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ZZDaryl, Chevy Technician
Category: Chevy
Satisfied Customers: 12549
Experience:  28 year experience, Master Mechanic
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2004 chevy silverado .ac has been stuck on defrost since i

Customer Question

2004 chevy silverado .ac has been stuck on defrost since i installed new battery.
Submitted: 8 years ago.
Category: Chevy
Expert:  ZZDaryl replied 8 years ago.

Use the following steps to perform the calibration update:

1. Turn OFF the ignition.

2. Remove the battery positive voltage circuit fuse of the HVAC Control Module(HVAC/ECAS FUSE).

3. Wait 60 seconds.

4. Install the fuse.

5. Turn ON the ignition.

ZZDaryl and 3 other Chevy Specialists are ready to help you
Customer: replied 8 years ago.
I tryed what you suggested.unforgently it didnt work.i have tryed that before .tryed removing battery cables . truck has manual controls which may be problem. looks like im going to bring ot dealer which i was trying to aviod . but thanks for quick reply Customer
Expert:  ZZDaryl replied 8 years ago.

Here is a little different process maybe it will work? If not it will need to be diagnosed.


Alternate Method (w/o Scan Tool)

1. Clear all DTCs.

2. Place the ignition switch to the OFF position.

3. Install the HVAC actuator.

4. Connect all previously disconnected components.

5. Remove the HVAC/ECAS fuse for a minimum of 10 seconds.

6. Install the HVAC/ECAS fuse.

7. Start the vehicle.

8. Wait 40 seconds for the HVAC control module to self-calibrate.

9. Verify that no DTCs have set as current DTCs.