An air conditioning
expert once told me that all of these compressor based systems can be improved incrementally, systematically. You gain 10% here, there, etc and soon the entire system is 40% more efficient.
First, follow the advice you got from many about adding a fan or bilge
blower to the compartment where your condenser is. The cooler it is, the better it transfers heat from the fridge.
Second, get an IR temp. gun as mentioned before, and use it to find out where your insulation
or door gasket
is leaking cold.
Third, when you're ready to dig into it, pull the fridge apart and add aluminum
foil to the inside of the hull
behind the fridge. Then remove all insulation
and replace it with Aerogel or Cryogel, whichever is rated higher. It's a lot better than the cheap
insulation that the mfr uses, probably by 2 or 3x. Add aluminum
foil to the inside of the cabinet (outside of the insulation) on the bottom and other 3 sides. Do the same for the door. If there was any appreciable loss through the door seal, consider replacing that with a better version.
I'm not sure what refrigerant is used in your system, but they all work on the same principle of gas expansion which absorbs heat. One thing I've learned about quantity of refrigerant is that it's better to be right on the money
or slightly low than overfilled. Too much refrigerant allows the low side of the system to maintain too high of pressure, which does not allow enough expansion and heat absorption. As the ambient temp. rises, the entire system pressure rises, which unfortunately gives even worse performance when you need it most. A properly charged or slightly undercharged system will be able to maintain maximum pressure differential between high and low side and max. gas expansion, thus max. efficiency. This is in addition to reducing the load on the compressor itself, which wastes precious energy.
It sounds like a lot of work, but it's a one time deal, once you've optimized everything, just enjoy the nice cold fridge!