Blower will not turn on

BOSTON2PHX

MEMBER
2012 CHEVROLET SONIC
172,000 MILES

So in July the pigtail to the relay went bad and the blower sounded bad so I replaced the relay, pigtail that melted and the motor since it sounded like it was on its last leg. Everything was fine after until last week the blower turned off. So I replaced the fuses, nothing, checked the blower in case it was faulty, it's good. Relay and pigtail are good, compressor is working, clutch is working, when I flip on the interior climate control nob I can hear it turning on and my pipes get frosty, but my blower stays dead. Completely stumped. Any ideas out there?

1 Reply

KASEKENNY

MECHANIC
18,907 POSTS

Hi,

The way this works is the HVAC control module supplies voltage to the blower motor and it goes through a fuse then to the blower motor. If you tested the motor and it is okay and the fuse is okay, then you need to look at the resistor. This is what is called a ground side control. Meaning we add a resistance through the resistor after the motor that causes the motor to spin slower. The higher the resistance after the motor the slower it goes. Remember when we introduce resistance to a circuit then that voltage gets spread out to both loads. So instead of the motor using all the voltage, the resistor requires voltage which causes the motor to spin slower.

To diagnose this, you need to go to the motor with it hooked up properly and see if you have voltage coming to it on Pin 2. If there is no voltage on either wire with the motor turned on then you know it is either the HVAC module, wiring, or fuse. If there is voltage getting to the motor, then the resistor is open, wiring is open, or the switch has failed.

Let me know what you find and we can go from there. Thanks

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Blower will not turn on

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