Raypak heat pump or controller displays Er1; unit will not operate.

Safety first: Turn off power before accessing sensors or the control board.

• Locate inlet sensor: Identify the inlet water temperature sensor on the Raypak manifold. Ensure it is properly seated and not physically damaged.
• Check wiring: Inspect the sensor cable for cuts, abrasions, or rodent damage. Reseat the connector at the control board.
• Measure resistance: Compare the sensor resistance to the Raypak temperature/resistance chart. Replace the sensor if readings are out of range.
• Replace sensor if needed: Shut off water, remove the sensor from its well or port, install the new Raypak sensor with proper sealing, and test for leaks before restoring power.