Tractor quit under load and now won't start

[Eugene]

Since you have a multimeter, you don't need a test light. Multimeter will tell you more than a test light.

Let's start with a voltage drop test. Charge the battery up, then let set for a couple hours.

Battery connected to starter. You can do this with the ignition switch off. Digital type, numbers not a needle, multimeter set to 20 volts DC. One multimeter lead connected to each battery terminal. Read battery voltage. Attempt to crank engine for a couple of seconds while reading the multimeter.

I'm assuming it's still a 6 volt battery. If battery voltage drops to and/or below 3.75 volts during the test, need a new battery.