Deere 4100 - Is there a way to check indicator lights?

[RMJ22]

In particular I want to make sure my temperature light in the dash works and will come on if my engine were to overheat. It does not come on briefly, like some lights do when you turn on the key, to let you know its working. How can I test it to make sure it is indeed functioning. FYI - my tachometer is not working, so I'm just wanting to check other lights. I know my hazard/flasher light and pto indicator lights do work.

And I would like to periodically check my engine temp with an infrared thermometer. What would be ideal operating temperatures and where should I point the temp gun?

Thanks in advance!