1990 Corvette: Service Bulletin: Loss of Heating or Cooling Control

Subject: Loss of Heating or Cooling Control - New Programmer
Model and Year: 1990 CORVETTE
Source: Chevrolet Service Bulletin
Bulletin Number: 90-378-1A - (10/25/1990)

TO: ALL CHEVROLET DEALERS

Condition:

The customer may comment on a loss of heating or cooling control. The temperature of air coming from the HVAC system cannot be changed. A code 01 or 02 may also be set in the HVAC control head. The "auto" blower may read "O" 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 failed to recalibrate itself.

Correction:

This condition may be caused by wiring disconnects, air mix door motor condition, Freon loss, or related A/C system problems. If normal diagnostic procedures do not correct this condition, a revised A/C programmer is available.

Part Number Engine
----------- ---------------
16155285 L98 (VIN Code 8)
16155286 LT5 (VIN Code J)

Use the procedure in Section 1C1 of the 1990 Service Manual to replace the programmer.

If a DELCO-LOC 11 security code has been programmed originally into the radio by the customer, the radio may display "LOC" when the battery cable is disconnected. If this condition occurs, the customer will have to re-enter his/her security code to turn on the radio. Refer to Section 9A in the Service Manual for further information on this procedure.

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.

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.