Most Dometics have the slider; it's inside the fridge. But some have a 3 position switch on the outside front of the fridge.
Fridges in slides don't have a roof vent, they have a upper side vent. So they have a harder time working as they don't get the same "chimney" effect for cooling that the non-slide ones do. That's why many of them have a fan installed, but from my reading of posts here, it doesn't sound like it's much of a fan. Lots of folks have added computer fans.
If you want better answers, suggest you post your model number.
1988 Coleman Sequoia - popup (1987-2009) - outlasted 3 Dodge Grand Caravans!
2012 Roo19 - hybid (2012-2015)
2016 Mini Lite 2503S - tt (2015 - ???)
2011 Traverse LT, 3.6L, FWD
2009 Silverado 1500 Ext Cab, 5.3L, 4x4, 3.73
2016 Silverado 2500HD Dbl Cab, 6.0L 4x4, 4.10