DIY 134 conversion in SC complete!

[Tim Hancock]

I have seen some other recent posts on AC systems, so I thought I would post my some of what I did last week.

My '79 SC with stock York compressor did not work and the PO claimed that he thought it worked about 5 yrs ago (whatever!).

My clutch worked but there was absolutely no pressure in the system. After reading many posts and talking to friends with AC knowledge, I decided to attempt a 134 conversion.

First I ordered a new drier from a local Advance Auto Parts for $18.83 (it ended up having the proper male 45 deg 3/8 flare fittings but they were oriented wrong so I purchased a couple fittings and fashioned an alum 180 deg aluminum tube to allow it to work).

Next I rigged up my homemade CIS tester to attached to the male
flared fittings on the service valves and pressure tested the system. I found a gross leak on the low pressure hose near the jack point (the bad spot matched my partially smashed oil lines, imagine that!). I made a splice with 1/2 brass hose barbs and wide hose clamps. Next I sprayed all fittings with soapy water to look for additional leaks and found none.

I happened to notice that the port on the York (top) that was marked discharge had the low pressure (big) line attached. Obviously the PO's hack mechanic had disconnected the lines at a previous engine drop and reattached wrong. I reattached correctly. Only the low adapter that came with the kit fit my blow port. Note there are no shrader valves on a '79 SC. You have to crack open the service valve to check pressure or add freon. Turn clockwise a couple turns to charge, then CCW to shut off service port to change 134 cans then repeat.

Next I borrowed a vacuum pump and evacuated the sytem for several hours. Next I added the three cans of 134 and 1 can of 134/oil mix following the directions that came w/ the kit. (these kits are sold at all chain auto places for 30-45 bucks)

On a 88 degree day I am getting 45 degrees at my air vent.
I live in Ohio and the summer temps rarely top 85-90 so I am very happy thus far. Hopefully th system stays charged, if not I will inject dye and fix any additional leaks.

I got the "extra" 134 coversion kit from a friend so about $25 for a drier and fittings and a couple evenings of troubleshooting and I have IMO, great AC. I couldnt be happier! (or cooler)

[Early_S_Man]

Tim,

How did you rinse/flush the system?

Did you drain the old oil from the York compressor???

IIRC, the York needs new ester oil in the sump ... not just circulating about like the swash-plate compressor systems in most cars these days, i.e., Sanden/Seiko type compressor.

[Paulporsche]

Do you have barrier hoses?

[Tim Hancock]

I do not know what style of hoses came stock on the 79 SC, but the one I cut and spliced had about a 3/16 wall black rubber tube surrounded by a ss braid surrounded by a cloth type cover. I had to use a die grinder/thin disk to cut the bad section out. If I have to add a 1-2 cans of 134 a year I do not mind.

I have a friend who has done this same procedure on other 911's and has not noted any problems. I considered draining the pump, but in the end I decided against it. Warren, what is your basis for saying that I have to change the oil in a "York" type compressor? Does the oil not travel thru the system the same way as other compressors?

I have heard a lot of myths concerning AC and in the past I have always taken my cars in for AC service. My last car that needed work, 1992 BMW 325i got recharged with 134 (was r12) and has been blowing cold for 3 yrs and has all original hoses, pump etc. and 245,000 miles on it. I was worried about doing this as I had read all kinds of stuff about how I needed to flush and replace hoses, o-rings etc. The place I took it to just changed the fittings and I supplied them with a new drier and that was it.

Oh well, time will tell I guess. Worst case, I will have to buy a different pump and fab up a mount bracket and come up with some fittings. Not a big deal I guess. But man is it nice now!

[cmonref]

Regarding Warren's question about your oil:

If your system was charged with the original R-12, it used mineral oil in the A/C system. You are right -- the oil mixes with the R-12 and is carried around the system, lubricating the compressor in the process.

But 134a and mineral oil are not compatable, and the 134 will not carry the mineral oil around. The compressor will not receive regular lubrication, with predictable results.

Conversion from R-12 to R-134 requires changing the drier, flushing the system to remove the mineral oil, and using ester oil.

[Tim Hancock]

The kit retro kit I used, had (1) can of ester oil (I think it was 8 oz) included which I added.
The kit claimed the ester oil would travel thru the system satisfactorily, while any remaining R12 oil would not cause any thing detrimental to happen.

Time will tell (it has worked fine in my Bimmer thus far after 3 yrs).
I have read in the past that hoses made for R12 should not work for 134,
but since then I have read that the oil in the original R12 system over the years, impregnates the rubber hoses and when converting to 134, the hoses that when new would not work for 134, actually work now.

In theory, I do not disagree with you guys that are advising to flush, change hoses and change compressor styles. I have spent about 7k on this car since I bought it and it is getting close to being sorted out now.
No way am I going to blow 2K on all new hoses, compressor etc etc just to have air that is a few degrees colder. If I have a leak, I will find it and fix it. If my 26 yr old York gives up the ghost, I will replace it w/ a modern rotary compressor. If I find that my hoses leak more than I can
live with, I will purchase bulk AC hose and replumb the whole system.

