Small engine to run auto A/C unit

[JohnR]

Sure, why not. If your tinkering with working spare/junk parts, why not give it a whirl? To make it work at all let alone efficiently, you need some serious learning about the refrigeration cycle. You can be in school for a while to master the intricacies. John

[Greg]

If you use all of the parts from a properly designed system most of the hard work is done for you. The advantage of a car system is it is designed to run off hoses.