2002 express van when ac is on hot air is blowing.

I looked at a couple Express engine pictures and I know what you mean. It's a van where you can only see a small portion on the top. --- If the A/C is on, you should hear the A/C clutch pull in and release. It has a sound all of it's own. --- Your problem could be that the HVAC system temperature control door is stuck closed. That would blow heat all the time. It's not stuck if you can change temperatures. --- The other scenario is that the compressor is shot or the fuse is blown. If you can hear the clutch cycling, the fuse is good. --- To find the compressor, try to follow the serpentine belt. It goes around the crank, the alternator, a idler pulley and the A/C compressor. It might go to the power steering pump and the water pump. That depends on the engine and maker. The GM vehicles I am familiar with have the compressor down low. There a condenser that looks like a radiator that's in front of the radiator. It has a couple of fluid pipes attached to it. Follow the pipes. One it bolted to the A/C compressor.

Why air keep blowing from under the dashboard while driving since no heat and no ac is on.and the faster you drive the sronger the air blow.and if the weather is kind cool arond 60 degrees. You freez to death and thats a chevy gargo express van2017 van.