2007 tC

A week ago (9/14), my "check engine" light came on. I brought the car in to a shop, and the diagnosis was that the carbon canister needed replacement. This was done a few days ago (9/17) when the shop was able to get the part. The shop also replaced the TPMS sensors, as three of the four had failed.

Yesterday (9/20), about 30 miles total since the repair, multiple panel lights (including "ABS" and "brake") came on, and the A/C started blowing at the max (despite being set to 1). When I turned off the A/C, things went back to normal, except the "check engine" light remained on. I brought the car back to the shop, and the diagnosis was that something was amiss with the vehicle speed sensor. After a hard reset of the computer, things seemed like they might be all normal, except the battery light was initially on (maybe from the car being idle during the diagnosis?).

Things seem normal now (no battery light), except my radio volume is really low. I usually listen at volume 7, but now I need to crank the volume up around 21 to get similar sound. Does this seem like it could be from a weak battery? (It has been a while since I've replaced the battery.) Alternator? The previous time my alternator needed replacement, there were more obvious signs like the clock being reset and the battery light coming on whenever the car idled. TIA

Edit: Probably unrelated, but mentioning just in case... I also found that my driver's side control for the passenger window isn't working now. The control on the passenger door does operate the window properly.