One thing I have seen on MY Coleman (And others as well)
The concenser coils (The ones on the outside) Get clogged. now on a coleman this is simple You need.. One each Phillips head screwdriver #2 or 3 should do it.
That's all folks. a soft bristle brush may help too (Like a dusting brush or shoe brush. or even a hair brush)
Up on the roof and look at the thing. if you can not clearly see the fins. use srewdriver to remove 4 screw head bolts on top and the washer under them
Lift cover and peal then brush the crud off.
Replace cover, washer and bolts
It now will work better
ON MINE when it cruds up it will trip the breaker
OTHER MODELS
You have more screws to remove (#2 driver still works, I use a battery driver for these) then you have an inner cover as well that has to be opened. Some it's just screws. Mine it's tape and bend tabs and that's why it now has a coleman fan so I dont' have to do that. but the coleman fan does not cool the condenser as well it seems as I have to do a lot more cleaning on that unit.