Just a point of clarification. Inside the circuit board box are TWO fuses. One is 12VDC and the other is 120VAC. Which fuse kept blowing? I'm not in the "use it til it blows camp". This usually leads to bad and expensive repairs. There's a reason why the fuse keeps blowing. That should be addressed and repaired before using the fridge.
There is a short somewhere that's causing the problem. I would suspect the problem crops up after the elements get hot. This points to two areas, the heating elements and/or the circuit board itself.
Start with some easy stuff first. Pull off the outside inspection door and run a check of EVERY wire and CONNECTION behind that panel. Make sure they're tight and not corroded. Look inside the circuit board box, where you found the fuses, and look for any discoloration that might indicate short circuiting or damage. Determine which fuse continues to blow....12v or 120v..that might help in tracking the problem further.....Dennis