Guys, I have a stock 71 Cuda 340 with factory A/C that stopped working a few years ago (it never really worked all THAT well in the first place, but that's another story...) that I'd like to go through the system and get it working again. I plan to replace all o-rings and seals that are serviceable and have access to an R-12 fitted vacuum/charging station to check integrity when I finish. Should I replace things like the expansion valve, drier, or? while I have it undone? Yes, I know it's clunky, heavy, and all the other negatives typically associated with OE R-12 systems, and could upgrade to a Sanden type compressor, switch to R-134, etc, but I want to keep the car completely stock. Anyone with A/C experience, and or sound advice regarding this... your suggestions would be much appreciated! Thanks guys!

Change the dryer for sure.At the shop when converting to 134 we found some were great some not so good.Id drain and change the oil in the compressor also.Then after seal replacement vacuum it donw.R12 is kind of hard to find now.I have 1 small can left.Most switch to 134 Just beware that some cheap stuff isnt clean has butane etc in some.use 134 if you convert with the sealer in it.Wont stop large leaks but will stop small one.Some will say change all the hoses etc.Unless they are bad we really had no problems with them Flushing the system might help.That and make sure the evap core is clean.Rocky

first I'd wanna find out if there is a leak or not otherwise you'll likely have to go back in there again in short order & redo some items/recharge, not fun (& it is hot out), you need (want) the AC to stay functioning when done the 1st time. there just was a thread & something was mentioned about a particular type (Mopar?) of expansion valve to avoid.

The aged hoses and the compressor seal are common leak points, it'd be wise to replace them and the drier regardless of which refrigerant you use. Having said that, I would stay with R-12 especially since you have access to a service machine.

It took total replacement of all rubber to fix the leaks in my Cuda. I used barrier hose so I could go to R134 in the future if I run out of R12. O rings were all replaced initially and there were still leaks. Again, I used the newer green o rings for 134 in the future.
Changing the drier is mandatory unless you left in Death Valley, it picks up moisture from the air. Evaporator valves are not that expensive so I changed that too.
Craig

I would replace everything. Dryer, Evaporator, Hoses, Seals, Freon sensor. Pressure test the coil and condensor. You only want to do this once.

First test the system for leaks to determine scope of the job. Could be a big job, i.e. eveaporator replacement. Then, check to see if the compressor itself turns freely with no grinding or noise. If good remove old oil and replace with oil compatible with the refrigerant you plan to use. Flush out condenser, and evaporator if original is good. As stated above, replace the drier, all the hoses and orings. Then leak check again to confirm all leaks repaired. Pull vacuum for 2-3 hours to remove any moisture. Make sure your vacuum pump pulls a deep vacuum. The recharge with refrigerant. There are many detailed steps in between in which you should refer to the service manual.
Ron

1. Get a flush kit like this that uses shop air. Buy some A/C flush solvent, and flush the evaporator and its entrance and exit hoses and the condenser and its entrance and exit hoses. It should not be necessary to flush the compressor itself. Add refrigerant oil per shop manual.

2. After replacing all O rings, pull a long vacuum with a good pump like this. Any flush liquid left in the system will be vaporized by the lowered pressure.

3. Leave the system under vacuum for a couple of hours. If the system keeps its vacuum, this should indicate no leak. (Mine leaked at the compressor seals.)

4. Re-charge with R-12 cans, each placed in a pot of hot water. By watching the manifold gauges, you can tell when each can is empty. You may need to jump 12v to the compressor clutch to make it engage on an empty system (if there is a low pressure cut off switch).

5. You can reclaim R-12 from a car system if you have a large Freon canister. Any type of clean, used refrigerant canister will work as long as it has the right threads or thread adapters for your R-12 manifold. Place the canister on its side in an Igloo cooler with dry ice on top of the canister. Open the system to the canister. Takes 1 or 2 days and 1 or 2 batches of dry ice. Around here that would be $15 or $30 of dry ice. When the manifold gauge reads below zero, you're done. It helps if you have a scale so you can weigh the canister to check progress. Or buy a Freon pump for faster reclamation. I've reclaimed R-12 with dry ice several times.

I'm running stock system on R134

I in fact changed the desicant from filter once, but don't bother about, rockauto sells these ready to R134, same as expansion valves already adjusted for it. Just email them to ask about the PN and get it in your cart. I bought it after make the conversion and they are there ready to be installed when my car come back tomthe streets.

Another upgrade will be an aluminium condenser EXACTLY to the original iron piece, got it from ebay.

Thanks guys for all the great advice, links and suggestions! I'll be tearing into things next week and hoping for a relative painless endeavor. Who am I kidding? It'll likely turn into a nightmare!