New Genuine Enerco Mr. Heater High Limit Switch 60015 for Heat Exhanger Combustion Chamber. 

This is a commonly failed part if you are receiving 4 flashes on your Mr. Heater unit. It's likely either this high limit switch, or flame rollout switch. These are Normally Closed switches and will opens on a High Temperature or Over temperature rise.

Compatible with the following and many more models: