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Error code reference

Mitsubishi Air Conditioner Error Code MT2

Maintenance signal output 2

Mitsubishi codesMitsubishi air conditioner codes

Maintenance signal output 2 - inverter cumulative energization time reached or exceeded Pr.687 set value.

First step from the service manual

Take appropriate countermeasures according to the purpose of maintenance timer setting.

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

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What MT2 means on a Mitsubishi air conditioner

The MT2 error code on a Mitsubishi air conditioner is a maintenance signal output, not a fault or failure condition. It indicates that the inverter's cumulative energization time has reached or exceeded the threshold value programmed into parameter Pr.687. This parameter allows technicians or facility managers to set a specific operating hour target, after which the system flags the MT2 signal to prompt scheduled maintenance activity. The inverter tracks total powered-on hours continuously, and once that count meets or surpasses the Pr.687 value, the maintenance signal is triggered.

This code is a scheduled maintenance reminder built into the inverter control system. The purpose of Pr.687 is to allow customized maintenance intervals tailored to the installation environment, usage intensity, or service contract requirements. Because different applications may demand different service frequencies, the parameter is user-configurable. Common maintenance actions tied to this timer include filter cleaning, refrigerant checks, electrical connection inspections, and lubrication of moving components such as fan motors.

Addressing MT2 requires taking the appropriate countermeasures based on why the maintenance timer was originally set. Once the required maintenance tasks are completed, the cumulative energization timer typically needs to be reset and Pr.687 reviewed or reprogrammed to establish the next maintenance interval. Ignoring this signal will not immediately cause equipment failure, but the system is designed to alert service personnel that the predefined service interval has elapsed and attention is due.

Source: manufacturer service documentation.

Common causes of MT2

  1. 01

    Cumulative inverter run hours reached preset limit

    Wiring / connection

    The most direct cause is that the inverter has accumulated operating hours equal to or greater than the value set in parameter Pr.687. This is the intended trigger for the MT2 signal and confirms that the maintenance interval has been reached.

  2. 02

    Maintenance timer not reset after previous service

    Wiring / connection

    If the cumulative energization timer was not reset following the last scheduled maintenance visit, the timer continues accumulating and can trigger MT2 again sooner than expected. Verify the timer was properly cleared after the prior service.

  3. 03

    Pr.687 set to a lower value than intended

    Wiring / connection

    If the maintenance interval parameter Pr.687 was programmed with a lower hour value than appropriate for the application, the MT2 signal will trigger more frequently than planned. Review and adjust the parameter to match the intended service schedule.

  4. 04

    High-demand operating environment shortening intervals

    Wiring / connection

    Units operating in dusty, humid, or high-load environments accumulate run hours faster and may require more frequent maintenance than the original Pr.687 setting anticipated. Consider adjusting the parameter to reflect actual usage conditions.

  5. 05

    Scheduled maintenance tasks not yet completed

    Wiring / connection

    The MT2 signal may persist if maintenance activities such as filter cleaning, refrigerant inspection, or electrical checks have not been performed since the timer triggered. Complete all required service tasks before resetting the timer.

See the test procedure for each cause

Frequently asked questions about MT2

What does MT2 mean on a Mitsubishi air_conditioner?
MT2 is a maintenance signal output indicating that the inverter's cumulative energization time has reached or exceeded the threshold set in parameter Pr.687. It is a scheduled maintenance reminder, not a system fault or component failure. The code is designed to alert technicians that a preset operating hour interval has elapsed and that service is due. Once appropriate maintenance is performed and the timer is reset, the signal clears.
How do I fix the MT2 error on my Mitsubishi air conditioner?
Fixing MT2 involves completing the maintenance tasks that correspond to the purpose for which the timer was originally configured, such as filter cleaning, refrigerant checks, or electrical inspections. After completing the required service, the cumulative energization timer must be reset and parameter Pr.687 should be reviewed to confirm the next interval is set correctly. A qualified technician with access to the inverter parameter settings should perform this process.
Is it safe to keep running my Mitsubishi air conditioner when MT2 is showing?
The MT2 signal is a maintenance reminder and does not indicate an active component failure, so the unit will typically continue to operate. However, running the system beyond the maintenance interval without servicing it can lead to reduced efficiency or undetected wear. It is advisable to schedule a service visit promptly to address whatever maintenance the timer was set to flag.
Will resetting the unit clear the MT2 error code?
A simple power cycle or reset of the unit will generally not clear MT2 because the cumulative energization timer in the inverter continues to reflect that the Pr.687 threshold has been met. Clearing the code requires resetting the maintenance timer through the inverter parameter settings, typically after completing the required maintenance work. Resetting without performing the maintenance is not recommended.
How much does it cost to service a Mitsubishi air conditioner after an MT2 alert?
Service costs following an MT2 alert vary depending on what maintenance tasks are required and local labor rates, but a routine maintenance visit typically ranges from $80 to $250. If the service reveals additional issues such as refrigerant recharge needs or component wear, costs can range higher, potentially from $150 to $500 or more depending on parts and labor involved. Getting a detailed estimate from a certified technician before work begins is recommended.

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