I removed the cover over the reset buttons and discovered that one is for 12v side
and the other is for 120v side.
I thought everything under that cover was for 12v! NOT.
The fusible link on the 120v T-stat is burned out.
NO idea why yet.
Will be removing and visually inspecting my heater element and then go from
there. Possibly a pinched wire or even lightning strike.
Probably just a shorted heater element. Still wonder why it burned out the link instead
of kicking the breaker.
As far as I know it worked last season.
No heat this year 1st time we tried it.
I'm sure it was not turned on while empty.
See the picture here
Thanks for all your help!
Now I'll do some more digging to try to figure out what burned this out and
then I'll be looking for parts.
It's 35 deg and windy today so I'm done for the day!
Retirement is not supposed to be this much work!!
Thanks again everyone!