Have a Vita spa model Duet everything works except no heat. Temp control or thermostat clicks on and off when increased or decreased, still no heat.
Any ideas where I can begin troubleshooting?

Try check with the heater on your control system, maybe it's burn-out.

you mean iside the steel box on the cct board? I have voltage at the i/p to the element...

Ok I filled it. Jets work air valve works or shuts off. Using thermostat sw I can increase till system turns on, but leave it running and it doesn't heat up.. First off what i/p voltage should I have to the element ? I have 115 vac. When I turn down the sw it goes off. heres photos of inside the control box... in the 1st photo what is that a sensor on the o/p line halfway up?

Thanks to anybody in advance Brad

the vita spa duet doesnt have a heater. it has a coil around the pump and uses the pump heat to heat the water. if everything works on it try changing the termostat.