Yes, that is how it is supposed to work. The single battery campers only
supply 12 volts to the fridge element when the engine is running and the
alternator led on the dash is off. This is because the fridge would
drain the battery in only a few hours anyway and leave you stranded.
Also you could forget to turn it off and kill the battery completely and
this could ruin the battery if done repeatedly.

Most people wire up the aux battery with the same protection. Others
want to have just the aux battery able to supply the fridge even when
the engine is off. This is ok if you pay close attention but humans make
mistakes and you will likely be surprised with a dead ax battery
sometimes in this case. I used to do it this way but it caused me grief
once too often.

Mark

Phil Bard wrote:
>
> Excuse my ignorance, but I just may have learned something.  Am I to assume,
> gentlemen, that the 12v power option on the frig only works while the engine is
> running?.....assuming, ofcourse, that I don't have an aux. battery?
>
> ....Phil in Bakersfield
> '85 Westy
>