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Don't Forget! Change Your Cabin Air Filter!


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2009 Nissan Sentra in the shop today with inop. blower motor.

Two other shops told the owner she needed the entire HVAC box because the blower is not replaceable without removing the whole box, which requires removing the dash to replace.

 

I spent about 30 minutes dissecting and found the blower worked fine when the Resistor module was bypassed. Needs a blower resistor, simple fix! But why, when this 6 year old car only has 75k miles, has this part failed?

 

Cabin air filter. Totally clogged with leaves, dirt, and dog fur.

 

Blower resistor module gets hot when the fan is running. The blower fan blows air across it to keep it cool, until the airflow gets blocked by leaves and crud. Insufficient airflow, module overheats, burns out, no more fan!

 

After some researching found out this particular unit has a thermal fuse. If it gets too hot the fuse burns, and then no more fan, but you can't replace just the thermal, you have to replace the whole module, which is about $120 from Nissan. (Plus a couple hours labor to diagnose and replace it) Or if you're adventurous, you can take it apart and solder in a new thermal fuse.

Not all resistor modules can be repaired though.

 

Change that $10 filter once a year and save yourself the expense of having to buy an expensive resistor block! At the very least pull the thing out and knock the dirt out of it.

 

Sorry, it's not a Subaru story, but its helpful advice for any car with a cabin air filter!

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HVAC blower resistors have been failing for years, in my 2003 Jeep Liberty, in our Dodge Ram pickups too.  So it is something that just fails.   BTW, the resistor "works" the hardest when the blower motor is used on low speed.  Most resistors when they fail allow the blower motor to run at top speed-high only.

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Another blower problem yesterday on a 07 FJ cruiser. The cabin filter was disgusting. But on this one there is a tray thing that was supposed to hold the filter which was gone, so it was just kind of sitting on top of the blower motor. A bunch of crud had made it past the filter and into the heater core/evaporator core box and clogged the drain tube. The resistor module and blower motor had both been flooded with water and rusted. Module was toast. Motor would work for a few seconds if I spun it by hand. I did manage to get it working after removing it but I dont think it will last long. I sprayed contact cleaner and wd40 all down into the motor case to try and loosen up the brushes. Shot Compressed air in it to help remove some of the scale. Got it to work OK when it was connected straight to a battery but back in the car I had to smack the case to get it to spin at more than about 1/2 speed.

 

Car belongs to a woman with two small children, one with special needs, so she needs the AC in our hot and humid weather.

Toyota here in town had a resistor for $30, but neither Toyota or any or the parts stores could get the motor ($160 from Toyota, about $100 aftermarket) until next week.

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