A/C System - Humming Noise With Fan On High

Group: 87
Number: 94-11
Date: Dec. 22, 1994

Subject:
A/C System, Humming Noise With Fan On High Speed

Model(s): 90 m.y. 1993 ->

Condition

Slightly deformed or dirty evaporator water drain valve causes whistling or humming noise from fresh air A/C box with fan on high speed.

Service

- Turn fresh air fan on high speed.

Fig. 1 - Evaporator Water Drain Valve:

- Raise vehicle and open drain valve by hand (arrow). If noise goes away then:

- Inspect water drain valve for dirt or other foreign substances. Clean and recheck.

- If valve is free of dirt or any foreign substance and noise is still present after releasing valve, then replace valve.

Note:
Installation tip on replacing the water drain valve:

- Insert a pair of needle nose pliers through the bottom of the drain valve and grab the plastic drain tube with the pliers then slide the valve on to the plastic drain tube.