How to Reset MRCOOL Reverse Cycle Air Conditioner: A Comprehensive Guide

Resetting a MRCOOL reverse cycle air conditioner can be a straightforward process, but it’s essential to understand the proper steps to ensure the system is functioning correctly. This comprehensive guide will walk you through the step-by-step process of resetting your MRCOOL reverse cycle air conditioner, as well as provide advanced troubleshooting tips to help you identify and resolve any underlying issues.

Resetting the MRCOOL Reverse Cycle Air Conditioner

  1. Turn off the Power: Before you begin, it’s crucial to ensure that the power to the air conditioner is turned off at the circuit breaker or fuse box. This step is essential to prevent any electrical hazards and ensure the safety of the reset process.
  2. Locate the Reset Button: The reset button on your MRCOOL reverse cycle air conditioner is typically located on the outdoor unit, near the bottom. It may be a small red button or a recessed button that requires a paperclip or similar object to press.
  3. Press and Hold the Reset Button: Once you’ve located the reset button, press and hold it for a few seconds. You should hear a distinct click as the system resets.
  4. Wait for the System to Restart: After releasing the reset button, the system should start up again on its own. This process may take a few minutes, so be patient and allow the system to complete the restart sequence.
  5. Verify System Operation: Once the system has restarted, check to ensure it is functioning properly. If the system still does not work as expected, you may need to consult the user manual or contact a professional for further assistance.

Advanced Troubleshooting

how to reset MRCOOL reverse cycle air conditioner

If resetting the system does not resolve the issue, there are a few advanced troubleshooting steps you can take to identify and address any underlying problems.

Checking the Reversing Valve Solenoid

One common issue with heat pumps is a malfunctioning reversing valve, which can prevent the system from switching between heating and cooling modes. To troubleshoot this issue, you can check the reversing valve solenoid:

  1. Locate the reversing valve solenoid, which is typically controlled by the defrost board.
  2. Use a multimeter to check for 24 volts of power at the solenoid in heating mode.
  3. If the solenoid is not receiving the correct voltage, it may indicate a problem with the defrost board or wiring.

Checking the Pressure Differential

The reversing valve is controlled by the pilot valve through pressure differential within the system. To check the pressure differential:

  1. Attach pressure gauges to the suction and discharge lines of the reversing valve.
  2. Observe the pressure readings and ensure they are within the manufacturer’s specifications.
  3. If the pressure differential is not correct, it may indicate a problem with the refrigerant charge or a blockage in the system.

Inspecting for Debris

The reversing valve can become stuck due to debris or contaminants in the refrigerant lines. To check for debris:

  1. Visually inspect the reversing valve and the surrounding refrigerant lines for any signs of contamination or blockages.
  2. If you suspect debris is causing the issue, you may need to have the system professionally serviced to clean the lines and components.

If you are not comfortable performing these advanced troubleshooting steps, it is recommended to contact a professional HVAC technician for assistance.


  1. MRCOOL Installation Manual – Heat Pumps:
  2. Heat Pump Reversing Valve Troubleshooting Tips:
  3. MrCool, Why is My Air Conditioner Frozen?: