Just installed a solar heating system - Heliocol panels with a Hayward GL235 automatic controller. System is working as expected except that the controller is shutting off the solar loop when water temp reaches about 82.5 degrees no matter what the controller setpoint is set to. I checked the voltage levels at the sensor input terminals and they looked OK- collector temp was well above the pool temp and setpoint was well above pool temp. Conditions should have caused controller to engage solar loop.
Any suggestions as to what might be wrong?