The area on both sides of the firewall where all the AC stuff is on the passengers side gets quite warm when I am driving. Actually, it is borderline hot. There is a hum or vibration from that area as well that concerns me. This is with the heat and AC off and fan not blowing.
What is inside there and what might be going on???
There’s lots of stuff in there, could be wild animals but more than likely your moving hot water through your heater core from the engine. Install a simple shut off valve in the heater hose that runs from the water pump to the heater. You will need to open the valve if you need heat or defrosters.
As for the vibration, could be a number of things maybe someone will chime in with ideas, I’d pull the fuse for the heater/AC blower and see if it goes away.