Samsung mini split error code E221

Common causes

• The outdoor air temperature thermistor has failed (they do drift and fail with age and heat cycling).
• Its plug has worked loose from the control board, or a pin has corroded.
• The sensor lead is chafed, pinched or chewed, giving an intermittent open or short.
• The control board's sensor input has failed (rare compared with the sensor itself).

How to fix it yourself

Work through the checks below first; they resolve most cases. If they do not, the repair itself may need a technician.

1. Reset the system: switch the breaker (or the outdoor disconnect) off, wait a full five minutes so the boards fully discharge, then switch it back on and restart from the remote.
2. If the code comes straight back after a reset, the fault is real and not a glitch.
3. With power off, locate the outdoor air temperature sensor clipped near the coil guard, sensing outside air. Follow its lead back to the board and reseat the plug firmly.
4. Inspect the lead for damage along its whole length, especially where it passes through the chassis.
5. If you have a multimeter, unplug the sensor and measure its resistance. A reading near zero ohms (short) or infinite (open) confirms a bad sensor. Most mini split thermistors read roughly 5 to 20 kΩ at room temperature, so a value in that range with a steady drift as you warm it in your hand means the sensor is fine and the board is the suspect.
6. Replacement thermistors are inexpensive and plug in. Match the part number from the parts list for your model.

Switch off power at the breaker before opening either unit. Capacitors in the outdoor unit hold a charge for several minutes after power is cut.

When to call a technician

Sensor swaps are a doable DIY job on most units. Call a technician if the sensor tests good and the code persists, because that points at the control board.

Which Samsung units show E221

This page applies to Samsung Wind-Free, Quantum, Max Heat and Free Joint Multi units. Samsung's own documentation lists E221 as "Outdoor air temperature sensor fault (open or short circuit)", the same definition used across the Samsung it is built on. If your unit shows a code with a different shape (for example a four-character code, or a plain number), it is from a different table; use the lookup with your exact code.

Where Samsung shows this code

The indoor display shows E followed by three digits (E101, E554). Units without a full display blink the indicator lamps in a pattern the manual decodes; the outdoor board's 7-segment display or LEDs show the same code. E1xx codes are indoor-unit faults, E2xx are communication faults, E4xx are outdoor sensors, protections and inverter faults, and E5xx are outdoor board and refrigerant faults.

Other Samsung codes

Same part of the system as E221:

All Samsung error codes