Amana central AC control shows F4; outdoor unit may not run even though thermostat calls for cooling.

Safety first: Shut off power to the outdoor unit at the disconnect before opening the control panel.

Steps to address F4 (outdoor temperature sensor):

• Locate sensor: Open the outdoor unit control panel. The ambient sensor is typically a small thermistor mounted near the coil or on the control panel, with two wires to the board.
• Inspect condition: Check for cracked casing, corrosion, or rodent damage to the wires. Dry any moisture and clean light corrosion.
• Test resistance: Disconnect the sensor and measure resistance. Compare to the Amana temperature/resistance chart. Replace if readings are open, shorted, or out of range.
• Check board input: If the sensor tests good, the control board may not be reading it correctly. Replace the board if F4 persists with a known-good sensor.

Mount the replacement sensor in the same location to ensure accurate outdoor temperature readings for system protection and staging.