2001 chevy silverado a/c switch not working on settings one and two

SOURCE: 2004 Chevy Silverado Heater Switch

It could be the switch or your blower motor resistor.

SOURCE: air conditioning silverado

The problem is in the heater box. To be more specific, the blend door. Check blend door operation and blend door motor. Located right side under dash. Remove blend door motor, with vehicle running, move switch from panel to defog and see if blend door motor moves.

SOURCE: 2001 Chevy Venture weak front A/C blowers

you either need a new blower, blower motor resistor , or the air inlet to the blower housing is clogged. Also if it has a cabin air filter that may be clogged also.

SOURCE: Air conditioning relay switch - 2001 Ford Tauras

there is usually a relay block (black in color) either on the right or left side under the hood, and in front of the wheel well. Don't discount the possibility that you may have a bad pressure switch on the line. That is a safety device that is now installed on most all vehicles. If you turn on your defrost, you should hear the clutch on your AC clicking on and off. If you do, there is another issue. If you don't, then listen for a faint clicking. This is a small relay so it maybe very hard to hear, even if you found it. You many actually have to lightly put a finger on the relay cube to see if you can feel it clicking. If this is clicking, but the AC is not kicking in and out, replace the relay. If this is NOT clicking with the defrost on, then it is not being told that it is ok to. This may be the pressure switch that drops out if the freon is too low, or too high.

SOURCE: knock sensor on 2001 chevy silverado

on the 4.3l version the knock sensor is on the back left side of the engine right by the bell housing. on the bigger engines they are below the intake manifold in the engine valley