Loren Cook 778531 Belt Tensioner 322838 753 The Laars Heating Systems A2123404 The Laars Heating Systems A2123404 is a professional grade 1 3 HP pump motor and base assembly engineered for high demand hydronic circulation in specific Laars boiler and volume water heater configurations When you are troubleshooting short cycling or "pressure switch open" fault codes you must flip the internal spring "tail" and snap the directional arrow into the opposite position so it points toward the belt being tensioned this automatic tensioner utilizes a internal spring mechanism to eliminate belt slippage and reduce vibration during startup and continuous operation