I couldn't find a thread on this. My battery fan has started making these pinging-type sounds every time the car hits bumps. It sometimes even happens when I brake. I have been able to replicate the sound, and it is 100% the battery fan, as you can hear in the following video clip: Any idea as to what might be causing this, as it has become more pronounced over time? I did clean out the fan recently. (Mind you, I'm not based in the US, and this car is an import so I can't take it to Toyota)
Did you open it up and look inside? Their could be something really cool in their that'd make this post way more interesting. One time I had a giant moth fly into my cooling fan... Was such an amazing thunk every time it bounced around... OR then there was this one guy on here with a rodent issue... As in let's see what's in there / time to unwrap the present....
I did open up the assembly to the point where I unbolted it from the base and removed the grille. I cleaned the fan's blades because they were very dusty. However, I did not completely dissemble the fan (it has these three very tough screws on the back). Could this be a mechanical issue? It appears to be caused by the fan itself moving back and forth in its assembly possibly.
Personally I wouldn't worry about it as long as it's functioning. It's just barely tapping the inside of it's cover and it's not hitting on a fan blade because the outer "rim" is what's going to hit first. If you no longer hear the ping - then buy a new fan.