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Any help??
Swap the red and black leads which go to the jet pump. Then power up the spa, and let it go through it's start-up procedure. If the high speed pump comes on, then you know the control board is fine, and you have a bad motor (or the connections inside the motor may be wrong or loose). You can't run it for very long with these leads swapped because it will kick in the heater, and with the heater and the high speed pump running at the same time, it should trip a 15A breaker almost instantly, and a 20A breaker in a few minutes. Of course, if you turn it to high speed ('jets') and the low speed still doesn't run, then the problem is with the motor (motor itself or connections inside of it).