What causes Midea Mini Split E1?

A loose, miswired or damaged connection in the cable between the indoor and outdoor units, especially the S (signal) and N terminals. Midea's flowchart checks the indoor and outdoor wiring connections before any parts. Power to the outdoor unit is off or interrupted, so it can't answer the indoor unit (for example a tripped outdoor breaker or disconnect). A faulty reactor in the outdoor unit. Midea lists the reactor as a part to prepare and checks it when the outdoor wiring is fine. A faulty outdoor control board (PCB). A faulty indoor control board (PCB). Midea's voltage test is how a technician tells the indoor and outdoor boards apart.

How do I fix Midea Mini Split E1?

Do Midea's first step: turn the system off, wait 2 minutes, then restart it. If E1 doesn't come back, the unit is operating normally. Check that the outdoor unit actually has power. Look for a tripped breaker in your panel and make sure the outdoor disconnect switch is on. Walk the line set and the cable between the units from the outside. Note any cut, chewed, crushed or water-soaked cable, or anything disturbed by recent work, and tell your technician. If E1 started right after installation or after the unit was moved, call the installer first, since the interconnecting wiring is part of their work and may be covered by their workmanship warranty. Don't open the indoor or outdoor unit's electrical covers. These are high-voltage, inverter units that store charge even after power is off.

When should I call a pro for Midea Mini Split E1?

E1 returns after the 2-minute restart. A technician measures the DC voltage between the S and N terminals at the outdoor unit (red lead on S, black on N), which is Midea's next step. The voltage swings back and forth between positive and negative values. Midea says that is normal communication, so the technician checks the outdoor wiring, then the reactor (replace it if faulty), then replaces the outdoor board, and the indoor board only if the error remains. The voltage stays positive the whole time. Midea's remarks say this points to an outdoor unit malfunction. The voltage sits at a fixed value. Midea says this points to the indoor unit, so the technician checks the indoor wiring connections and then replaces the indoor board, followed by the outdoor board if E1 still isn't resolved.

Code: E1🔧 Midea Mini Split

Midea Mini Split Error Code E1: Indoor and Outdoor Unit Communication Error (Meaning, Causes, Fixes)

Q: What does Midea Mini Split E1 mean?

E1 on a Midea mini split means the indoor unit has stopped hearing back from the outdoor unit. Midea's service manuals call it an indoor and outdoor unit communication error. The usual suspects are the wiring between the two units, the outdoor board or its reactor, or the indoor board, and Midea's first step is simply to power the system off and restart it after 2 minutes. Midea's Oasis Plus 3D Inverter service manual lists E1 as "Indoor / outdoor units communication error" and sets it when "the indoor unit has not received feedback from the outdoor unit for 150 seconds, four consecutive times." Older Midea manuals, such as the MSMBB-12CRDN1 service manual, use the same rule with a 110-second window. The indoor and outdoor units talk over the S (signal) wire in the interconnecting cable, so anything that breaks that conversation, from a loose terminal to a failed board, can trigger E1. On Midea cassette, duct and other units with indicator lamps instead of a display, the error tables show this fault as the timer lamp off with the operation lamp flashing twice. Some newer Midea documents label the same communication fault EL 01.

Reviewed 2026-10-24 · Based on 4 manufacturer & service sources

What the code means

Midea's Oasis Plus 3D Inverter service manual lists E1 as "Indoor / outdoor units communication error" and sets it when "the indoor unit has not received feedback from the outdoor unit for 150 seconds, four consecutive times." Older Midea manuals, such as the MSMBB-12CRDN1 service manual, use the same rule with a 110-second window. The indoor and outdoor units talk over the S (signal) wire in the interconnecting cable, so anything that breaks that conversation, from a loose terminal to a failed board, can trigger E1. On Midea cassette, duct and other units with indicator lamps instead of a display, the error tables show this fault as the timer lamp off with the operation lamp flashing twice. Some newer Midea documents label the same communication fault EL 01.

Likely causes

A loose, miswired or damaged connection in the cable between the indoor and outdoor units, especially the S (signal) and N terminals. Midea's flowchart checks the indoor and outdoor wiring connections before any parts.
Power to the outdoor unit is off or interrupted, so it can't answer the indoor unit (for example a tripped outdoor breaker or disconnect).
A faulty reactor in the outdoor unit. Midea lists the reactor as a part to prepare and checks it when the outdoor wiring is fine.
A faulty outdoor control board (PCB).
A faulty indoor control board (PCB). Midea's voltage test is how a technician tells the indoor and outdoor boards apart.

Safe DIY checks

⚠ Before you start

The cable between a mini split's indoor and outdoor units carries line voltage, and the communication terminals share that terminal block, so turn off the breaker before touching any wiring and leave voltage testing to a licensed HVAC technician. Inverter outdoor units store a dangerous charge in their capacitors even after the power is off, and many newer Midea units use R32 refrigerant, which is mildly flammable.

Do Midea's first step: turn the system off, wait 2 minutes, then restart it. If E1 doesn't come back, the unit is operating normally.
Check that the outdoor unit actually has power. Look for a tripped breaker in your panel and make sure the outdoor disconnect switch is on.
Walk the line set and the cable between the units from the outside. Note any cut, chewed, crushed or water-soaked cable, or anything disturbed by recent work, and tell your technician.
If E1 started right after installation or after the unit was moved, call the installer first, since the interconnecting wiring is part of their work and may be covered by their workmanship warranty.
Don't open the indoor or outdoor unit's electrical covers. These are high-voltage, inverter units that store charge even after power is off.

🛠 When to call a pro

E1 returns after the 2-minute restart. A technician measures the DC voltage between the S and N terminals at the outdoor unit (red lead on S, black on N), which is Midea's next step.
The voltage swings back and forth between positive and negative values. Midea says that is normal communication, so the technician checks the outdoor wiring, then the reactor (replace it if faulty), then replaces the outdoor board, and the indoor board only if the error remains.
The voltage stays positive the whole time. Midea's remarks say this points to an outdoor unit malfunction.
The voltage sits at a fixed value. Midea says this points to the indoor unit, so the technician checks the indoor wiring connections and then replaces the indoor board, followed by the outdoor board if E1 still isn't resolved.

Parts that commonly fix it

Always match the part number to your exact model.

⚙

Outdoor control board

Midea's flowchart replaces this when the outdoor wiring and reactor check out; match the outdoor unit model number before ordering.

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⚙

Indoor control board

Only after the voltage test points to the indoor unit; match the indoor unit model number.

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⚙

Multimeter

Used for Midea's S-to-N voltage test, by a qualified technician.

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Sources

Last reviewed 2026-10-24. Always confirm against the manual for your exact model number.

Midea Mini Split Error Code E1: Indoor and Outdoor Unit Communication Error (Meaning, Causes, Fixes)

What the code means

Likely causes

Safe DIY checks

🛠 When to call a pro

Parts that commonly fix it

Outdoor control board

Indoor control board

Multimeter

Related codes

Sources