C 3500 Truck 2WD V8-379 6.2L DSL (1988)
Air Door Actuator / Motor: Customer Interest
A/C - System Locks In Air Conditioning or Heat Mode
Number:
89-326-1A
Section:
1A
Date:
MAY 1991
Corp. Bulletin No.: 161101
Subject:
HVAC SYSTEM LOCKS IN EITHER AIR CONDITIONING OR HEAT MODE
Model and Year:
1988-89 C/K TRUCKS
THIS BULLETIN CANCELS AND SUPERSEDES DEALER SERVICE BULLETIN NO. 89-52-1A, DATED JANUARY 1989 AND 89-325-1A,
DATED APRIL 1991. THE CANCELLED BULLETIN NUMBER HAS BEEN CORRECTED. ALL COPIES OF 89-52-1A AND 89-325-1A
SHOULD BE DISCARDED.
Some 1988 and 1989 C/K trucks may experience a condition where the HVAC system will not come out of either the Heater or the A/C mode when
another mode is requested. This condition is known as "Mode Lockup".
Previously, a jumper harness was released to correct this condition. An improved mode door actuator has been released which no longer requires the use
of the jumper harness and the need to cycle the system into defrost. This "Mode Lockup" is caused by corrosion on the actuator contacts and the new
actuator will eliminate this corrosion. The new actuator will also be about two times faster, as well as quieter.
Figure 1
SERVICE PROCEDURES, MODE ACTUATOR REPLACEMENT (Figure 1)
Remove or Disconnect:
1.
Battery ground cable.
2.
Instrument panel compartment for access.
3.
Electrical connection to the actuator.
4.
Retainer and linkage.
5.
Mode actuator.
Adjust the Mode Actuator:
1.
Install battery ground cable and electrical connection to the actuator.
2.
Turn the ignition key to the run position and let the actuator position itself.
3.
Turn off the ignition key.
4.
Disconnect the electrical connection to the actuator and the battery ground cable.
Install or Connect:
1.
Mode actuator.
2.
Linkage and retainer.
3.
Electrical connection to the actuator.
4.
Instrument panel compartment.
