We have a 2010 Prius Type 5 with about 18K miles. I've noticed at times that after having parked the car in the garage for several hours, that there is a soft "whirring" sound on the passenger side rear of the car. I'm assuming this is the battery fan, because it sounds like a fan and I can't think of anything else back there that would make a "fan"-like sound? Is there any other device back there that could make a "fan"-like sound while parked (it's cold weather here, so it's probably around 40 deg. F or less in the garage)? It makes this noise for 5-10 min. and then stops. If this is the battery fan, why would it run when the car is cold?
It is the battery fan. I hear it from time to time on my own 2011. There's a small grille there in back to the lower rear seat that shouldn't be blocked. It adds airflow to the hybrid battery. I heard it a lot more on my old 2007 than I do on this 2011, even thought the new car is black and gets hotter by far!
Do you know why it runs after the car has been parked for several hours in the garage, even in cold weather?
I remember my 2010 came with a Notice placard that said something to the extent that it was normal for the car to make sounds several hours after it was parked. I know with conventional vehicles the emission system will perform integrity checks hours after being parked by pressurizing the fuel EVAP system and check for leaks. Perhaps this is whats going on. I don't see why it would be the battery fan when the vehicle has been off for hours.
Don't know--definitely sounds like a fan running and it's in the vicinity of the passenger side rear tire...
Well, if it is indeed performing pressurization checks of the EVAP system, it would be using a small electric-motor driven pump. This is just a guess, but that is what conventional vehicles would use. Perhaps a wiser member will know exactly what it is.
It cannot hurt to bring it into the service department and have them check it out. I think it's normal at certain times, but it's best to check it when it's under warranty. Maybe it wants to keep the battery at closer to room temp than frozen? I was going to ask if you had a sunroof ... but I see you have a 5. Thus, it's only the back pass side rear. No harm in getting it checked. That area down there, is anything blocking it at all?
Re. any blocking, no, nothing is blocked and everything is stock. More of a curiousity on my part--it seems to happen randomly, but usually after it's been parked several hours. I seem to have noticed it more since it's been cold than back in the summer.
I have no Gen 3, but my 2nd gen came w/a card that said: I posted about it at http://priuschat.com/forums/gen-ii-prius-main-forum/20869-noise.html. I personally have heard the above evap check when in the garage, more than once and IIRC, it was a light whirring sound. And yes, it was about 5 hours after I'd stopped the car. If the 2010 came w/such a card, then it's likely the same thing.
Yup, it's most probably the evap system pressure check. The fan only runs when the battery is hot, and I've never seen that happen in winter. At least in -real- winter.
I'm going to have to consult the owner's manual/search for my card, but it sounds like you've solved it--I do believe it's in that 5 hour timeframe--thanks!!!
The 2010 does the same. While I saw it in the owners manual immediately, the timing is such that I didn't hear it until the car was almost two years old, and have heard it only a couple of time since.
When we were 'kicking tires' before we had made our purchase, this was one of the things that the salesman warned us about. Good guy! I am glad, just so it is in the back of my mind. I have never heard it come on. But when I do, I already know what it is. No big deal.
Agreed, the EVAP check only runs when the car is off.. And has been for several hours, there should be mention of it in the owner's manual.. And it's closest to the passenger rear tire, it can run for several minutes
I haven't noticed this yet with my Prius c, but what you describe happened with our 2012 Sienna. Clearly not a battery fan on a non-hybrid. More likely one of the other helpful explanations offered on this thread. Anyway, I turned the ignition on and off and the noise stopped.
