The fridge looked like it worked in that when you opened it there was a green light, green usually means good or go, in this case it meant more bad wiring.
Upon investigation, for a Waeco 12v fridge to actually work with a leisure battery you have to have as few connections and the shortest cable run between the battery and the fridge along with 6-8mm 10 amp cable plus an inline fuse. If you don’t follow these rules you will suffer from voltage drop which means the compressor will never receive enough voltage to fire up and cool your fridge. This is generally indicated by two things, one, a warm fridge, two, a red flashing LED by the thermostat control in the fridge.
Whoever did the conversion used the same kind of cable you would use to wire up a door bell, then before it reached the battery the cable was wired into a PMS3h management system and then to a rocker switch and then to the battery, it will never work like this but it did give a green light and the internal light worked. The fridge was getting voltage but not enough to operate. Based on everything I had read on the forums I pulled all the original wiring out, wired direct to the battery with the correct gauge cable and we now have a working fridge, result, especially when transporting cheese. To turn the fridge off when it’s not in use turn the thermostat control past the 0 point, you will feel a little resistance but it will click and the light will go out.
Since returning from our holiday in France i’ve wired the fridge up a little differently, it’s now wired directly to the PMS3h but not to either of the connectors labelled fridge, there is an aux 12v output on the back of the PMS3h, I’ve hooked the fridge up to that and I will tell you why.
If you look on any of the forums the general rule of thumb to wiring up your Waeco CR50 fridge is as I have described above, wiring it in this way prevents voltage drop which will stop the fridge from working. We have a 240v hook that feeds into a PMS3h, the PMS3h when hooked up to 240v supplies the leisure battery with a (paltry) top up charge, however, if you have the fridge directly wired to your leisure battery then the fridge (if switched on) will still be pulling power directly from the battery even though your van is hooked up to 240v, this means that the small top up charge the PMS3h supplies to your leisure battery is not sufficient to top up the battery as the fridge is still drawing more voltage from the battery than the top up supply feeds in, the result being your battery eventually dies along with your fridge.
Wiring it up as I have means that when I am hooked up to 240v the PMS supplies the fridge with 12v, not the battery, the battery can then be topped up by the PMS3h while the fridge continues to operate without sucking the life out of the battery.
You still need to use the correct gauge cable as specified by the manufacturer, make the run as short as possible and avoid any additional connections like rocker switches !
IMO, if you have a PMS3h and 240v hook up then this is a more efficient way to wire in your Waeco CR50 fridge.