We also had the noisy fan issue with our Cougar
Any camper models with the frig in the slideout
will have no venting to the roof
So the frig unit is cooled by these fans
and are activated on a hot day by a thermostat
For us, having the frig in a slideout was new so we went from
no frig noisy at all to the hi pitched fan running
My dealer told me that this noisy was normal for Dometic
I didnt believe it so I contacted Dometic
They responded with telling me the fan should not be noisy
Told me the correct order # to give to my dealer and have him replace the noisy fan
The dealer ordered the new fan, replaced the old fan
and all is good now
Hope this helps you