Customer had no heat coming from kids rooms on second floor, went to air handler to find it blowing cold air but supply line hot return line cold, also found leaking air vent and shut off valve leaking, drained down zone and replaced air vent and shut off valve for kids room air handler, purged system, pumped antifreeze back into system, supply and return pipes got hot, had a105 degrees coming from vents, system operational and working.