Hi Guys.

I'm not sure why the GM A6 compressor gets so much 'bad press', they are a very good compressor. As a matter of fact all of these newer so-called 'more efficient' compressors are just a smaller, albeit more modern copy. The A6 & the Sanden are both axial piston style compressors, not rotary style as they are commonly, but incorrectly named.

The main problem is most of the A6s out there are now 30-40 years (plus) old & need an overhaul or at least a re-seal (With R134a compatible seals). In these days of the throw-away society, there are only a few guys around that can do job this properly.

Most A6s have a displacement of 12 cubic inches, compared to the SD508's displacement of 8 cubic inches. So while the SD508 takes 33% less power to be driven, its output is therefore 33% less, so it's not necessarily 'more efficient'.

The Sanden SD508, was originally branded Sankyo when it first appeared in the early 70s. They are no longer made. Its modern equivalent is the Sanden SD7H15, which is the updated version made for R134A. It is a direct bolt-on replacement for the old SD508. The SD508 has 5 pistons, while the SD7H15 has 7 pistons, so it is slightly smoother in operation, but looks near identical.

If originality is not of importance, there is nothing wrong with fitting a Sanden using the adaptor kit mentioned above. It will work out cheaper than doing a proper overhaul on the old A6.

Dr Terry.