HotSpring Spa '06-current Hi-Limit. This High Limit Thermistor is a safety device that will shut down the heater if the water temperature exiting the heater is too hot. This would indicate a "low water flow" condition. It is used on all 2006-current Hot Spring Hot Spot Mallorca, Hot Spring Hot Spot Sorrento, Hot Spring Hot Spot Trinidad & Hot Spring Hot Spot Tobago spa models. It is also used on all 2006-current Hot Spring Solana RX, Hot Spring SX & Hot Spring TX spa models. Notice: The older style has two blue wires; the new one has two wires in one gray enclosure.