Begin the system diagnosis by reviewing the Air Delivery Description and Operation and the Air Temperature Description and Operation . Reviewing the Description and Operation information will help you determine the correct symptom diagnostic procedure when a malfunction exists. Reviewing the Description and Operation information will also help you determine if the condition described by the customer is normal operation. Refer to Symptoms - HVAC Systems - Manual in order to identify the correct procedure for diagnosing the system and where the procedure is located.