Arrived on site to perform Diagnostic on 22 year old carrier system. Homeowner states that system is not heating. System is heat only, does not have AC. cycled system for heat. System starts the heating sequence but then shuts off and locks itself out. Cycled system several different times. On several attempts the inducer fan motor would not kick on even though it was receiving proper voltage and proper command. On other attempts the inducer motor would kick on, but gas valve would not engage despite it having proper voltage and command for it to do so. All safety switches check out as operational and are all opening and closing as they should. On a couple attempts everything kicked on fine and system started heating fine. Inducer fan motor and gas valve are working on and off and should be replaced. When the unit does happen to turn on there is a huge flame rollout at the burner assembly. Inducer draft motor is very rusted out on the side where it connects to the flue pipe that goes a