C-A1 Moderate Moderate DIY

Samsung Microwave C-A1 — Humidity Sensor Open Circuit

Samsung Microwave · Error code C-A1

What C-A1 Means

The control sees an open circuit on the humidity (steam) sensor used for Sensor Cook cycles. Manual time-cook may still work, but Auto/Sensor cycles will not.

Symptoms

  • C-A1 displayed
  • Sensor Cook / Auto Reheat fails immediately
  • Manual cook still works

Common Causes

1
Disconnected sensor harness

Plug came loose between the humidity sensor and the main control.

2
Failed humidity sensor

Sensor element is open.

3
Damaged wiring to the sensor

Heat or rodent damage in the wall of the cavity.

4
Failed main PCB sensor input

Rare; control input circuit damaged.

How to Fix It

  1. Unplug the microwave.
  2. Remove the top/side panel to access the humidity sensor (usually near the cavity vent).
  3. Reseat the harness at both the sensor and the main PCB.
  4. Measure sensor resistance with a multimeter — an open reading confirms a bad sensor.
  5. Replace the humidity sensor with the OEM part.
  6. If wiring and sensor are good, replace the main control board.

Parts You May Need

If diagnosis points to a failed part, these are the common replacements. As an Amazon Associate we earn from qualifying purchases.

Common replacement Samsung microwave humidity sensor View on Amazon→ Common replacement Digital multimeter View on Amazon→

More Samsung Microwave Codes

-dr- -dr- — Door Open (Demo / Reminder) 5E 5E / SE — Touchpad Shorted (Older Spelling) C-21 C-21 — Cavity Over-Temperature C-22 C-22 — Cavity Thermistor Open C-A0 C-A0 — Communication Error Between Boards C-A2 C-A2 — Humidity Sensor Short Circuit

All Samsung codes → All microwave codes →

Verified against manufacturer documentation: samsung.com

Always unplug an appliance before servicing it. This guide is for informational purposes and is not a substitute for a qualified technician.