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: 119,000 mi (100,000 mi - 145,000 mi)
Visitor, 2000 GMC Sonoma, 145,000 mi
HVAC Blower motor works at 1,2,3 and fails on number 4 setting
Visitor, 2001 GMC Sonoma, 100,000 mi
Third time it has blown. Seems they last less than a year. Blew out totally on all speeds twice. This last time it was just the high speed. Replaced the resister all 3 times. They are guaranteed for a year. Lost last receipt. Paid for current replacement ($20) so I am waiting a couple of months and going to turn in my bad one for a new one. That way, I will have one on hand to change next time as this seems to be an ongoing issue. At least they are easy to access to change. This time though, I went into the fuse panels and pulled and applied dielectric grease to all fuses. Perhaps weak/ faulty-corroded connections? Probably not but nothing to loose. Seems resister craps out when changing blower speeds or switching off/ on. Too bad. This thing has a kick ass high speed blower system. Is it being caused by a voltage spike from the blower speed switch? Dunno.
It is as if the AC stops working. But this problem shows up in the middle of summer when I am using the AC the most. I just stop getting cool air and then there is no air blowing through the vents at all. Not much I can do but turn everything off and roll the windows down.
Setting I and II wouldn't work. Replace Resistor to fix.