New to the reefer madness

Didn't do any training I come from hauling sticks and pinestraw and dump wagons. I told them I could drive. They showed me how to turn it on and set it. Then asked if I have mechanical knowledge I said yes I've built motors and trannys and rear ends I also work in a lite mechanical diesel shop. They explained it just a very small diesel engine like a tractor with a big AC compressor and condenser. Seemed simple enough. Since the original post I've learned the way the computer is programmed any temp set at 34 and above is continues and below that is cycle to alow auto defrost cycle for my longer 3 or 4 day runs. My load of fish from Homestead to Billings actually scared me when I was walking back up to the truck after eating at some diner in Kansas I saw a huge amount of water coming out of what looked to be drain holes. My first assumption was that the trailer ran out of fuel and spoiled my load I knew I was low but thought I had a few more hours. Another reefer driver had been walking in and explained the unit went through the defrost cycle and the drain lines don't drip like a normal AC unit it has a special cap that lets it build up a certain amount of pressure before expelling the water he then told me to drain that line during me pretrip just like I do my air tanks