In my rig, it's clear across the rig from the battery compartment in a tiny compartment under the sink. But, can't seem to get to it from there. Looks like in my case they built the RV around that cubby hole. Point is, they'll put them where ever they can fit them.
When I had to find mine, I disconnected the batteries while plugged into shore power, found which big wire still had 14V on it, and traced that big cable back to the converter compartment.