Heater switch

On a 2001 Pontiac Grand Am, the heater switch does not operate in positions 1 and 2, but works fine in positions 3 and up. I took the switch apart and the contacts look good and appear to work as they should.
Is there a resistor block on the blower motor which controls the fan speed in those switch positions? If so where is the block located?
Does anyone know where I can get a wiring diagram for this vehicle?
Thanks for your help.

Yes there is a resistor on the fan. It is located under the dash next to the fan motor. Purchase it at a dealer for about $40. Will take about an hour to install. Common problem with GM vehicles. As for a diagram if I were you I would buy a Chiltons or Haynes manual they will be quite helpful if you have any other problems.

Same problem