Its a 2010 Prius. Does the car give some code for fan not running, or is it a code for for an overheating battery pak, when maybe damave has already been done? Is there some place under the seat, (think on the right) where the fan exhaust port is located that would allow me to feel if there is air flow?
Put a tissue against the grill on the rear passenger seat and see if it sucks it in. It is quiet, so might be difficult to hear unless the pack has an issue telling the fan to run full blast. Or you could disassemble the back of the car and feel on top of the pack as that is where the exhaust is. Good luck and keep us posted .
The grill at the right of the seat is the air intake, not exhaust. When the battery temperature is near 100 degrees F, I cannot hear the fan from the driver's seat with the car parked in READY state. However, for a couple of seconds after pressing the button to shut down the car, I can hear that fan coasting to a stop. That assumes no significant background noise.
I have a ScanGuage plugged into the OBDII port, run the cord to the top of the steering wheel area on the dash so I can read various read outs. One of them can be the fan speed and it helps to manage AC temp in the cabin. I like the tissue paper trick above to check for operation. I can say that the speed varies greatly depending on driving style (charge/discharge) interior cabin and exterior ambient temps.
That's how I monitored it. It's not in SG by default, but can be programmed in, it's an X-Gauge. Another thought: It'd be a good idea to excavate down to the fan, clean it up. Then before putting everything back, go for a test drive, get the car fully warmed up, pull over and see if the fan is spinning. Might also be a lot easier to hear, as you're driving. One thing: uncovered, the battery would probably run cooler, hopefully still warmed up enough to run the fan. When I was monitoring, even on a cool evening, easy driving conditions (ambient temp maybe around 15~18C), I'd see fan speed 1 or 2 (out of 5 or 6?), and temp of the middle sensor (tends to be the warmest) on the pack around 35C.
