I have an Electrolux fridge in my van in Europe, which is almost exactly the same as the Dometic I have at home.  I managed to light it up quite easy, but it won’t cool any.  I turned it upside down for one night.  Now the gas is burning for three days but it won’t start the cooling.  
The 220V heater element is faulty, won’t heat.  But I’m thinking, if it won’t cool with the gas burner, it’s useless to buy the electric heater unit for it.  I am ready to buy an other fridge but I can’t find one on German Ebay.  
Anyone would know what is possibly wrong with the system?  Would there be something wrong with the liquid gas?  Is it possible to add to it if it’s not enough?  Etc.  
Zoltan