0748 Heat exchanger heat flow
0749 Draft hoods
0750 House air flow
0751 Exhaust breech through cold air return
0752 Heat pump coil upstream of heat exchanger
0753 Downflow and upflow furnaces
0754 Horizontal gas-fired furnace
0755 Fan cover missing
0756 Furnace covers |  0757 Draft hoods
0758 Furnace clearances
0759 Fan switch
0760 Fan/limit switch
0761 Fan/limit switch set wrong or defective
0762 Thermostat - bi-metallic (mercury bulb)
0763 Themostat - bi-metallic (snap-action)
0764 Variable thermostat anticipator
0765 Thermostat must be level |
