I have an old Discovery Spa with a Balboa 27100 circuit board and an analog control. Everything works well until it heats to a certain point and starts cycling the pump and heater on and off. First the pump starts then the heater comes on for a second and goes off. Then the pump stops(over and over). The thermostat seems to work, because I can control how hot it will get before it starts cycling. Also, it will only heat to 90 degrees when temp is set to the max. If I run the pump in fast mode, the heater cycles on and off in the same manner.

Any ideas?

Nevermind. Figured it out.