Ventilation

2000LTZ71 · April 18, 2002

I've noticed the last few days that even when I have the fan turned off if I put the temp control as cold as possible and have the vent selector on dash vents that I get a good flow of very cold air, even colder then what the air temp is out side. The air conditioning button is not lit up so I'm assuming it's not on. has anyone else noticed this happen to them. Is this right? shouldn't there be no air coming through with the fan off?

Markeaux · April 18, 2002

If Recirc is on and Vent selected then the a/c compressor comes on yet the a/c light does not illuminate ... something about the windshield/windows could fog w/o the drying of the air so it's a safety feature

2000LTZ71 · April 19, 2002

How can you tell if the Recirc is on? when the fan switch is off neither the recirc or the direct air from out side buttons light up. from what I gather the fan switch has to be on before you can select either of those two buttons. I'm sure it's working fine but it seems odd that with the fan off I get as much air flow as when I do when the fan switch is on 1.

Markeaux · April 19, 2002

OK I see what you're saying. Well for some long time now GM has designed their fans to always blow some air even when the Fan is Off ... I think it was to keep the chance very low of CO2 building up inside.

Shaners · April 19, 2002

I think as long as the vehicle is moving, there will always be some air coming through the ventilation system.

What was the air temp outside?

It is possible that with radient heat from the sun, your cab was actually warmer that the outside air, so the air that was sneaking in the vents felt rather cool.

The easy way to check if the compressor is actually cycling would be to put your truck and park and leave it idle. Pop the hood and look under it and watch to see if the compressor kicks on and off... If it does, it seems kinda strange to me...

2000LTZ71 · April 21, 2002

The first time I noticed this was in the morning so the sun didn't really have a chance to get the inside of the cab heated because it was about 6:00 in the morning. since you mentioned about the compressor I can say that I've never felt the air come through while the truck is parked but still running. I'm sure everything is fine and if chevy has been making there trucks so that there is always some air coming in because of Co2 issues then that makes sense to me.

95Yukon · April 21, 2002

Even with the fan off, when you're moving, the high pressure area at the cowl, or base of the windshield circulates air into the cab, and out through the vents inside the door sills (theres a flap in those to let air out, but not in)

It is to keep some positive pressure in the cab and reduces the chances of any gasses getting in when all the windows are up.

Not sure why it would feel colder, though. If the a/c was on just before that, it may have just been flowing air past the a/c unit which had residual cold(ness)