Yes, I used the search function, but there is so much info, I'm trying to separate the wheat from the chaff. I'm hoping this will help someone else as well.

The car is a 1991 convertible. It has already been converted to R134.

I know the compressor is leaking. I'd like to take the opportunity to replace it with the lighter Sanden unit from a later model. Is this a straight bolt in, or am I better off finding the larger Harrison A6 that is in there now? If the A6 is the way to go, will any A6 (i.e. from Rock Auto) fit, or is there something I need to look out for?

The reason I'm asking is some posts said "no problem, rear hoses, mounts right in", others said "new mount, new hoses, A6 works fine". I'm trying to find a consensus (I know, good luck there, right?).

I also know I should replace the dryer. While the system is apart, is there anything else I should replace as well?

I'm open to advice, I'd like to keep this as a concise, "best practice" resource. In other words, future "Searchers" can have a one stop place to learn how to replace an AC compressor with minimal stress, and long term future operation. Thanks!

 

Sorry I can't help, but I am interested in the answers you receive.
I've seen kits are available to convert form R12 to R134A, that come with the Sanden compressor, along with other bits that most would say are 'not necessary' when converting to R134: https://www.fenair.co.uk/product-pag...en-upgrade-kit

 

The Sanded is not a drop in. it's shorter, so the mounting brackets are different. There are many variants of Sandens that were used in hundreds of different applications, so there are lots of differences in clutches, mounting points and hose mounting styles and positions.

The major differences in the A6, (again used in many different applications) are metric or SAE threads for the mounting points, different clutches/pullies, different locations of the electrical connections for the clutch and the compressor protection - early versions were a superheat switch, later was a low pressure switch, (this is what your car will have) and some had nothing. You need to match the type of protection. You can swap the end plates of the compressor, but again it depends on where yours is leaking. If the Superheat switch is the culprit, swapping end plates will move the problem to the new compressor. I have also has the end plate gasket leak.

A major problem for the Jaguar A6 that results in leaks is the retaining plate for the hoses. Many mechanics over-tighten the bolt in the center and that bends the plate. It then no longer holds the hoses tight to the endplate and they leak. If you look at 70's GM cars that used the same hose arrangement on the A6, the retaining plate is twice as thick as Jaguar used, and it doesn't bend. I've never had leaks after changing the Jaguar plate to a GM one. Along with new O rings of course.

So perhaps before condemning the compressor, find out exactly where the leak is. The way I do it is to evacuate the system with a vacuum pump. Then I have an adapter to fit the charging hose to my BBQ propane bottle and I put in about 10 psi of propane. Then I have a hydrocarbon gas detector good to 5ppm and simply run the gas detector sniffer probe around each joint and I can usually find the leak quite quickly. If the leak is big enough you can hear 10 psi escaping - I found a pinhole in the condenser than way.