From: Wally Plumley [wplumley@bellsouth.net] Sent: Monday, April 02, 2001 11:03 PM To: 928 Subject: [928] Re: r134 At 09:26 PM 4/2/01, Roth, Richard wrote: >My mechanic buddy says that nothing special is needed for a R12 to R134 >conversion; just flush the old oil and load in the R134. ALl this 'nonsense' >about parts compressors etc is just BS > >Somebody give me some ammo to tell him where he is wrong. First, a general statement: A system that is converted from R-12 to R-134a will lose some cooling capacity. In general, he has a good point. In the case of the 928 in specific, he is wrong. The 928 A/C system has a LOT of O-rings. Every joint in every line, every connection - all have O-rings. These black rubber O-rings are ten to twenty years old for most of us. They are hard, brittle, and already leak with R-12. If you put R-134a in there, with its smaller molecules, leaks are assured. The receiver/dryer will contain enough old oil to cause a problem, and if the system will be open for a couple of hours to change the O-rings, a new receiver/dryer is mandatory. In my opinion, a minimal change from R-12 to R-134a includes: Leak test the system while it has R-12 in it - repair all leaks. Change all (or almost all) O-rings. (This will help with the leaks above.) Empty the oil from the compressor, flush it if possible. Put fresh oil in. PAG (polyalkylene glycol) is better oil, but isn't compatible with the mineral oil that is in the R-12 system. POE (polyol ester) oil is compatible both with the mineral oil/R-12, and the R-134a, so it is normally the best choice for a change-over. Install the same amount as what was drained out. Blow the oil out of the condenser, flush it if possible, checking for free flow. Add 2 ounces of new oil. Install a new receiver/dryer. Install the new charging fittings for the R-134a. Evacuate the system to a hard vacuum, using a good vacuum pump. Leave pumped down at least two hours. Charge the system with R-134a, using approximately 80% of the amount of R-12 specified. In my opinion, R-12 is better, but more expensive. No matter which of these two refrigerants you use, the condition of the system is the main thing that determines how cool you are. Wally Plumley 928 Specialists From: Dr. Bob [dr.bobf@worldnet.att.net] Sent: Monday, June 25, 2001 2:34 PM To: 928oc@list.928oc.org Cc: Chuck Klingenstein Subject: [928OC] re: Air Conditioning Chuck Klingenstein wrote to the list: > >I have reached a point where it is time to upgrade my AC to the newer R134a >since my R12 system is dying. Does anyone have a good experience to share >with me doing this conversion? Cost? Parts? > >Chuck >1988 stock 928 with 5 speed > Hi Chuck: First thing of course is the reason you are upgrading. If it's only because of leaks, it's a good thing. I restored my '89 S4 to a relatively leak-free state and did the conversion to 134a with excellent results. Parts you'll want: -- a complete o-ring kit. Dave Roberts at 928 Specialists put a kit together for me that included almost all the o-rings I needed. There are a couple that were not listed, on the compressor manifolds, and they came from a local AC shop for a few dollars. -- Replacement hoses, a couple of them, in the new barrier style for the R-134a gas. Seems the 134a molecules are smaller, and will leak out faster through the old style hoses. 928 International and 928 Specialists both list the hoses. Another source is Charlie Griffith at www.griffiths.com. My local specialty AC shop made mine for me. -- A replacement receiver-drier. 928 Specialists has one that's shown as an OEM replacement, a lot less than a factory piece, but slightly smaller in diameter and little taller than what was in there. I added a shim in the bracket, and added a little spiral wire loom stuff around the lines underneath to get mine in there nicely. -- Not mandatory but a good idea is replacement expansion valves. 2 Required if you have rear air. -- A few bottles of Polyolester refrigerant oil. Get the plastic bottles, not the stuff in the metal cans mixed with R-134a. You'll want to drain, fill, flush, drain, fill, flush the old oil from the compressor before adding new oil. These are less than $10/bottle last time I looked. -- The conversion instruction from PCNA says that you'll need about 40 ounces (by weight) of R-134a for your conversion. I used a little less than that with excellent results. The little cans are not as good as the big bottle, since you risk air intrusion when you swap the connections from can to can. you can vacuum the hose between the manifold and the bottle before introducing gas, but can't betwwen those little cans. It's hard to justify a big bottle of R-134a for just one car project though. -- Charge port adapters that allow the connection of the