Limit Switch Replacement — Part Numbers: 420010063S, 420010064S, HMXHLI2932, HAXHLI1930, STA1516255 Key benefits Restores critical overtemperature protection for pool and spa heater electrical systems. Prevents heat exchanger damage and unsafe operation by stopping flow when water temperature exceeds safe limits. Direct replacement for the listed part numbers, simplifying and minimizing downtime. What it does The 420010063S limit switch (135°F) detects when water temperature rises beyond the safe threshold and automatically opens the heat exchanger outlet to interrupt operation and protect the heater. Provides reliable, repeatable activation to reestablish factory safety function in compatible heater models. Compatibility and fit Replacement for Pentair StaRite limit switches used on MasterTemp and MaxETherm pool and spa heaters and compatible electrical systems. Matches the listed part numbers: 420010063S (135°F), 420010064S, HMXHLI2932, HAXHLI1930, STA1516255. Intended as a direct replacement for the original switch in the listed models without changing the heater's wiring or mounting. Performance and attributes Safetyfocused function: opens the heat exchanger outlet automatically when overtemperature is detected. Designed for use in pool and spa heater electrical systems where reliable temperature sensing and protective action are required. Consistent operation restores the original thermal safety behavior of your heater. Typical applications Emergency : a failed limit switch to immediately restore safe operation after a heater fault or shutdown. Preventive maintenance: Swap in a switch during scheduled servicing to ensure continued overtemperature protection. System restoration: Reestablish proper safety control after component failure or when refurbishing older Pentair StaRite MasterTemp or MaxETherm units. Customer service We aim to meet customer needs with reliable replacement parts and clear support. If you have questions about compatibility, installation, or performance, contact our customer service for assistance. Our goal is to provide a straightforward product experience and dependable service for every .