Does this happen with the key switch in the ON position or the START position?
I just got back to this today.
When I turn it to ON, all three lights turn on, but the glow plug light goes off right away. In the START position, only the other two lights are on.
The battery is from 2019, but it tests okay, and when the tractor cranks, it cranks strongly. The terminal connections look great.
The shutoff solenoid is looking pretty crusty, so I am replacing it. The tractor started once today, and I had to stop it manually because the key did not work.
I crawled around under the tractor and removed some of the covers from the dash area. I have seen no sign of the plunger switch yet, but I will use the photo provided above and see if I can match it to anything.
I would like to check the ignition switch. I can't figure out how to remove it. It's also hard to get the dash out.
I found a nice mouse nest under the rubber cover by the clutch, but I could not find any chewed wires.
It looks like they made some changes to this tractor during its run. That must explain why it takes a Los-Alamos-level research effort to figure out whether there is an HST safety switch.