You had the fan positioned properly.
The power supply (major source of heat) is on the left side near the vents.
Pulling air out of the left side will help cool your receiver.
The internal fan is WAY on the other side of the unit and only operates at boot up unless temps get near meltdown (almost useless) and it only blows on the hard drive ignoring all the other heat generating electronics in the receiver - IMHO a crappy design.
I ran my 622 and 722k for 7 years with a fan pulling air out of the left side and it lowered the internal temp as indicated by the HDD temp in the reports by 10 degrees.
I still have the same fan now pulling air out of the right side of my Hopper2000 because Dish reversed the layout of the components. Most of the heat is generated on the right side of the Hopper and on the left side of the 722k.
Edited by Jim5506, 15 July 2013 - 07:04 PM.