Electric cycle for fridge is 110V and takes lots of power to heat fluid for cooling cycle.. Some have 3 cycles (110V AC, Propane and 12V) and if you had 12V
operation it would work while driving, but puts heavy load on battery and alternator, and could deaden battery if you stop for a long meal or side trip..
Propane test is usualy done with mix of liquid dish soap and water to facilitate bubbles, and check all the way around hoses and connections beyond tank valve and regulator.. Use your nose as well, since sometimes it just smells like propane, even if you can't see bubbles, and that shold be presumed to be a leak.. (If it's been immobile for a long time, you may need to have propane tank valves replaced and tanks tested -round valve knobs are bad.. triangular shaped ones are good..). Hoses do get brittle and then flex once too often and then leak.. (ask me how I know...)
Some folks do drive with fridge running on propane.. Use search tab above (type in refrigerator or fridge and driving and propane and see what you get) to find threads from members who routinely do it, never do it, think it's OK and think it's stupid.. Only general conclusion is that if you crash, having open propane line and fire in burner unit of refrigerator is likely going to make the crash incrementally worse.. Pretty much everyone agrees you should stop short of pulling into gas stations and shut unit off, and then turn back on after safely leaving gas station, however...
If tank is aluminum (rather than rusty steel) it is real valuable, so don't let it get away.. You may have to search to find someone to replace valve properly..
>> And often refrigerators take a while to get to operating temps.. Not llike home models that are cold after 15 minutes.. You should also have circulating fan gizmo inside to move air around and keep temps relatively constant..