Is it working?

I don't really know what to say, other than, "why?"

There's a few problems, but as long as you put your fingers in the water before jumping in (In case it has gotten too hot), you should be OK.

Oh, and when your circ pump eventually fails, things will get interesting. The temp sensor isn't on the heater output, it's on the circ pump intake.

I have no idea why someone popped in a D1 heater instead of the Hot Spring heater, but if you plan on keeping it, you should ditch the D1 heater, and get the Hot Spring one, and then fill in the hole in the shell.

Ordered a new heater last night. also found an exploded view of the pump and could see where the sensors fit as well. Looks like it "fits" much better as well. I have a floating thermometer in the tub as well, and always will. Thanks for the help and I should have the new heater by the weekend so I can replace it. Thanks for the advice.