I have only had my Prius a couple of weeks. 2010 Prius IV, 134K Miles After driving for a while, I hear the fan running in the back seat. At times it is rather loud. Sorta chirping. Advice? Thoughts?
Clean it first. If you continue to hear it, could be it's running at higher or top speed. There are gadgets that can tell you what speed (there are 5~6 speeds), and battery temp as well. If the battery is running hot and full speed fan it might be going. I've seen ours get up to around 140F and fan speed 4 (monitoring with scan gauge) in protracted stop-and-go traffic, but have yet to hear it.
The videos are posted in the Gen3 maintenance sub forum: Nutz About Bolts Prius Maintenance Videos Video #21. Keep us posted .
One comment on an otherwise stellar @NutzAboutBolts video, on accessing the battery fan: you don't have to remove the rear seat. There's one bolt that needs removal, and with a 12 mm socket on a 6" extension, if you push apart the rear seat and back cushions and reach through (a light helps), you can remove the bolt. Reach a hand in too, to keep the bolt from dropping. Another note, the fasteners that hold the hatch floor to the battery case are very tough to pry off. I've left most of them off at reinstall, and the next time went much faster. Also, you can clean the fan without complete removal. Brushes, Q-tips, a dusting boa, and a wet/dry vacuum used both on suck and blow is what I used. I used Scangauge II, whit extra X-Gauges programmed in, to monitor battery temperature sensors (there are 3, with #2 being in the middle of the pack, and tending to be hottest) and fan speed. It's been a while, but I believe this Excel spreadsheet link will have the necessary X-Gauges: https://priuschat.com/attachments/prius-gen-iii-xgauges-11_24_11-xls.34674/ If you don't have Excel, a few screen grabs: BT2 is the one to use, the middle sensor (not sure what BT4 is?): Battery fan speed: AC watts (another one I found interesting: And an indispensible video, on how to *#@% enter X-Gauges: Prius Shop might have the ScanGuage II for sale, but: I'd be cautious, maybe stick to Amazon or others. CleanMPG might also still be selling it. I'm maybe on thin ice to diss our host, but there have been a fair number of reports, of Prius Shop sales that fell through. And so far, no explanation or reasurance that the issues are remedied.
