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.

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-ign...