Troubleshooting Compact Furnace Flash Codes (Mr Heater & Heatstar MHU Furnace Repair)

In this video, we walk through the initial startup sequence of a Mr Heater or Heatstar MHU series compact heater with 50,000-120,000 BTU. We explain how the control board signals normal operations (fast flashes), and then move on to show you what the first several flash codes mean and possible fixes for the heater. A 2-flash code means the heater failed to detect a flame. It will run through its sequence 3 times before it times out and you get the 2-flash code. In depth 2 flash code video: https://www.youtube.com/watch?v=_SiCTYVIVo8 A 3 flash code typically means there is a clogged hose/port or defective air switch. A 4-flash code means there is a high heat situation, and you should start by resetting the rollout switch. Chapters: 0:00 Compact Furnace Startup Sequence (Normal Operation) 2:46 Troubleshooting a 2 Flash code 5:27 Troubleshooting a 3 Flash code 7:52 Troubleshooting a 4 Flash code The ignition control board and related items for this furnace can be found here: https://www.allpartsinc.com/60105-ignition-control-board-for-mr-heater-heatstar-enerco.html Disclaimer: Allparts Equipment & Accessories Inc produces videos for educational and informational purposes only. The information provided in this video does not replace professional advice or service. Repeating the work shown in these videos is done at the viewer's own risk. Allparts Equipment & Accessories Inc is not responsible for any damages incurred to the viewer's property (including their home and/or equipment) or health. We strongly recommend hiring a qualified professional when working on your home and/or equipment. It is the viewer's responsibility to follow proper safety protocols when working on their property and to ensure their work complies with all applicable local building codes and regulations. Performing maintenance on machinery, heating systems, and other home equipment is dangerous and should be completed by a qualified professional. Always consult the manufacturer's instruction manual before operating or servicing any equipment. © 2025 Allparts Equipment & Accessories Inc. All rights reserved.