R-134a style charge hoses. These adapters are common parts at most any auto parts store. Be sure to pull the schrader valves out of the existing ports before you install the conversion ports. The blue low pressure port is installed on the fitting under the right (passenger side on US cars) ignition coil on your S4. You'll need to have a few basic tools to make your project possible. Some are expensive to the point where they may not be practical. -- A set of gauges and charging hoses specific to R-134a. Less that $100 most places. -- A good thermometer (or two) to measure air temps both ambient and from the center vent discharge. I buy the digital recording type from the kitchen store, the one that stores min and max as well as displaying the current reading. The temps and pressures play together when you watch gauges to determine system performance. Less than $15 each. -- A good vacuum pump. The pump is used to evacuate any air in the system prior to charging. It also causes any moisture that might have accumulated in the system to be evaporated and purged under the vacuum. The more air and moisture you can suck out, the better your system will cool the car. In spite of what you may have read, it is not possible to get good AC performance without evacuating the system before charging. Borrow or rent this, or spend $100-250 on a decent refrigeratoin-grade pump. -- A good leak detector. I went to my local wholesale appliance parts store and found one for about $100, including a spare detector head. Some folks and techs will try to sell you on the idea of using the dye injection method, but since so many of the fittings are out of sight when installed, it takes a catastrophic leak to get enough dye where you can see it. Those connections on the top of the compressor when installed are a shining example. The electronic type detector units have a sensor head on the end of a gooseneck probe, something you can bend and poke in to those tight places. Dye and a blacklight are not the answer obviously. You'll want a collection of basic hand tools, a fitting wrench big enough to remove the suction line connection just behind the radiator, some wire ties, stuff like that. Find a book on auto refrigeration, and read it. Problems creep up, and an understanding of the system dynamics will help you through those problems. The factory manual sections on the HVAC are specific to the car. They show parts and pieces that are specific, and assume that the technician has existing knowledge of the rather generic bits of the system. Good to have this stuff handy. A clean engine bay and a clean workplace are requirements. The tiniest bit of dirt or debris dropped in to where it can get into a line will drop your system in its tracks. Lint-free towels, plastic bags with tie-wraps and rubber bands to close exposed hose ends, etc, all help to keep the system clean and dry while you are mucking around under the engine. I wear plastic painters gloves, and wash my hands frequently just to be sure. An engine bay wash with detergent and water in advance of the surgury is a good idea; use some engine cleaner if you have heavy deposits. The area above the compressor will prove to be a repository for any oil that's been leaking out of the pan gasket, mixed with any sand and road slime and junk that sucks up behind or through the radiator. Spend some extra minutes in that area with the hose before you take anything apart. Dry everything thoroughly before any connections are disturbed. Note the position of the clutch wire connector, the wire routing to it, and how it needs to be tied up to eliminate flexing and abrasion with the drive belts. Mark the positions of the compressor and air pumps on their respective belt tensioners. If you are keeping the old belts, put the pumps back where you found them. Might not be a bad time to replace all the belts if they are more than five years old. Just a couple more to buy and install while you have that stuff apart anyway. No petroleum oils/fluids can get anywhere near your hoses or o-rings, by the way. Use the refrigerant oil you bought to lubricate the o-rings, no other. Keep in mind that a conversion to 134a will not restore any existing mechanical or control problems with your AC system. A compressor failure, for instance, requires a whole pile of cleaning and flushing to get debris out before you ever consider a gas change. If your leaks are from rock damage to the condenser, now's the time to replace. Moisture gathered inside the bottom of the evaporator in a system left open to atmosphere will create an acid that will eventually eat through the aluminum. Both require component replacement at some significant expense. I have a picture article kinda in the works that shows step-by-step what