Tony
Cal Spa, with 2100 control unit
Minnesota

My question is my spa will only runs in high speed mode, will not just run in circulate. Turning the jets off only turns them off for a few seconds, then it start back up on high. It recently had a OH code, went down to 45 degrees, then I turned the power off, it reset and is reheating, but only runs on high, not circulate mode. ????

Measure voltage from white red and white black to the pump plug on the side of the controller - (change speed settings while you do it).

Interesting, I just worked on an exact same spa two days ago, with the opposite problem - would work on low speed, but not on high. Circuit board failure as the cpu was keeping the low speed relay turned on 24/7 which resulted in major panic for the main pump - ie high and low speed simultaneously.

Check to be sure you're getting voltage to the motor on low speed. If so, then you need a new pump or pump motor, if not, then you'll need a board.