Begin the system diagnosis by reviewing the system Description and Operation. Refer to Rear Window Defogger Description and Operation . Reviewing the Description and Operation will help you determine the correct symptom diagnostic procedure when a malfunction exists. Reviewing the Description and Operation will also help you determine if the condition described by the customer is normal operation. Refer to Symptoms - Stationary Windows in order to identify the correct procedure for diagnosing the system and where the procedure is located.