The '90 PA would not have a BCC. It also would not have a Diode based Isolator.
These linked diagrams are actually for an '89 Bounder, but are typical of your vintage Pace.
The first page shows how the batteries were originally wired by Fleetwood.
The coach was built with one (1) 12volt starting battery and two (2) 6volt aux/coach batteries (wired in series)
The only direct connection between the starting battery and the aux batteries should be through the Isolator solenoid.
There is a device installed (called an IRD - Isolator Relay Delay) that is used to close the Isolator relay for the purpose of charging all the batteries together while the engine is running.
The relay can also be closed via depressing the aux start switch on the dash. These functions can be viewed on subsequent pages of the diagrams.
I suggest calling Fleetwood RV Customer Support to request diagrams specific to your coach. They will e-mail them almost immediately.
