Miata Fan issues

Cooling fan issues, not issues with people who like the answer
(Interestingly, I'm pretty meh on it. Neither here nor there.)

AC fan works when AC is blowing, no problem there.
Main fan works when I jump the connectors. Also works in occasions like today when the cold knocked out my battery.
Car clicked a few times but didn't fire, then the main fan came on until I went full counterclockwise with the key.
Other than those two instances, main fan refuses to activate.
I own a multimeter, shamefully don't really know how to use it.

Thoughts on where to start, possible causes?

Year? Anything weird we need to know, such as a diesel MB engine or an aftermarket engine computer?

95, no engine/electronics mods.

The main fan is triggered by the ECU. I'd start with fuses, just because. Then continuity.

The fact that the fan did something weird when the car wouldn't start could have been a low voltage issue, but it could also be indicative of a ground problem.