Talk to the dealer, there is an updated part number for a special low pressure switch...
89040362 Low pressure cycling switch..Make sure they used that number for the part...
I also found this info... but it's probably the switch again.. somethings wrong with a lot of the first design switches.... Bobo
HVAC System Inoperative for a Drive Cycle, Poor HVAC System Performance in High Ambient Temperatures (Update HVAC Control Module Software) #02-01-39-005 - (09/23/2002) HVAC System Inoperative For A Drive Cycle, Poor HVAC System Performance In High Ambient Temperatures (Update HVAC Control Module Software)
2002-2003 Chevrolet TrailBlazer, TrailBlazer EXT2002-2003 GMC Envoy, Envoy XL
2002-2003 Oldsmobile BravadaCondition Some customers may comment about no cold air from the heating, ventilation and air conditioning (HVAC) system during a drive cycle. This concern may occur at any time during the drive cycle and at any temperature setting. The HVAC system operation returns to normal after the vehicle has been keyed to off and restarted. This concern is intermittent and most likely to occur on hot days. This concern may be found on vehicles equipped with manual (CJ2) and automatic (CJ3) HVAC systems. Other customers may comment about poor HVAC system performance in high ambient temperature conditions. This concern may be present in automatic (CJ2) HVAC systems only. An HVAC control module software update was put into all production vehicles beginning in September
2002. Vehicles built in September 2002 and earlier may need this software update.Correction Update the HVAC control module using software available through GM Access beginning September 9, 2002. The update will be fully available October 7,
2002 to all dealers on TIS 2000 CD version 10. This software update addresses both the intermittent no cooling and the poor performance concerns. If the software update does not correct the concerns, perform the HVAC Diagnostic System Check and repair as necessary. If the HVAC control module is replaced with a part from GMSPO, make sure the module has the latest software update. The module may need to be updated even though it is a new part.
Yeah, I get the same thing in my 2003 LT 4x4. After about a month during a hot spell here (>100F) it started blowing nothing but hot air with a funky/humid smell. That went on for about 2 weeks, then it started working fine again and has been OK for about a month. I want to take it in to get checked out but have precious little free time and little hope of them rooting out the problem if isn't acting up.
MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.