I’m having problem with my 12v cool box/ fridge that I got about 5 years ago, when is plug in during the day fine no problem but when I left plugged in over night seems to draw all the power from daf xf battery, I had a issue over winter when my night heater was cutting out due to low volt. but since then I had brand new battery fitted, and always left the fridge unplug saved me a call out to jump start, last night forgot to unplug the fridge and the truck straggle to turn over, could this be faulty fridge that just draw to much current, the other thing is I need to have my ignition on nr1 to get the power to 12v socket could this mean is running from dropper?
Well it’s not faulty, it’s just that aftermarket cool boxes draw a lot of current so it’s never a good idea to leave them plugged in for long periods if the engine isn’t running. Factory-fitted fridges work in a totally different way, draw far less current and generally turn themselves off if the batteries start running low.
i’ve had one of the large halfords cool boxes for years,it gets plugged in monday morning and unplugged friday night when i get home, and i have never had a problem with batteries going flat with just the box on, had problem using the inverter to run my lappy and not running the truck up before i go to bed at night. the problem might be with the key being in postion 1 as that might be sending power to other things 
Thanks Harry, the only problem is I did run the cool box for few or at least a year 24/7 no problems until last winter, where the battery had low volt., since then after few cold nights due to night heater wasn’t working I decided I will leave the fridge unplug until last night, I know the in build fridge will have 24v low volt cut out at around 21v I think but if I was to get on of them waeco 24v will this work in same way■■? also don’t want to spend nearly £200 on something that is not the problem.
Maybe some will know what is the volt on battery when engine is running, could check that the alternator working correctly? Maybe is no charging the battery to is full potential during they.
wildfire:
i’ve had one of the large halfords cool boxes for years,it gets plugged in monday morning and unplugged friday night when i get home, and i have never had a problem with batteries going flat with just the box on, had problem using the inverter to run my lappy and not running the truck up before i go to bed at night. the problem might be with the key being in postion 1 as that might be sending power to other things
The only thing that is running when key on 1 is power to radio, I have another 12v supply under tray with in line fuse and that is constantly working key on or off so maybe will have to try this.