I would either move the battery or as someonme suggested cut an access hole, also seal the battery comparttment with regard to INSIDE and vent it to OUTSIDE, in fact it should be that way now but sounds like they did not.
Sounds like whoever designed that RV went to the Auto Engineer's school of design.. There is a story about Henry Ford, this is the very short version:
They brought him a design for a Carburator 14 Screws "Too many screws"
They tried again this time only 4 Screws "Still too many screws"
The final design had a single screw that you needed to remove to D&C the Carb "Just right".
Alas he's gone now.. In 1970 to replace a heater core you clamped the hose (Who drains the cooling system) removed them from teh heater core, took about a dozen screws out of the cover plate and lifted the thing out... Dropped in the new one, fill with antifreeze, apply cover and screws, re-attach hoses and un-clamp job done (run engine a while and add coolant as needed).
Today.. Evaucate A/C . disconnect lineds at fire wall and seal off
Clamp and remove heater hoses (As above) (like I said, who drains the system?)_
Take apart (most cars) the passanger side of the dash board, slide A/C Evaporator out on it's rails and remove heater core from behind it.
Renault.> Remove STEERING COLUMN, open heater compartment and remove heater core to replace (There is an easier way but this is the official 3 hours job method).
As I said. Henry is no longer with us.
