A/C Blower Fan - Runs Continuously With Ignition Off

File In Section: 1 - HVAC

Bulletin No.: 86-12-08

Date: June, 1998

Subject:
HVAC Blower Fan Runs Continuously with Ignition Off (Replace A/C Control Assembly)

Models:
1998 Chevrolet and GMC S/T Models
1998 Oldsmobile Bravada
with RPO C68

Condition

Some owners may comment that the blower fan keeps running after the ignition is turned OFF.

Cause

If the ignition key is turned off within a very short time window, the blower speed output timer may not reset during the power down sequence. When this occurs, the control assembly will continue to output a 8hz signal to the pulse width modulation (PWM) blower driver.

The PWM blower driver is designed to operate at between 30-50hz, but may operate at a frequency as low as 8hz. If the key is turned off during this very short time window, and a signal of 8hz is triggered, the fan will run until the battery is dead or until the ignition key is cycled on and off.

Correction

Replace the A/C control assembly using the part number(s) listed. Use the Service Procedure in Section 1B of the Service Manual.





Parts Information

Parts are currently available from GMSPO.

Warranty Information

For vehicles repaired under warranty, use:

Labor Operation Description Labor Time
D0362 Control Assembly Labor Operation
(A/C) - Replace Time

Important:
Labor operation is coded to base vehicle coverage in the warranty system.