaced the Ignition switch, it started once and he left....
many 100s of dollars for nothing, that low life did not bother to make sure it would shut down, and restart.

to say that Greg is some kind of aggravated about that, don't quite cut it. He is an "ex" Marine, trained in Electronics and used to be a Navigator in F4s, he is a retired Supervisor for Utah Power and Light power generating stations.

He knows wires and testing, but Covid, a broken hip, and spinal surgery have him knocked down hard.

Oh, he told me there is no such thing as an "ex" Marine, he is a Marine through and through.

 

[Dave_eng]

Are you working from a Shop manual? i.e. WSM
Without you are just working blind.
You can download a free manual at Kubotabooks.com
Kubotabooks link
I have attached one page showing the start wiring system. I note a slow blow fuse and a smaller 20 amp regular fuse both feeding the key B terminal.
are you familiar with slow blow fuses?
A Slow Blow will be located close to where the main battery + meets the starter.
Any poor connection there any nothing will work.
This is what a slow blow fuse looks like.

This is where the slow blow is located.

Dave

 

[OkieJohn]

yup,
the slow blow is a 50 amp, sounds a bit big to me.

Very familiar with Schematics, that is why I included my personal history, blueprints, etc.

I downloaded the WSM and have several Images that I am working from.

this is the starting circuit that I think belongs to the M9000
I see that it is the same as yours after I downloaded that.