Compressor efficiency testing

[offroader]

Can anyone give me the proceedure for basic compressor efficiency testing. We have a batch of air cooled roof top package units and some seem to perform much better than others. I would like to check the operation of the compressors as this is where I think the problem lies.

[Brian_UK]

Why do you think that the compressors are at fault?

[Frikkie]

Do you want to test efficiency or performance of these compressers?