The HVAC blower motor may stop working at one or more speeds due to a faulty blower motor resistor block. Our technicians recommend to confirm the resistor is at fault by first checking the operation of the switch.Google+
Car Problem Reports
GMC Sonoma AC Blower Inop Due to Failed Resistor
GMC Sonoma Problem
Average Mileage: 125,333 mi (110,000 mi - 145,000 mi)
Setting I and II wouldn't work. Replace Resistor to fix.
Visitor, 2000 GMC Sonoma, 145,000 mi
HVAC Blower motor works at 1,2,3 and fails on number 4 setting