The OP hasn't provided any details about the make / model of fridge he has but on Page 18 of this
Dometic RM Series Diagnostic Service Manual it states (in part) ...
5.11 Climate Control Heater & Switch
Not used on all units.
5.12 Low Ambient Switch
Not used on all units.For a complete explanation click on the above link. I repeat, my particular
DM2652 does
not have any of these switches and does
not offer any way of manually controlling these circuits despite what others may claim. It's entirely possible that the interior light in the OP's fridge is
intended to be periodically turned on when the main fridge door is closed ... if continuity tests show any switches his particular fridge has are fine then perhaps he's trying to fix a problem that isn't. :R