If my $25.00 "fix and retro" that I just did, continues to work, I will have a big smile on my face.

[cmonref]

Hard to argue with your approach!! Good luck!

[herman maire]

Im about to convert over to the r134 gas on my 5 series.
a few questions
Did you have the system flushed and did you change the oil in the compressor.

Do you think it would be okay if I just flushed the system and put in a new drier, and left the compressor oil alone.

Does this make any sense or does the r134 oil/gas lube the compressor and there is'nt even oil in the compressor.

let me know
thanks

[Tim Hancock]

herman,

DISCLAIMER:
What I did is regarded by some as the wrong way, but my 3 series BMW was just evacuated, new drier, then recharged w/ 134 along with a shot of ester oil. This was done by a local auto shop and they did not mechanically drain anything (only evacuated refrigerant from system w/ vacuum).

I can't tell you what is best, but I did not drain my mineral oil in my 911 but some of it had gone bye bye thru my gross low pressure hose leak and whatever was still in my old drier. After repairing my hose and replacing my drier, I pulled a vacuum with a vacuum pump for several hours then installed the 134 and ester oil that came with my 134 conversion kit. So far so good.

[mtelliott]

Thanks for the write-up. Now we just need the long term test to occur.

Anyone know how much it would cost just to replace all hoses? My AC has been dis-installed for over 5 years and the hoses running underneath look rotted and cracked. For me, I think it would make sense to replace the hoses and then follow Tim's advice and put in a new dryer and see what happens.

Michael

[greglepore]

I agree w/ Tim that older non-barrier hoses do in fact work-my Carrera was converted to 134 a couple years back by a shop on the the cheap (added a procooler as well) and it works fine-I add maybe a half can or so of 134 at the start of each season, no biggie.

[Tim Hancock]

The low pressure hose running on the right side was super tough and unless you snagged it or smashed it w/ the edges of a floor jack cup (like I found mine) I would find it hard to believe that that hose would go bad (it had about 3/16" wall thickness surrounded by a ss braid surrounded by a cloth braid).

[yasir]

I was told even 134 would be obsolete in 1-3 years,so what's next ? It seems like i might have to make the switch in my C2 Turbo as well but i need to know what to switch to ?

[Tim Hancock]

I heard freeze 12 or something like that works good also, but a 134 fill-up from empty (3-4) cans at $10.00 a can at the present time is a simple choice (hell, I got mine free, even easier choice!). If it goes obsolete in a few years, I'll buy a new $20.00 drier, evacuate and put something else in it.

[Tim Hancock]

Update on above described DIY 134 conversion/repair with 26 yr old stock York compressor:

It has been 4 wks since I did this and all is well (no black death or whatever it is called). My vent temps while moving down the road on 95 degree days is holding at 45 degrees. I have driven 80 miles round trip nearly every day with 85-95 degree temps (why is it so f'ing hot in Ohio in June?!?) The first few miles on the way home are stop and go and it IS warm in the car until I get to the highway at which point the car cools down quickly and after about ten miles, I have to back down on the AC controls.

Just thought I would give a real world update for anyone else contemplating doing the same.

[anthony]

I'm on the verge of doing my A/C as well. A couple notes:

You can get a Sanden compressor to replace the York for $100-200 on ebay. A York to Sanden bracket goes for $25-40 or you could easily make your own if you are handy with welding.

If you need new lines, one can buy the crimping tool, new barrier hose, and connectors for less than $250.

[Tim Hancock]

Presently, I see no reason to replace the York as I am very happy with how the system works at the moment. If it goes south, like many say it will, I will probably replace w/ something more modern. So far it is the best $25.00 I have spent on the car!

[rick-l]

I am thinking of the conversion to 134.

How do you get the oil out of the system? Can you just dump it out the connections to the compressor? Is the rest of the oil in the drier?

When you say flush it what does that mean? Seems like you would have to remove the expansion valve to run solvent through it.

[ruf-porsche]

Originally posted by Tim Hancock
I do not know what style of hoses came stock on the 79 SC, but the one I cut and spliced had about a 3/16 wall black rubber tube surrounded by a ss braid surrounded by a cloth type cover. I had to use a die grinder/thin disk to cut the bad section out.

I hope you clean out any debris that may have gotten into the hose during the die grinding operations. A/C System don't take kindly to any type of dirt in the system, the orfice of the expansion valve can become clogged and the system won't operate as it was designed to.

I would have use a hydraulic shear or a ratcheting shear from SEARS to cut the line instead of using a die grinder. No debris to get into the hose and worry about clogging the system.

[Tim Hancock]

I did indeed swab the cut hose ends.

Excellant write up Jim.