I used to install under-dash units back in the early 1960's when my father's shop had a distributorship for Mark IV and later, Climatic Air add-on units. One of our customers claimed his under-dash unit would chill beer to the point it had ice crystals in it, while driving across the Arizona desert. However, he made his living as a salesman- - - -draw your own conclusions!
An under-dash unit should cool down a pickup cab to the point of being uncomfortable if it's installed and charged properly.
Jerry
