Ruud air conditioner displays E6; unit may not respond properly to thermostat commands or may short-cycle.

Safety first: Turn off power to the indoor unit at the breaker before removing access panels.

• Step 1 – Access evaporator coil: Remove the front panel of the Ruud air handler or furnace coil cabinet. Locate the small sensor clipped to the evaporator coil tubing.
• Step 2 – Check sensor placement: Ensure the thermistor is firmly clipped to the coil and making good contact with the copper tube. Reattach or reposition if loose.
• Step 3 – Inspect wiring: Follow the sensor wires back to the indoor control board. Look for pinched, cut, or chewed wires. Repair with proper splices and electrical tape or heat-shrink tubing.
• Step 4 – Test thermistor: Disconnect the sensor from the board and measure resistance. Compare to Ruud’s chart for the current temperature. Replace if readings are open, shorted, or far off expected values.
• Step 5 – Board evaluation: If a new sensor does not clear E6, the indoor control board may be defective and should be replaced by a technician.