Amana PTAC or window AC displays E3 and may not cool properly; unit may shut down intermittently.

Safety first: Turn off power at the breaker or unplug the unit. Outdoor sections may expose you to weathered wiring; ensure the area is dry.

Steps to address E3 (outdoor thermistor):

• Access outdoor section: For PTACs, pull the chassis from the wall sleeve. For window units, remove the outer case as per the service manual.
• Locate the outdoor thermistor: It is usually attached to the condenser coil or near the outdoor air intake, with two small-gauge wires leading to the control board.
• Inspect physical condition: Look for cracked sensor body, broken wires, or corrosion at the connector. Clean light corrosion with electrical contact cleaner.
• Test resistance: Disconnect the thermistor and measure resistance with a multimeter. Compare to the Amana temperature/resistance chart. Replace if open, shorted, or out of spec.
• Check wiring harness: Follow the harness back to the control board, ensuring it is not pinched by the cabinet or damaged by vibration.
• Replace defective components: Install a new OEM Amana outdoor thermistor if faulty. If the sensor tests good but E3 remains, suspect a failed main control board.

Because this sensor affects compressor protection, do not bypass it; always repair or replace with the correct part.