Rear Seat Fan Running Frequently

No, it's a good thing...cools your hybrid (traction) battery located under the rear seat!

Be sure to service that little air filter that's there, too...and while you have the door open shine a light and inspect the round fan, make sure it's not clogged up. (I have dogs so I check the fan and filter often.)

 

The fan that draws in air from the vents near the rear passenger seat uses that air to cool the high voltage traction battery, not the smaller 12 volt battery. If you're hearing the fan running loud or often, it would simply be because the car has judged that the traction battery is too warm and needs to cool off, so it draws in cabin air and passes it through the battery pack. Hot weather could be one cause (I probably wouldn't judge 50-60 °F as hot, but 50-60 °C I would). Spirited driving could be another.

I wouldn't worry about it too much, but it might help be worth your while to ensure that the vent (and the duct behind it) is free and relatively clear of debris.

 

It doesn't have anything to do with the 12 volt.

Your hybrid / high voltage battery might be running hot, which means you have a cell in the pack that is going to fail soon... To confirm buy one of these: Panlong OBD2 Scanner Bluetooth OBDII Diagnostic Tool Car Code Reader Turn Off... | eBay and use Dr. Prius app on your phone to monitor hybrid battery temperatures.

Also, if you let us know what region in the US you live, someone on here might live close enough to you to help you save a ton of money!

 

definitely clean the fan

 

This is the best person we have for you in your region... He's a mobile mechanic based in Oklahoma and is a fast reply when it comes to helping people via messaging: Drew Griffin (skimmilkhybrid) • Instagram photos and videos

 

Another, video #21 here:

Nutz About Bolts Prius Maintenance Videos | PriusChat

comments on the video:

1. I found it not necessary to pull out the rear seat, per the video: there’s one (12 mm socket size) bolt, just below fan intake grill, that you need to remove. Just push apart the seat bottom and back and it’s reachable.

2. Forget if they do this, but anyway: fan can be cleaned without complete removal; q-tips work good for getting in between its fins.