My AC hasnt been used all winter. Now that spring is approaching I turned it on max to give it a test. For about ten seconds it blows cold air when all of a sudden a pretty loud humming noise comes from behind the dash and the air flow cuts to basically 0. Ive tried different speed and airflow settings with the same results. The heat still works fine. Im in the process of changing a faulty engine speed sensor, not sure if that could be part of the issue as Ive read random and strange things can happen without a functioning engine speed sensor. Any ideas?