If I may jump in, it depends whether you have an R4 “pancake” or A6 (longer) compressor.
The perimeter-design, radial R4 is an inferior design to just about anything: noisy, less efficient, poorly compatible with rebuilding due to how it wears internally. New units, if you get a good one, are okay with the correct oil type/amount and refrigerant charge, blue o-tube, and factory condenser. They would do better with a parallel flow condenser, but I personally prefer the ease of cleaning the factory condensers with the tradeoff of slightly inferior efficiency. I’ve got a Four Seasons/Compressor Works R4 that practically blows ice chunks at you. Delphi-Harrison liquidated their R4 tooling to them so there’s only one source of new units AFAIK, and sometimes they’re lemons out of the box. The rebuilds are frequently lemons out of the box. When my current R4s go, I’m anticipating converting to v-belt Sandens. I’m assuming this is what you currently have. If it’s the factory Harrison unit, I’d also wager it’s at the end of its life even if the miles are low.
You must be registered for see images attach
The A6 is a swashplate, axial design, which the credit goes to Frigidaire on that one, I believe. They’re big and heavy, and they’re more expensive to rebuild. A rebuilt one costs appx. twice a new R4, and a new one costs thrice the same new R4. They don’t have the design faults that make them repel rebuild in the same way that R4s do, and I’d say they’re comparable to the Sandens since they share the same basic design, although I think Sanden makes both swashplate and wobble plate models, and I haven’t done my homework to know which ones are which. I’d like to know what extensive users of both say about how they compare.
You must be registered for see images attach
As a footnote, I’ll add that I’ve posited converting to a Harrison V5 when that unfortunate and likely very hot day comes. It’s also an axial, swashplate compressor, but it’s variable displacement, almost as compact as an R4, and relatively cheap to purchase new production. The real world benefit to the variable displacement part translates to no compressor clutch cycling. It’s either on or off, and the load is gentler on an engine. Cool design IMO.
You must be registered for see images attach