Fridge coldness while en route

We have made a few trips now with our TM since we purchased it a couple of months ago (new to us). While travelling the refrigerator seems to cool very poorly. I have replaced the fan on the underside after our first trip because the old one barely turned. The temperature outside ranged from 60 to 100 degrees while on the road. It just doesn't seem to work as good as our old trailers refrig. Any ideas? Is this mainly because of the lack of circulation on collapsed TM?
Thanks
winsail