So no voltage at the coil+, C-101

[Reddart 207]

Well, intermittent voltage at the +coil. Runs with a wire from +battery to the coil +. 
 

so this means bad ignition switch, or possibly a wonky PTO switch? Could it be something else?

 

 

[tunahead72 2,412]

Off the top of my head, seat switch?

 

Edit:  Have you looked at the wiring diagrams for your tractor?

 

Edited November 16, 2022 by tunahead72

[gwest_ca-(File Mod) 11,041]

When the pto is OFF one of the pto switches should power the ignition.

When the pto is ON the seat switch powers the ignition with operator in seat.

Click on the picture  for more.

 

[Reddart 207]

The previous owner bypassed all of the other safety switches, not sure about the pto. 

[953 nut 55,220]

I would clean and tighten all of your electrical connections including grounds. There is probably a wire terminal that is loose or corroded causing the problem.

[Reddart 207]

I noticed the lights also don’t have power, so either at or before the ignition switch. 

[peter lena 8,625]

@Reddart https://www.harborfreight.com/18-inch-low-voltage-multi-colored-test-leads-66717.html?ibx_source=cdo4c90elb9bn7fecpcg&utm_campaign=email_productabandonment_cust_1_of_3&ueh=66052de9db0ecd8590ce04d

 have any of these ?  agree with @953 nut  on possibilities ,  makes connection issues much easier to find , pete

[rmaynard 15,457]

It's a C-101. First thing to check is the ground connection between the battery and the frame, and frame to the engine cradle.

Edited November 16, 2022 by rmaynard

[rmaynard 15,457]

2 hours ago, Reddart said:

The previous owner bypassed all of the other safety switches, not sure about the pto. 

Therein may be your problem. Previous owner bypasses are not only unsafe, but were probably done to have a quick fix to a problem, and that quick fix may have come undone.

[Pullstart 62,851]

Sounds like a good job for a DVOM 

[Reddart 207]

Frustratingly, the tractor ran last night without the Hotwire, so I wasn’t able to try to trace the circuit to isolate the problem. 
 

I had gone over the grounds last year, so I don’t believe this problem to be the ground, though I guess it’s always possible something has gotten loose since then. 

[953 nut 55,220]

22 hours ago, Reddart said:

 

I had gone over the grounds last year, so I don’t believe this problem to be the ground,

Glad to hear you have already taken care of your grounds, too many people seem to think they are unimportant. If the problem goes away with a hot wire it is probably not a ground since that would crop up with a hot wire too.

[Reddart 207]

1 hour ago, 953 nut said:

Glad to hear you have already taken care of your grounds, too many people seem to think they are unimportant. If the problem goes away with a hot wire it is probably not a ground since that would crop up with a hot wire too.

Oh yeah, grounds are very important. I have learned that from my other hobbies: