If you want to replace your 3 way fridge with another 3 way fridge, you could first try various measures for improving how your current fridge works:
- After pre-cooling the fridge, load it up with frozen stuff (food and ice) just before leaving. The larger the ice chunks the better, e.g., quart or larger containers.
- Improve ventilation behind the fridge by taking off both vent covers and cleaning all coils and fins.
- Add a 12vdc fan behind the fridge.
- Open the lower fridge vent on warm days.
- Use a remote weather station sensor to monitor temperature. We adjust the temp dial warmer at night (else the food freezes), and cooler during day to keep the temp between 32 and 40 degrees F.
We have a Dometic fridge in our 1978 Trillium
EDIT: Another tactic we use is to freeze water in plastic containers in the Dometic freezer at night, and then move them to the fridge section during the day (then back to freezer section at night).