FWIW,
Had a problem with my Waeco last year on a 2007 278 Vista. Fridge would not get very get cold but compressor appeared to be running on AC or DC only. (in reality compressor would toggle off but fan was still running). The hotter it was outside the worse the refrigerator performed.
The refrigerator uses a 12 volt compressor. There is a power supply or "brick" with both 120vac and ship 12vdc input and 12-24v output. This output goes to a control box on the back of the fridge that supplies power to the compressor. The supply or "brick" will switch to ship DC in order to power the compressor in the absence of 120VAC into the supply. It turned out that the "brick" 120 volt power supply was faulty.
In my case the power supply was toggling back and forth from ship AC to ship DC as the source power. Its output DC voltage would slowly drop under load below a threshold, probably a faulty voltage regulator. When this occurred the compressor would shut down. The supply would switch over to ship DC as the input source of power. Under no load the DC provided by the power supply would go back up and the supply would toggle off of ship DC as the source back to the supply DC and the cycle would repeat. It appeared the higher the air temperature the more consistent the toggling became and the lesser the refrigerator cooled. The control unit prevents the compressor from immediately restarting for a set amount of time 1-2 min everytime voltage was interrupted. The compressor would not run very long.
Can be hard to troubleshoot as the protection timing involved in the control unit wasn't obvious at first. I read somewhere else that the original MP-35 supply was borderline as far as being strong enough for that compressor, which probably led to it's early death. I went to a larger capacity power supply, MPS-50, $75 fix. Had to mount the brick in a different location as it was slightly larger than the original MPS-35. A lot cheaper than a new Fridge that might not of been an exact replacement fit. The fridge worked great rest of the year, think this cycling issue had been going on for a while appearing as poor performance in higher temps and just kept getting worse until it would no longer keep the compressor running long enough to cool.
https://www.google.com/search?q=MPS-50&ie=utf-8&oe=utf-8(Update - lasted two years, seems I sprung a leak between compressor and cooling plate as there is a some oil residue in the freezer. Trying to find someone to repair, otherwise $800? Closest replacement I can find but seems discontinued is Dometic CRX-1065 or Norcold NRB 751BB)