Posted by mark on July 03, 04 at 07:22:05:
It just started getting hot here in Texas. I've got a 99 K2500 with the Vortec 7400.
I was parked in front of the local 7-11 on the phone. The engine was on and the AC was running on MAX with the fan on HIGH. After 5-10 minutes of sitting idle the outside temp guage climbed to a false 110 degrees (it was really about 95). All of a sudden the air flow from the main vents started to drop, to virtually a trickle. I switched the AC from MAX to normal/outside air and the air flow picked up again. After a few minutes in non-MAX mode, I heard the blower make some noise like it was self-switching to MAX mode. Then as it did in MAX mode the air flow started to drop.
I shut the car off, got a soda, and ot back on the road with the AC in normal/outside air mode. While driving it never self switched itself to MAX mode. But when trying to switch to MAX mode on the drive home it would exhibit the same behavior of low airflow on high.
So I guess I have 2 questions...
1 -- Is it normal for the AC system to switch itself from normal non-MAX mode to MAX AC mode?
2 -- What would cause the airflow to significantly decrease in MAX mode on any fan setting? I orignally had it on HIGH, but tried all settings and the airflow was significantly reduced. When switch out of MAX airflow was OK until it self-switched to MAX again.
Thanks!