I have bought a house recently that came with a 1996 or 1997 Sundance Suntub. The spa pack was out of the spa and sitting in the garage. I put everything together, filled it and turned the spa on. Everything works except the spa doe not heat. In economy mode the spa does not heat during the filtration cycle. In standard mode the spa will not turn on to heat. I have tested both the temp sensor and the high limit sensor with a multi-meter and a reference chart for ohms/degrees and found no problem. I also tested the flo sensor with the pump on and it does close the circuit. Any advise about how to fix my spa will be greatly appreciated. Thanks!
Found the problem. Ended up being a damaged wire between the top side control and control board which was the power wire to the temp control knob. I soldered it back together and poof the spa is now heating.