needs to be done to do the conversion. Not quite ready for prime time, (ok not even close...) and I'm not in a position now to work on it. Eventually (maybe over the winter) I'll get it together and make it available to the OC. The www.griffiths.com website has some great info, plus links to various sites and organizations with plenty of other stuff you'll want to read. Charlie offers the conversion parts, replacement compressors, o-rings, hoses and the like that you might need. Last but not least, there are legal considerations to keep in mind, especially regarding venting/recovery of the old gas. This recovery is a job best left to a pro. My local AC guy does this for a very nominal fee, and it beats polluting. He's also set up to do the evacuate, charge, and leak test for a (phe)nominal fee if you only want to do the mechanical part of the work. You may have a similar resource available local to you. I spent about a day and a maybe a half total time on the conversion, working alone but knowing roughly what I was doing. That included time for picture setups, but doesn't include having the vacuum pump on there for a whole day to get every last bit of moisture and air out. The system now cools the car down with a vent temp of 21f(!) with the freeze switch disabled. This will freeze your fingers on the wheel, and has proven more than adequate in my black car in Los Angeles. With the freeze switch adjusted correctly, it cycles between 37f and 41f, still almost uncomfortably cold. The service manuals give a performance curve for the GTS cars with R-134a, and that is a very good indication of what to expect if your system is mechanically sound. Note the dip in evaporator temp at 92f ambient, and you'll appreciate the system performance improvement over R-12 at the same point. 928 Owners in the Los Angeles area who are thinking of the conversion are welcome to access to tools specific to the job. The gas sniffer is available for rent with a suitable deposit to anyone who might need it. Contact me off list for details. Hope this helps! dr bob From: gak@klanderman.net Sent: Monday, June 11, 2001 10:55 PM To: 928 Subject: [928] Re: update on A/C conversion to r134a Hi Jason, Figured I'd copy the list as others may be interested... The parts cost me $200 from 928 Specialists: - O rings front and rear, about $40. - receiver/drier $93 (I think the OEM is only like $17 but has to be shimmed as the size is slightly thinner) - two expansion valves $30 each (not necessary for conversion but cheap so what the heck... only one if no rear A/C). Plus maybe $15 at Autozone for two bottles of POE (ester) oil and the conversion adapters (I used the angle one on the low side and the straight one on the high side). Swapping out all this stuff took me about two days, but that includes doing some other stuff (incl. heater valve) and a couple trips to the store for tools, parts etc. I could probably do it a lot faster the second time. I had a real tough time getting the compressor back in, that alone took a few hours. And I didn't have all the right O-rings the first time so had to order some more. See my earlier post for a catalog of O-ring sizes and locations, though your car may differ... (I can resend if you missed it). Having it filled was $214, including $40 for the R134a (cheaper from autozone), leak finder dye, and 1.7 hours labor (including some general inspection of the car). Stuff that I removed was: the trim around the rear A/C, the passenger seat, the A/C compressor, the drier and fittings around it, the air cleaner and lower housing. Nothing too major really. greg 88 S4 From: Chuck Bos [cbos@erols.com] Sent: Tuesday, June 26, 2001 3:44 PM To: Wally Plumley; Dr. Bob; 928oc@list.928oc.org Cc: Chuck Klingenstein Subject: RE: [928OC] re: Air Conditioning Folks converting their 928's from R12 to R134a- I just checked all the technical bulletins from Porsche listed in the IMACA* conversion manual, and the quantity of R134a suggested for all 928 models from 1983 through 1991 is 860 grams for the single evap systems, and 1030 grams for the dual systems. Note sure why the earlier models were not included. This converts to: 860 grams - 30.34 ounces - 1.90 lbs 1030 grams - 36.66 ounces - 2.27 lbs I'm not sure how accurate these quantities have proven to be in the field, but my single 88 seems happy with just under 2 lbs, the suggested quantity. As mentioned many times previously, the R134a systems are very sensitive to too little or too much refrigerant so an accurate scale is necessary when adding the refrigerant. (* International Mobile Air Conditioning Association, professional trade organization for mobile AC technicians.) HTH Chuck Bos 1988 928 S4 5-Speed Black/black 115K R134a 1987 928 S4 Auto Indischrot/tan 105K R12