Cruz-in
If you have a Norcold Model reefer, they have a magnetic door switch that is located right under the on/off button on the control panel.
Take a magnet and slide it along the recessed door lip and the interior light will turn off and on.
I installed a couple of the small blue colored fans inside my reefer,
I got the power from the circuit board wire, 12v, that is HOT all the time.
To get the small wire to the fans, I removed the control panel, I used the OEM holes to run a 17 cal cleaning rod with pointed tip jag for pushing patches, to make a hole to the inside of the reefer.
I carefully removed the light and pushed the cleaning rod thru the strafoam and into the light recess, (after some carefull calculation on angles/depths etc), then I put on a slotted tip and fed the wire into the light recess.
Ran the wire to the fans across the roof, removed the excess wire, sealed the 17 cal hole with foam from both ends and attached to the Red/white hot wire 12v (IIRR) going to the curcuit board.
Reattached the OEM lite, attached the circuit board in it's place etc.
I added 2-90mm fans in the back flue, picked up a constant 12V hot wire on the curcuit board, inside the flue, used a piggy back connector and then added a 85* attic switch that turns on at over 85* and shut off at below 85* to run these fans.
I also install a simple disconnect to the main wire curcuit to keep the power off when NOT needed.
MAKES all the difference here in the summer time, since we have very little shade trees etc.
Hope this helps,
Tia,
Don