Thermostat gets false readings

[314BHDS]

So for a while now I have been chasing gremlins with my heater not working properly,seems most are fixed but I have been noticing something new.My thermostat is mounted on a interior wall and on the back of the cabinet theres the heater on the bottom,the HW heater then a storage compartment.Im away for work and get home to trailer around 2:30 am and it's been a little cool,say low 50's and some 40's.i leave the trailer thermostat(digital one) at 65 deg and I have been coming home with the thermostat reading 68 to 74 but the trailer is cold as heck,if I bump it above the temp it runs fine.I have noticed that my water heater gives off heat inside the cabinet which in turn seems to be giving the thermo a false temp reading and therefore it's not running.There is some un usually large holes drilled for the wires to run to the thermostat that I am gonna try to cover over and hopefully block some of the heat rising up to thermo and fix this issue.

[oldmanAZ]

IIRC, someone else (in JOF?) had a similar problem. They packed the big holes behind the thermostat with pieces of fiberglass batting.

[Jagiven]

If you have a laser thermometer check the wall temp.

If you have access to a small piece of 1/4" thick foam, cut it a bit smaller than the thermostat and place it between the wall and the thermastat. That should isolate it nicely.