A/C Plenum - High Pitched Whistling Noise

Article No.
01-15-4

08/06/01

^ CLIMATE CONTROL - HIGH PITCHED WHISTLE
NOISE FROM THE A/C PLENUM AREA - HIGHWAY
SPEEDS ONLY - VEHICLES BUILT 04/04/2001
THROUGH 05/17/2001

^ NOISE - HIGH PITCHED WHISTLE NOISE FROM
THE A/C PLENUM AREA - HIGHWAY SPEEDS
ONLY - VEHICLES BUILT 04/04/2001 THROUGH
05/17/2001

FORD:
2001 CROWN VICTORIA

MERCURY:
2001 GRAND MARQUIS

ISSUE

Some vehicles may exhibit a high pitched whistle noise from the A/C plenum area while driving at highway speeds greater than 88 km/h (55 mph) with the A/C system in the Oft or Max A/C settings. This may be caused by the air flow over the water drain flap door on the air inlet duct.

ACTION

There are 4 molded vertical ribs in the housing behind the A/C drain flap. Cut a notch in rib 3 as shown. Refer to the following Service Procedure for details.

SERVICE PROCEDURE

When the air inlet duct door is in the MAX A/C or OFF position, ram air on the fresh air side of the duct is exiting through the drain at the bottom of the duct and then re-entering the drain on the recirculation side of the drain. The air is flowing behind the rubber drain flap and over a molded plastic rib in the housing. The air flow through this narrow gap is generating the whistle noise.

1. Verify the condition. Drive the vehicle on a highway at a speed greater than 88 km/h (55 mph). To ensure that the whistle sound is being generated by the drain flap, turn the A/C system to Off or Max A/C. You should be able to hear the noise. Next change the A/C setting to Normal A/C, the whistle should go away. This will happen on both Manual and EATC equipped vehicles. Keep the fan selling at its lowest so that you can listen for the whistle.

NOTE
IF THE WHISTLE COMES AND GOES AS YOU CHANGE BETWEEN MAX A/C (OR OFF) AND NORMAL A/C, THEN THE DRAIN FLAP IS THE SOURCE FOR THE NOISE.

2. Raise vehicle on hoist.

3. Remove right front wheel.





4. Loosen and remove rear fender apron screw (Figure 1).





5. Peel back fender apron to gain access to inlet air duct drain flap (Figure 2).

6. Lift A/C drain flap, 4 molded vertical ribs in the housing should be visible.





7. Cut a notch in rib number 3 (Figure 3). Use a pair of side cutters to cut the notch.

8. Place fender apron back in place.

9. Re-secure fender apron screw (11.5 +/- 2.5 N.m).

10. Re-secure wheel to vehicle (115 - 142 N.m).

11. Lower vehicle from hoist.

WARRANTY STATUS: Eligible Under The Provisions Of Bumper To Bumper Warranty Coverage

OPERATION DESCRIPTION TIME

011504A Cut Notch In Housing 0.6 Hr.

DEALER CODING
CONDITION
BASIC PART NO. CODE
19C590 42

OASIS CODES: 208000, 702000, 702100, 702300