420020007S Control Board Kit for Pool and Spa Heaters What it is A replacement control board kit engineered to restore reliable electrical control and temperature regulation in compatible pool and spa heaters. Key benefits Improved reliability: upgraded solidstate capacitors and power chips plus precision soldering reduce component failure and extend service life. Robust protection: regulated power module and enhanced optocoupler provide overheat, overvoltage, and short circuit protection for safer electrical operation. Better performance: faster output control and more efficient power handling improve heater responsiveness and temperature stability. Direct replacement: designed as a dropin control board kit that interfaces with existing heater sensors and safety switches. Technical highlights Upgraded solidstate capacitors and power chips for stable power delivery. precision soldering for improved connection reliability. Improved optocoupler module for clearer signal isolation and control. Regulated power module with builtin overheat, overvoltage, and short circuit protection. Model number: 420020007S control board kit. Compatibility Compatible with the following pool and spa heater electrical systems and control boards: MasterTemp NA and LP series heaters MasterTemp 200 control board MasterTemp 250 control board MasterTemp 300 control board MasterTemp 400 control board MasterTemp 400HD control board StaRite MaxETherm SR200NA control board StaRite MaxETherm SR333NA control board StaRite MaxETherm SE400NA control board StaRite MaxETherm SR200HD control board StaRite MaxETherm SR333HD control board StaRite MaxETherm SR400HD control board Problems this kit addresses Erratic or inconsistent heating Heater fails to turn on or cycles off unexpectedly Persistent error codes or unresponsive control panel Poor temperature regulation or delayed response to setpoint changes Electrical malfunctions originating at the control board Before replacing the control board Verify the root cause before installation. Sensors and safety components can be mistaken for a control board failure. Inspect temperature sensor, pressure switch, igniter, wiring, and fuses. Faults in these items can trigger control board failures or mask the true issue. If unsure, consult a qualified technician for diagnosis to avoid unnecessary replacement. Common applications and use scenarios a pool heater that displays persistent error codes and will not maintain set temperature. a failed control board after intermittent shutdowns and unresponsive controls during the heating season. Perform maintenance or upgrade to a more robust control board during preseason service to improve heater reliability. What to expect after installation Faster, more accurate control of burner and fan outputs. Improved electrical stability and reduced risk of repeat failures caused by power irregularities. Restored responsiveness of the control panel and temperature regulation. This 420020007S control board kit provides a durable replacement option for compatible pool and spa heaters, restoring proper electrical control and helping maintain consistent heating performance.