Indoor and Outdoor Unit Communication Error

What it means

This code appears on Samsung inverter split wall units such as WindFree and Digital Inverter. It means the indoor unit did not get a valid reply from the outdoor unit within the set time. The compressor stops and there is no cooling until communication returns, although the indoor fan may keep running. The same code can mean something else on other brands.

Models covered: Samsung inverter split air conditioners (e.g. WindFree and Digital Inverter wall units) that show three-digit E codes on the display.

Related codes: E466E464E458E121

Symptoms4

• E101 appears a few minutes after switching on.
• The outdoor unit never starts, or runs and then stops suddenly.
• The fault may begin after a power cut, a lightning strike or renovation work.
• The code comes and goes on some days and not others.

Possible causes6

• Loose, corroded or wrongly ordered terminals on the interconnecting cable.
• No power at the outdoor unit because a breaker is off or a fuse on its board has blown.
• Damaged, cut or undersized interconnecting cable, or a poor joint hidden in the wall.
• Outdoor PCB fault, sometimes caused by a failed IPM or power supply circuit.
• Faulty communication circuit on the indoor PCB.
• Severe voltage swings or electrical noise from nearby equipment.

How to diagnose6

1. Switch off the breaker for at least five minutes and restart; make sure the outdoor unit breaker is on if it is separate.
2. Watch the outdoor unit after start-up: does the fan start or can you hear it run? No movement usually means it has no power.
3. A technician checks both terminal blocks for tight connections and correct order per the Samsung diagram.
4. Check continuity and insulation of the cable wires and look for any hidden mid-run joint.
5. Confirm power reaches the outdoor unit and check its board fuse and indicators; if the fuse has blown, find the cause before replacing it.
6. If power and cable are good, determine which board has failed.

How to fix6

1. Tighten, clean and correct the order of the terminals.
2. Replace a damaged cable with a single, correctly sized run without joints.
3. Restore power to the outdoor unit after finding why the breaker tripped or the fuse blew.
4. Fit a voltage protector if the local supply fluctuates.
5. Replace the failed PCB (the outdoor one in most cases).
6. Run the unit long enough and confirm the outdoor unit keeps running without the code.

The cost is low for a terminal or cable fault and reaches the top of the range when the outdoor inverter PCB has to be replaced.

Prices are rough estimates including the part and the technician’s fee, and vary with brand, model and part source.
Prices last updated: September 2026

Frequently asked questions