Found 31 year old Trane 80% furnace was not heating the mainfloor of the home. The furnace board was not sending 24 volts to the gas valve and was randomly restarting the sequence of operations. The pressure switch was also randomly dropping out. The furnace is extremely old and maybe a fire and carbon monoxide hazard due to its age and the due to the heat exchangers being in poor condition; combustion analysis can not be done until the furnace operating (homeowner has been advised). The system also needs updated flood protection. The homeowner has been advised about the condition of the furnace and has setup a time with an install supervisor. I emailed repair options.