Hi SandyG,
I have a Vendo 56 Squaretop, which is very similar to a Vendo 63, and it is normal to for the evap fan to stay on even when the compressor is switched off.
Here is another reason not to mess with the fan. If the fan isn't blowing out the cold air and keeping the area cool, the temp sensor might engage the compressor more than would be normal.
When i originally bought my machine, the temp sensor wire was folded up and tucked away in the bottom corner of the fridge. However, from the many photos of other Vendo 56 and 63 machines I had taken and downloaded over the years, and few manuals, I found that the temp probe wire was stretched out and the tip with the probe was located above the air fan, directly in the airflow.
I made the change, and found the compressor engaged less often than before, and for a shorter period of time. And the drinks were nice and cold
As for increased costs, i find that setting aside $7-$14 a week pretty much covers the added cost of running a machine.
Got any photos of the machine inside and out? Am a fan of the 56/63's, and always like to compare machines, see how they are setup etc.