Old A/C System Recharge
 

Well wouldn't you know it, I have an old A/C system that needs re-charging. I still have three cans of freon, which the old system used. I believe the system used five or six cans. Now-a-days with the CFC eliminations, I am left scratching my head. Is there any freon still out there? Perhaps more appropriately, what needs to be done to my old system to use the new refrigerants. Is this a compressor replacement issue? Would eliminating the system allow more horsepower?
Thanks -O.K.

Yes, authorized dealers still have some of the old R12 freon on hand, albiet it is expensive $30-50 a pound and the system takes 47 oz according to the Bentley manual.
If your AC hoses are still in good shape and your compressor is in good shape it is economical to continue to recharge with the R12 for as long as you can. But remember that R12 depletes the ozone layer so there is an environmental factor to consider.
Given the age of your car '79 the hoses and compressor may be suspect. To change to the R134 newer type coolant you have to change out your hoses and your compressor and reciever dryer - (not 100% sure if you need to change your reciever dryer) - expensive to do the entire system. The R134 is a smaller molecule and will seep through the hose of your original R12 lines. Note the R12 lines do have holes, so eventually you will need to recharge every system.
With regards to the horsepower question you won't get any more horsepower from the engine by removing the AC any different from when you do not have the AC running... ie when you turn on the AC you will notice a slight load on the engine, then when you turn it off the load is released. The AC compressor is belt driven from the engine. However there will be a weight reduction in the total weight of the car, hence most track race cars remove the AC. Another consideration for removing the AC and why I didn't remove it when mine needed recharging is the defrosting and defogging capability in wet weather.
There are many posts so do a search here.
Senior members I'm sure will chime in where I have left gaps as they really have some great knowledge in their posts.
Also there is a website: http://www.griffiths.com/achelp/achelp1.html
Wayne's 101 projects for your porsche gives an overview of the AC system and the Bentley manual helps with troubleshooting and diagnostics.
Cheers
CrS

The best answer is ---- it depends. The original AC system is marginal at best. As long as all of the components are functioning properly then you should be able to get adequate AC by simply adding refrigerant. But it's unlikely. It's also not as simple as just replacing the compressor.

As Coral Red Syd said, you have to evaluate the whole system and determine what it is you want. There are lots of options.

Do a search on Jim Sims or Kuehl who are the experts and you'll find tons of info.

IF you still have pressure in the system, push the Schraeder valve on the low pressure side and see if it hisses a little, then go to WalMart and buy a recharge kit for about $20 its a replacement, but it will sort of work. Get the cans with the PE oil in them if IIRC, look for the replacement charges for R-12 to R-134a, or recharge with your cans of old R-12 and see if it leaks you'll need an A/C recharge set of gauges. The older hoses will leak out freo n, in a summer season. Otherwise, replace with new barrier hoses, which is what I did when I converted to R-134a.

Typically receiver/driers should be replaced whenever the system is opened for servicing. An old R/D designed for R-12 is not compatible with R-134a.

Cans of R-12 are not available "over the counter" to consumers. Do not mix R-12 and R-134a. When converting to R-134a the refrigerant oil must be changed. The system, if still holding pressure, should be taken to shop and any remaining R-12 extracted and recycled. Have them leak check the system. Then begin the conversion process:

Recommendations for good performance and value when converting a 911 from R-12 to R-134a:

