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Error code reference

Midea Air Conditioner Error Code Er

Room temperature sensor open circuit or short circuit failure.

Midea codesMidea air conditioner codes

Room temperature sensor open circuit or short circuit failure.

First step from the service manual

Check room temperature sensor wiring and sensor resistance.

The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.

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What Er means on a Midea air conditioner

The Er error code on a Midea air conditioner indicates a failure in the room temperature sensor circuit. This sensor, also called the indoor ambient temperature thermistor, is a negative temperature coefficient (NTC) resistor that continuously reports room temperature to the control board. When the board detects that the resistance reading falls outside the expected range, either dropping near zero (indicating a short circuit) or rising to an open-circuit condition with no continuity, it triggers the Er fault and halts normal operation to prevent incorrect temperature regulation.

The room temperature sensor is typically mounted on the indoor unit's air intake area so it can sample return air temperature accurately. It connects to the main control board via a small wiring harness with a plug-in connector. Failures occur in two forms: an open circuit, where the thermistor wire has broken or the connector has lost contact, resulting in infinite resistance; or a short circuit, where insulation breakdown or connector damage causes resistance to collapse near zero ohms. Either condition produces a signal the control board cannot interpret as a valid temperature reading.

Diagnosis begins by inspecting the sensor wiring harness for visible damage, pinched wires, or loose connectors. The thermistor itself can be tested with a multimeter in resistance mode. A functioning NTC thermistor will show a resistance value that decreases as temperature increases. If the connector and wiring are intact but the resistance reading is open or near zero, the sensor requires replacement. If wiring shows damage or corrosion at the connector pins, the harness may need repair or replacement as well.

Source: manufacturer service documentation.

Common causes of Er

  1. 01

    Failed room temperature thermistor

    Part replacement

    The NTC thermistor itself has degraded internally, resulting in an open circuit (infinite resistance) or short circuit (near-zero resistance) that the control board cannot interpret as a valid temperature. Testing the sensor with a multimeter will confirm a reading that is out of the normal operating range.

  2. 02

    Loose or disconnected sensor connector

    Wiring / connection

    The plug connecting the sensor wiring harness to the control board may have vibrated loose or was never fully seated, causing an intermittent or permanent open circuit. Inspect the connector at both the sensor end and the board end for proper engagement.

  3. 03

    Damaged sensor wiring harness

    Part replacement

    Wires in the harness can become pinched, cut, or chafed against cabinet edges or other components, breaking continuity or causing a short to ground. A visual inspection of the full wire run and a continuity test on each wire will identify the fault location.

  4. 04

    Corroded or contaminated connector pins

    Wiring / connection

    Moisture or dust buildup on the connector pins can increase resistance enough to simulate an open circuit condition. Cleaning the pins carefully and reseating the connector may resolve the fault without replacing the sensor.

  5. 05

    Control board input circuit fault

    Part replacement

    If the sensor and wiring both test correctly, the sensor input circuit on the main control board may have failed, causing it to misread or not detect the sensor signal. This is the least common cause and is confirmed only after ruling out the sensor and wiring.

See the test procedure for each cause

Frequently asked questions about Er

What does Er mean on a Midea air_conditioner?
The Er code on a Midea air conditioner indicates a room temperature sensor open circuit or short circuit failure. The indoor ambient temperature thermistor is sending a signal that the control board cannot recognize as a valid temperature reading. The unit will not operate normally until the fault is diagnosed and corrected.
Can I fix the Er error on my Midea air conditioner myself?
A knowledgeable DIYer can start by checking that the sensor connector is firmly seated and that the wiring has no visible damage. Testing the thermistor with a multimeter in resistance mode will confirm whether the sensor itself has failed. If the sensor reads open or shorted, replacing it is a relatively straightforward repair, though working inside the unit requires disconnecting power first.
Is it safe to run my Midea air conditioner with the Er error showing?
The unit will typically stop normal operation when the Er code appears, which is a protective response to prevent incorrect temperature control. Attempting to force the unit to run without a functioning room temperature sensor can result in improper cooling cycles or compressor behavior. It is best to resolve the fault before resuming regular use.
How much does it cost to repair the Er error on a Midea air conditioner?
If only the room temperature thermistor needs replacement, parts typically range from a few dollars to around $20 to $40 depending on the model. If a technician performs the repair, total costs including labor will generally range from $75 to $200. Control board replacement, if required, is more expensive and could bring the total to $150 to $400 or more.
Will resetting my Midea air conditioner clear the Er error code?
Powering the unit off and back on may temporarily clear the display, but the Er code will return if the underlying sensor or wiring fault has not been corrected. A reset does not repair a failed thermistor or broken wire. The fault must be physically diagnosed and repaired for the error to stay cleared.

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