Preformed heating maintenance on single system gas. All electrical company safeties tested within manufacturer specifications. When we checked for gas leaks we found a leak at the top burner indicating a bad gas valve. Temp being supplied to the house was 121 and return was 79. Client had filter for us to change. Client has parts and labor for us to change out the gas valve. Unit was back to cooling upon departure We preformed dryer vent cleaning. Presented before and after pictures to client. Changed gas valve under warranty.