1999 Pontiac Bonneville blower motor

1- Take a 12v light bulb (2 pin headlight) and wire it in the connector for the blower motor and see if it will light and control the light at different brightnesses. This check power and ground and will load the circuit. If light doesn't light, check for voltage and ground at blower connector wires. Usually will have only one missing depending on how it is controlled. This will also check the resister if headlight works. To eliminate ign sw. check at control head for the ignition input voltage so you don't have to guess. If not there it is a wire broken or the ign sw. If you know the blower works, it makes it easier to diagnosis right? To simplify wiring diagrams working backwards is a good idea as posted, but also try to find a way to cut the circuit in half and check voltages and grounds. IE. connector,relay or switch.
If it lights up the blower motor is no good, if it doesnt either the switch or ignition switch needs testing/replacing. Dont forget the fuses!
HVAC control-20 amp DIC/HVAC-10 amp and HVAC hi-30 amp