Hey guys, first time poster here. I have a 2002 Chevy Express Cargo Van. I've had it for a few months now, and have noticed something strange with the A/C and fan.

1. Positions 2, 3, and HI work fine with Max A/C, A/C, and just fan

2. Position LO puts out air on A/C and just fan when I"m driving. When I'm stopped, there's no air movement (but I hear the compressor kicking in if it's on AC). Once I hit the gas pedal, I feel air coming through. If I'm cruising above 25, I also feel air, regardless of whether or not I'm hitting the gas.

3. Position LO does not put out anything on Max A/C (again, I hear the compressor running though) whether or not the van is moving.

4. Positions 2,3 and HI blow out the correct amount of air. It doesn't feel weak at all.

Any ideas?? Something electrical in the control *****? The blower motor? Thanks for any help you can provide!

 

The fan speed on lo is very lo. Driving will make more air come through.
The fan switch does not engage the compressor. Only ac, bi lev, max air and the defrost settings do.
The best way to feel for air movement on lo setting is to put your hand over the vent on the left of the dash that blows air on the drivers window. You will feel it there.
I have the same year van, and I find that lo is too low, and med is too high. I have to switch back and forth all the time to maintain a nice temp.

 

I think you may have a vaccum leak in the air controls. Check that the vaccum is attached under the battery, there is an extra vaccum storage tank under there. Its the black ball the size of a large grapefruit. It has one port on it. The line will come off the tank and "T" about 12 inches out, one way goes to the intake plennum for source vaccum and the other goes to the dash controls.
Eric