I would not be surprised by only seeing 11.6V at the fridge. Considering the wiring in the car and the caravan will add up to about 10M all of which has some resistance and when the fridges current passes through it it will cause a voltage drop at the fridge.
After playing with the multimeter,the Voltage is13.4 ,when I turn the fridge on it drops to 11.1volts so I know fridge is working,thanks for quick answers.