So yesterday I decided to check the cooling fan in the back hatch. Disassembling was easy and took less than a half hour. Once every thing was removed I took the upper most duct work off, and then I was able to see the fan. Mine was very clean with only a small about of dust on the blades. I removed the dust using the vacuum cleaner. My Prius is a 2005 with 116,000 on it. A very clean car that I purchased a few weeks ago. After the fan inspection I feel more confident the battery pack has lived a good life so far. I expect to get many more miles and years out of the pack under normal driving conditions.
I checked my fan a couple days ago. It had a small amount of dust on the blades. I couldn't find a small vacuum tip so I used a narrow paintbrush to loosen the dust, then compressed air to blow the dust away.
is the vent on the passenger side of the rear sent the intake or the outtake? the reason I'm asking is i'm wondering how hard it would be to create some sort of air filter for the HV battery fan. I don't drive much on the expressway and prefer to use windows down in the city as it doesn't get too hot here so I probably need this mod more than a person who runs a/c most of the time.