Yes, there is a fan in the Dometic.  I finally dug out my manual for my
Dometic 182 and it says: "....a 0.6 watt ventilator [fan] is switched on
automatically when the temperature around the condenser fins is about
126 F and switched off at 108 F.  The ventilator is connected to the
twelve volt system."

Unfortunately, in the Vanagon installation the twelve volt system is
only working when the engine is running!  The fan will not come on with
gas or 120v AC unless you rewire the system.

No wonder I have never heard it!

Stuart