Hot Tub Compatible With Watkins Spas Thermostat, Control, Hot Spring, '94 Retrofit 75087This Electronic Control Thermostat (thermistor included) replaces the mechanical thermostats in the 1994 Hot Spring Classic, Grandee, Highlife, Jetsetter, Prodigy and Sovereign spa models. This retrofit remedy was introduced to solve the mechanical thermostats high failure rate in this model year Hot Spring. Due to the backflow of electricity from the relays, the mechanical thermostat's contacts would quickly fuse together causing it to fail sometimes