My 2004 chevy silverado has air conditioning problem. sometimes it blows out cool air and sometimes it won't work.

start with using a meter to test for power start from fan back to switches need to check harness and connectors

you can try to diagnose,Multi-Diag Access J2534 has the function for air condition, such as Diagnosis of cooling electronic,
Reading settings cooling circuit,Test servo actuators
http://www.allobd2.com/wholesale/[email protected]

If it has dual zone temp. control it is most likely the heater control panel.

Had exact same problem with my 2006 Chevy Silverado 1500. Would blow hot air thru drivers vents only and sometimes if I turned truck off and restarted would blow air conditioner for a bit. Rec'd recall letter from Chevrolet in January for this problem.

#46-12-03: AIR CONDITIONER BLOWS WARM AIR (REPLACE A/C DELAY RELAY) - (Apr 7, 1994) REVISION: 04/14/94
THIS BULLETIN IS BEING REVISED TO CORRECT THE TRANSMISSION LISTED IN THE MODELS. ----------------------------------------------------------------------
SUBJECT: AIR CONDITIONER BLOWS WARM AIR (REPLACE A/C DELAY RELAY)
MODELS: 1994 CHEVROLET AND GMC TRUCK S/T PICKUP WITH 4.3 ENGINE (VIN Z - RPO LB4), 4L60E TRANSMISSION (M30) AND AIR CONDITIONER/MANUAL CONTROLS (C60); OR 4.3 ENGINE (VIN W - RPO L35) AND A/C (C60)
BUILT BEFORE THE FOLLOWING VIN BREAKPOINTS:
PLANT DIVISION VIN LINDEN GMC RK501034 SHREVEPORT GMC R8501199 SHREVEPORT CHEVROLET R8105893 LINDEN CHEVROLET RK103097
CONDITION:
SOME OWNERS MAY EXPERIENCE A CONDITION WHERE THE AIR CONDITIONER IS TURNED ON AND DELIVERS ONLY WARM AIR.
CAUSE:
THE AIR CONDITIONER COMPRESSOR MAY DELAY LONGER THAN THE "ORIGINAL DESIGN" INTENDED 12 SECONDS, OR MAY NOT ENGAGE, DUE TO THE POSSIBLE MALFUNCTION OF THE COMPRESSOR DELAY RELAY.
CORRECTION:
TRUCKS BUILT BEFORE THE VIN BREAKPOINTS LISTED ABOVE MAY NEED A NEW AIR CONDITIONER DELAY RELAY. REPLACE ONLY WITH 15990540 AIR CONDITIONER COMPRESSOR DELAY RELAY. SPECIFIED PROCEDURE IN SERVICE MANUAL NATP 9429, PAGE 1B-59. TEST AIR CONDITIONER OPERATION FOR DELIVERY OF COOL AIR.
NOTE:TO TEST FOR PROPER OPERATION, PUT THE A/C CONTROL ON THE "OFF" POSITION, START THE ENGINE, THEN PLACE THE A/C CONTROL IN THE "ON" POSITION. THIS SEQUENCE WILL PROVIDE IMMEDIATE ENGAGEMENT OF THE AIR CONDITIONER COMPRESSOR. WHEN THE ENGINE IS STARTED WITH THE A/C CONTROL ALREADY "ON", THERE WILL BE A NORMAL 15.0 SECOND DELAY FOR THE AIR CONDITIONER TO ENGAGE.
SERVICE PARTS INFORMATION:
P/N DESCRIPTION QTY
15990540 A/C COMPRESSOR DELAY RELAY 1
PARTS ARE CURRENTLY AVAILABLE FROM GMSPO.

2004 chevy Avalanches air conditioner blows hot air, can the actuator be forced to keep it blowing cold air instead of hot air all the time.

I have the same problem exactly, if i turn off the ignition and then turn it back on it begins blowing cold air again. I would like to know what the problen is as it sounds like it is not unique to just my vehicle.

first thing is insure that u have the temp control turned all the way to coldest and the a/c button is pushed in (if u have one) if that doesnt work then(i hestitate to say this) have him check the fuses again. if he finds no blown fuses and this includes the ones in the box under the hood, then its off to the repair shop u go for the big rip off.

check the freon level

whenb this happens you have most likely lost the vacum to the control and so the unit goes iunto defrost as a safety feature you may want to chk for vacum