- Extract any remaining R-12 refrigerant and recycle.
- Open all lines at low points and drain out mineral oil.
- Flush all condensers (this can be done on the car) and then allow them to fully dry out; again this is to remove the R-12 mineral oil.
- Do not flush the evaporator unless you remove it from the car and remove the expansion valve first. If the evaporator is out, clean the air side of dirt and lint and when reinstalling ensure the the foam air side seals are in good condition.
- Do not attempt to flush a compressor or a receiver/drier.
- Drain the compressor of mineral oil and replace with the appropriate amount of ester oil (POE). Use a fresh unopened bottle of ester oil; buy it in the 8 fluid ounce size bottles (NAPA and AutoZone sell this oil). If no other information is available regarding the amount of oil to add then replace what was drained from the compressor plus a ounce for every other component flushed or changed. For example, if two condensers were flushed and the receiver/drier replaced then add an additional three ounces over what was drained out of the compressor. Excess oil will impede performance as will R-12 system mineral oil left in the condensers.
- Install a new receiver/drier with XH-7 desiccant prior to evacuating the system. Most receiver/driers sold today contain the XH-7 desiccant. Inexpensive receiver/driers (less than $30) may be purchased from NAPA or AutoZone and can be used with some "hose flipping" if your wheel assemblies are not too big. Otherwise one will need the use the slender OEM Behr receiver/drier ($90+).
- Hoses if in good condition do not need to be changed to barrier style unless there is some other problem like a leaking fitting. If one is adding new fittings or components (such as a condenser or compressor) and can change both sides of the fitting convert to the o-ring style whenever possible.
- Replace all fitting o-rings using new HNBR rubber compound (usually colored a light green or blue) o-rings; coat the o-rings with Nylog (HFC compatible, part no. RT201B from Refigeration Technologies) gasket thread sealant and assembly lube. Also use Nylog on the metal to metal sealing surfaces of the flare type hose fittings.
- Install R-134a servicing fittings or adapters to both the high and low side; on some R-12 fittings it is necessary to remove the old Schraeder type valve core.
- Install a high pressure shutoff switch (wired into the compressor) in the high pressure line between the compressor and the first condenser. EPA requires that pro A/C shops do this when making the conversion to R-134a along with a sticker noting the conversion.
- Evacuate the system and leak check; if leak tight then evacuate for three hours using a good two-stage vacuum pump that can at least reach 40 microns of pressure; new dry vacuum pump oil in the pump is helpful as is having the car sit in the hot sun during evacuation.
- Charge the system using refrigeration pressure gages and thermometers) one at dash air vent closest to evaporator and one on the air inlet side of the main condenser) - the sight glass method doesn't work with R-134a. Air must be flowing over the condensers for proper charging - on a 911 have the engine deck lid down and the engine running at 2000 rpm. Do not over charge; converted systems will use less R-134a as compared to the original R-12 charge. Leak check the system at pressure.

If you do not understand these systems nor have the proper equipment seek experienced assistance and the right gear. A/C systems can blind, maim or kill you. Always wear eye protection.

A subcooler may be installed either before or after the receiver/drier in a 911. After the receiver/drier and as close to the evaporator as possible is better but not always feasible.

For improvements in performance I recommend (in order):
Proper conversion, charging and maintenance.
Better and leak tight air flow in dash and evaporator area.
Clean condensers with air moving over them (fans for slow traffic conditions- triplex pressure switched is the ideal).
Subcooler.
Better and more condensers.
Improved evaporators.

Wow! That pretty much answers my questions and questions I didn't even know I had... I appreciate all your inputs. Now it's off to find out just what I have to work with, what leaks and what still works. R-12, or R134a? If I can get it all to work, I'm cool with that...

JIm Sims,
I wish you are here in SCal. I have been any several pro AC shop and none told me that m,uch of a complete list of what they will do. I still remember pepboys told me "Our technician is not stupid" when I told them my AC lines and oil lines are very near the jack point, and asked to stay with my car.

I just removed my AC and for what it's worth, everything was in very good condition visually but there was almost NO refrigerant in it at all - maybe a puff, then silence. I have receipts from the two POs indicating it had been recharged about two dozen times in as many years.
R12 is bad, putting it in your AC system will almost surely just discharge it into the atmosphere. You don't want AL Gore to make ANOTHER movie, do you?
Save up for a new R134 conversion kit, that's what I'm gonna do.

Regards,

Unfortunately, all automotive A/C systems will leak out their refrigerant charge. The many joints and the rotating compressor shaft seal make this inevitable - it is only a matter of how quickly they leak down. The more elastomer hose and joints the faster and more likely they'll leak down. In this regard its hard to envision a worse passenger car system than that used in the 911s. Suburbans or vans equipped with a rear evaporator/blower perhaps? I just helped install a custom high pressure refrigerant line made of aluminum refrigerant tubing along the top of the inside left rear fender and the left rocker in a Carrera (for additional condensing function); it will be interesting to see how this car does in regards to holding the refrigerant charge.

944 S2 Low Side Port???
 

Anyone know how I can find the low pressure side port for the 944 S2? Also, do I need to "jump" the compressor if it's not turning on currently?

I can't currently seem to find any articles that detail the procedure. In the past I read an article that I think indicated that the "low" side is on the top of the compressor. (I think the it is a high pressure one on the side.) The guy who wrote it detailed a major process of removing the alternator, and grinding down the side of the alternator and bracket to allow for easier access in the future. I'm hoping there is a way to do this that is a bit less drawn out.

Thanks in advance for any help!

http://forums.pelicanparts.com/uploa...1178834886.jpg

Oops! Sorry about the big picture. I thought I was loading an image as a signature. Please forgive me, I'm still learning the forum.