on my previous RV, a DP, i put a fan in the top of the fridge roof vent
wired it directly to the solar panel wires "at the roof"
the wires went down thru the fridge compartment thru the floor and into the basement storage where the solar controller is at
(yes with either PWM or MPPT controller these were 12v panels with an operating voltage of 17.x)
that fan ran directly from solar power, the batteries and controller and solar were always all connected, unless i was working on the batteries for some reason
its that simple, just keep the voltage in range,
Diodes should NOT be needed, BUT if used, the go in the FAN WIRES not the panel output wires
"oh God" is an exclamation of exasperation
and i think it fits quite well in this chain of posts
