Omega Heat Pump

Good morning all,

I have an Omega heat pump, that heats my pool like all get out. My problem with it started at the end of last season.
It is one that you turn the nob, get the pool to the temperature you want, turn the nob back, and voila!, it maintains the temperature within 1 degree. At the end of the season, it started not shutting off. It would heat, but not shut off, so if you went and manually shut it off, it wouldn't start up again unless you did it manually. A neighbour had heater troubles as well, so she had a techy come, and he looked at mine as well. He said it was the thermostat switch. He ordered it, but was only able to install it after the season was over. We started it up the other day, the pool got to where it needed to be, and I shut it off. SAME problem! I'm a hundred miles and two ferry rides away from the nearest tech, I really don't want to have to call him here if I can help it. It would cost me $500 before he ever fixed it. Any suggestions on what it could be, how to fix it, or is it something I need to just deal with and turn it off and on all the time manually?
Thanks for reading my little rant!
Mar