Dometic (Waeco CB36) Problematic

[BongoFredaLili]

We have a Dometic (Waeco CB36) fridge in our Ford Freda, which has stopped working, it comes on for 5 seconds then shuts down... An engineer looked at it this morning and said he is not familiar with these although he works on caravan & motorhome fridges... We are at a loss as to where to go with this... it has been suggested that it could be the thermostat or start capacitor. Help with this would be hugely appreciated... Thank you

[g8dhe]

When you say it comes on for 5 seconds and then shuts down that sounds very much like the cooling fan powering up, then when the compressor attempts to turn on the voltage drops from the 12 volt source and the system shuts down.
Check the voltage as close as possible to the fridge, it needs to be above 12 volts as the compressors have a low-voltage cut-out built in to prevent draining the LB totally, it might be a flat LB or a dirty fuse or switch causing the voltage drop, most frequently its the LB needs a charge or is on its last legs after several years use!