NO DE-FOG FUNCTION (DEFROSTER VALVE DOOR INOP)

SUBJECT: NO DE-FOG FUNCTION OF DEFROSTER VALVE DOOR (SECURE MODULE CASE AND ADJUST SPRING)

VEHICLES AFFECTED: 1992 W-CAR

CONDITION:

--------- The air flow in the defog position may not change properly from defrost to defog, or from heater to defog. The defog position is mid-way between the full defrost and full heat positions. The air flow will be correct when selecting either the defrost or heater position, and defrost operation is not affected.

CAUSE:

----- The defroster valve door may not return to the mid-position (defog). The Heater A/C module upper cover separates from the lower case, causing the torsion spring on the end of the valve door shaft to slip off the end of the shaft, or the torsion spring may slip off the shaft on its own without the case and cover separating.

CORRECTION:

---------- Secure the module cover to the case and adjust the torsion spring so it will stay in position on the valve door shaft. This can be done by using the following part and procedure.

PARTS:

----- QTY. PART NUMBER PART NAME --- ----------- --------- 1 12337820 PLASTIC TIE STRAP 15" Lg.

PROCEDURE

1. Remove the lower R.H. sound insulator.

2. Remove the glove box.

3. Remove the torsion spring from the end of the defroster valve door shaft, see illustration.

4. Check module for separation of the upper case cover from the lower case, in the area indicated in the circle "A" illustration.

5. If the upper cover is separated from the lower case, assemble the case and cover back together.

NOTE: There are two tabs on the bottom of the small dome over the shaft at the right end of the cover. These two tabs should snap into the two slots in the lower case.

Important: Steps 6, 7 and 8 should be done even if the cover and case were not found to be separated.

6. Secure the cover and lower case together with the plastic tie strap, as shown in circle "A" illustration. Cut off the excess leg of the plastic tie strap.

Important: Make sure the plastic tie strap is on the small hood portion of the cover and not on shaft.

7. Bend the leg of the torsion spring, as shown in the illustration.

8. Holding the bent leg of the spring, put coils of the spring on the end of the shaft and engage the other leg in the rear notch of the shaft bracket and then force the bent leg forward to the front side and into the front notch of the shaft bracket. The spring legs should now straddle the black tab below the shaft bracket, as shown in illustration of the assembled spring.

9. Start the engine and check the function of the defroster valve door. Change from Heater to Defroster and Defroster to Heater, and then check the DE-FOG position from both Heater and Defroster positions.

10.Install the glove box.

11.Install the sound insulator.

For vehicles repaired under warranty use: Labour Time 0.6 hours.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.