Ruud air conditioner (heat pump) displays H1; the unit may stay in defrost too long or not defrost properly.

Safety first: Disconnect power at the outdoor disconnect before working on sensors or control boards.

• Step 1 – Locate the defrost sensor: Find the thermistor clipped to the outdoor coil tubing, usually near the bottom of the coil.
• Step 2 – Check attachment: Ensure the sensor is firmly clipped and making good contact with the copper tube. Reattach it if loose.
• Step 3 – Inspect wiring: Follow the sensor wires back to the defrost control board. Repair any damaged insulation or broken conductors.
• Step 4 – Measure resistance: Disconnect the sensor and test it with a multimeter. Compare the reading to Ruud’s temperature/resistance chart. Replace the sensor if it is out of range.
• Step 5 – Replace the defrost control board if needed: If a new sensor does not resolve H1, the defrost control board may be faulty and should be replaced.