Here is a picture of my upper vent, viewed from the inside, with my 140mm "add-on fan" fan (on the side closer to the hitch). As you CR-11x0 owners know already, there is a small fan which is already mounted on the fridge itself - and the built-in Fridge fan does aim, more or less, at the at the "aft-side" edge of the TM upper vent.
The following is a long-winded explanation of the fan. [NEW NOTE: On 8/24/15 I wired the "TM side" computer connector for the fan to an unswitched 12V source, bypassing my previous use of the TM's orginal fan switch. It had merely functioned as another thing to possibly forget when getting ready for the road.]
This is actually one of my "Norcold-assist" fans from years ago, originally put in place to assist the TM-OEM fan. (But the leads are now reversed: It now blows
out through the upper vent between the shells, where it previously sucked in - feeding cool air into the Norcold fins, and eventually sucked out through the TM-OEM fan vent "slinky". The direction of airflow is reversed.)
I removed my second "Norcold assist fan completely, so that the "target area" of the Dometic CR1110's OEM fan (80mm) is unblocked for the somewhat likely situation that (A) I forget to plug in my big "add-on", or the far less likely situation (B) my "add-on" fan (or it's 12V power) somehow fails.
The TM OEM fan pulls air downwards, which is not what you want with the CR-1110. I simply disconnected the leads from that fan, leaving the "dead" fan blades in place to block a lot of possible water entry on wet or slushy roads roads. Or you can remove it completely, as long as you leave the screen in place to block unwanted rodents. That 4" hole, along with the lower fridge vent, is now an extra air
intake for the two fans: My vent-mounted big one, and the CR-1110's own 80mm.
You could also reverse the leads on the original TM-supplied fan, so that it blows air upwards. (EDIT 8/2/15) But I don't think it is needed at all, I capped off the "hot" lead, and removed the original TM fan completely. With that computer connector in at the top vent, I can still remove the vent (when necessary for cleaning ro replacement of the fan, or to take the attached picture
). You see the fan-side 12V connector at the top of the picture (it's upside-down, compared to it's installed position).
For efficiency, I taped up the rest of the "fan mount" side with UL-181B flex duct tape. (the kind which doesn't give way under heat or vibration). This prevents air from coming in the sides of the vent, doing nothing for the fridge, and blowing out the top. I also taped about half of the opposite side, allowing a small area for the CR-11x0 "OEM" fan to blow outwards if the "add-on" fan isn't running. (Although I am now turning it once at the start of each trip, and leaving it "on" for the entire duration - because it's absolutely silent and doesn't use much power.) This moves a lot of air, and consumes (SWAG) 4-8 watts - more power when shells are down, less power when shells are up in camp.
CR-1110 upper vent fan (add-on/replacement of TM fan).
Hybrid Mode
