A/C - Loss of Heating/Cooling Control

91chevy07

Number: 91-200-1A


Section: 1A


Date: February 1991


Corporate Bulletin No.: 131201


Subject: LOSS OF HEATING OR COOLING CONTROL


Model and Year: 1991 CORVETTE WITH 5.7L ENGINE


Condition: On some vehicles the temperature of air coming from the HVAC system, with C68 option, cannot be changed. A code 01 or 02 may also be set in the HVAC control head. The "auto" blower may read "0" speed.


Cause: The air mix door of the HVAC system will not move out of the full hot or full cold position, causing loss of heating or cooling control, because the mix motor has not recalibrated itself.


Correction: This condition may be caused by wiring disconnects, air mix door motor condition, Freon loss, or related A/C system conditions. If normal diagnostic procedures do not correct this condition, a revised A/C programmer is available. This change was made in production with VIN M5101083 (L98) and M5800130 (LT5).

Part Number Engine

16140190 L98 (VIN Code 8)

16151009 LT5 (VIN Code J)
IMPORTANT: THE 1990 AND 1991 C68 PROGRAMMERS ARE NOT INTERCHANGEABLE.

Parts are currently available from GMSPO.

Use the procedure in Section 1C1 of the 1991 Service Manual to replace the programmer.

NOTICE: WHILE WORKING ON THE HVAC SYSTEM, DO NOT RUN THE AIR MIX DOOR MOTOR WHEN IT IS REMOVED FROM THE HEATER CASE. THIS WILL DAMAGE THE MOTOR.


Warranty information: Use labor operation number D0780.


Use applicable Labor Time Guide for labor hours.