AC low-side charge port. AKA: I'm going to burn the car down

[GTOger]

Who's bright idea was it to stick the low side port behind the serpentine belt and under a vacuum hose? I'm really angry about it.


The wife brings the car home today and says "oh, the AC isn't working". And it's August in Texas. So naturally I want to help.


There's no helping. Some designer made sure of that.


So here I am, hat in hand, asking for someone to tell me how in the world to maintain that stupid AC system in 2021, where there is R134a and its associated adapters.



Surely I'm not the first person with one of these cars to want the AC to be serviceable.



Have you done a R134a conversion? How do you handle that low-side port?


Something else?



And please, I've seen all the "just stick with R12" comments, which are just not viable or helpful in this day and age.


I need your help, friends. I love tinkering with my hoopties, but this one just seems to be difficult about everything. I blame Lotus.

[Matt B]

Don't worry, it's not that bad. Don't burn you Z, light up a nice cigar and then go and fix it! I just recently did my R-134 conversion. After long evenings spent with investigation I did the following (and I'm pretty confident that it was a good way out of various good alternatives).

- Release the R-12 (was done during import so no work for me)
- Remove the Plenum/throttle body
- remove the A/C compressor
- using a catch pan or bowl flip it over and twist the spindle in both directions to remove all oil though the refrigerant in-/outlets
- Fill it with PAO68 oil. I used MAHLE ACPL 11 000P BEHR. This stuff is compatible with R-12 oil AND dissolves in R-134, so it catches that old oil and makes it circulate in the system. It's a bit hard to tell how much oil to add. Handbook says "30ml more that what was drained". I drained nearly nothing so I added 50ml. Nur sure how many fl oz this is.
- Reinstall the compressor and engine top
- Install the A/C lines using a new R-134 compatible seal (available from e.g. Rockauto)
- Remove the dryer/condenser, you have to drain about 1gallon coolant and remove the water hose that connects the heads and is in you way to do that
- take a new unit (I used AC Delco, proudly made in P.R.C....) and fill it with 150ml PAO68 oil through the refrigerant inlet port
- (this next thing I don't know how to handle in the states, maybe the same) get yourself a set of R-134 adapters. Low side is 1/4" threat (standard), high side seems to be 3/16. There are angled versions which make life easier on low side but not needed to do the job. You may have other chances to access the ports but with these every R-134 shop can service your A/C. High Side is not necessarily needed for the conversion (but probably later for maintenance)
- Screw the low side adapter onto that port of the dryer that points towards the engine. Before you to that remove the valve core from the dryer
- Install the dryer with R-134 compatible O-rings. Torque is specified in the shop manual, but it's rather lightly fastened
- (optional step) remove the valve core from the high side port (next the the passenger side header) and attach the R-134 port adapter
- unplug the low side cutoff switch. It's the one next next to the HVAC unit near the upper coolant surge tank. There is a small screw between the prongs, turn it 1/4 counter clock wise to adjust the cut off pressure for R-134. If there is no screw: wrong switch
- reinstall the plug
- Use an 90? angled r134 service port adapter to connect to the dryer low side port. It barely fits, but it fits. These are quick snap type, so you have to retract the locking ring while prying the adapter onto the port. It's a bit of a PITA but doable. The adapter I used had an internal tap mechanism so it won't immediately open the valve once seated.
- From here it's simple: pull vacuum and evacuate the system for about 2 hours to get all moisture out of the system, stop pump and check if vacuum it held for 5-10 minutes
- fill the system with 800gr (1.78oz) r-134. There is a formula how to convert R-12 to R-134: R-12*0,9-0.25, which translates to 2.25*0.9-0.25=1.775 pounds of R-134.
- Following the manual it's done in 2 steps: 50% with engine running but A/C switched off, then immediately switch A/C on to maximum cool (minimum temp and maximum fan) and add the other 50%.

From here follow the manual, if everything was done correctly your A/C should blow ice cold and hold the R-134 for a while.

The filling process is nicely described in the shop manual, only that modern refrigerant bottles don't need to be flipped over.

I hope I didn't forget a step. For sure I can say that I didn't replace any other parts or O-Rings. I can't tell you for how long this will last, but many have confirmed that they didn't swap out any seals and their systems work for years. I thinks it needs some luck, but a good horse only jumps as high as it has to .

Good luck, hope the above is of help!