Cabin Air Filter



I recently replaced the cabin air filter in my '02 Taurus. It was plugged solid full of bugs and dirt… But the air had been blowing fine. Replacing the filter made no difference. Where was that air coming from if the filter was so badly clogged? Is the air going through the new filter now?


Your HVAC system probably used an electronically commutated (variable speed) motor that automatically adjusts for differences in static pressure. If it has much more than 3 or 4 speeds and/or is controlled by a digital thermostat, it’s electronically commutated.


Good thought. It’s only got about 4 speeds, though. And I still want to know where the air was coming from. That filter was beyond dirty. It was pretty much plugged solid.


the fan will still blow air even with a plugged cabin air filter.all the cabin filter does is filters the air from outside.the fan just recirculates the stagnate air that is already in your vehicle and sometimes if not changed will make your car smell horrible.


Is the thermostat analog (knobs) or digital (buttons and electronic display)? If it’s digital, there’s a good chance the motor is electronically commutated. Electronically commutated motors are rarely used with analog thermostats, however.
I think the return registers (vents) are always connected to the return plenum, but switching to fresh air opens a damper to let fresh air through the filter into the return plenum and opens another damper to let stale air out. I’m not sure if your HVAC system is designed like that, but it might. (In which case a dirty filter simply prevents the fresh air intake from working.)