another quick A/C quick (i hope)

[mark '87 930]

How do I know the system (the clutch in the compressor I guess) is turned on?

When I turn it on, what should I hear. The engine RPM's drop a little and the blowers come on... does the RPM dropping mean the compressor is active?

[rick-l]

You could look at the center hub on the compressor. A magnetic clutch pulls it in.

The Porsche engineers in their infinite wisdom elected not to install a $3 low pressure cutout switch in these high end cars so if it doesn't cool I wouldn't run it.

[mark '87 930]

Thanks... My wife turned it on for me.. and she is a working..the AC that is.

[mark '87 930]

filled 'er up with red tek (www.redtek.ca/) pro sealer as I am sure there was a leak on one of the lines (it was cheap).. and now the little yellow ball is floating again...There are abotu 2oz of refrigerant with the sealer.

You guys weren;t kidding, now she's blow cooler air, and I use the term 'cooler' lightly... These AC systems are a de-humidifier at best!

I might try my luck with the propane/isobutane mix (I don't want this thread to snowball into any controvery now!).

[rfuerst911sc]

Mark you didn't say in your post what refrigerant you are currently useing. I assume it is R12, if it is converting over to propane/isobutane will not increase cooling efficiency on its own. If you are looking for better AC performance components have to be replaced. Generally you have to add condensors or use better condensors, maybe a Pro Cooler to get good performance. I did convert to propan e/iso cocktail but I also replaced all the rubber hoses, added a underbelly condensor and a fan assisted condensor in the drivers side rear quarter panel behind the tire. I removed the engine lid condensor but kept the front condensor so qty 3 total. Works very good.

[mark '87 930]

I am actually at r134, so I just added some. I thought the properties of propane would allow for better cooling, but I guess not. Are you experiencing much better cooling with your mods? I'm not sure I want to go with that extra effort for the few days a year I need it up here.

Good info though, after all the reading I did, I thought I'd try this stuff and then maybe go to propane, but that looks like a semi lost cause!

[Brian 162]

Mark, try Parts Source. They sell 134a or an R-12 blend.

[mark '87 930]

Brian 162, that's exactly what I did (cost me $42 for the two cans -one leak stop and one pro seal..that's what the manufacturer recommended). I think I should buy the gauges if I add any more refigerant though... I can then get a better idea of how close I'm getting to the required specs.. also, it will tell me if a valve or something else is faulty.

As I mentioned, the system does work I just took it out for a spin, it's just not anywhere near my daily driver.

[ruf-porsche]

Best way to add refrigerant to a system is to remove the old refrigerant, pull a vacuum and then add the correct amount of refrigerant

[Brian 162]

Mark, FWIW I replaced all my hoses, repaired leaks in both condensors, and in evaporator, replaced compressor oil, and weighed in new refrigerant, and the system still isn't that great. A/C in a 911 is an after thought in my opinion.

Brian

[rcecale]

Originally posted by ruf-porsche
Best way to add refrigerant to a system is to remove the old refrigerant, pull a vacuum and then add the correct amount of refrigerant

What exactly is "the correct amount of refrigerant?" Is there a specific capacity?

Local A/C place charges $35.00 for the act of "servicing" along with a price tag of $60.00 per pound of R12.

I just don't want to pay for 10 Lbs, if the system only has a capacity for 2...know what I mean? Not that these guys aren't reputable, I just don't wanna look like a bigger goon than I really am.

Randy

[Jim Sims]

1350 grams or about 3 lbs.

[rcecale]

Thanks, Jim!

Randy

[kuehl]

LEAK SEALERS?

There are pro's and con's with "leak sealers" in refrigerant applications and the final word is not quite out just yet.

Some referigerant "Leak sealers" claim:
"They work by swelling the rubber in these components to close the holes." or they "Rejuvenate the seals, gaskets and o-rings in the A/C system."

Frankly "swelling" is not what you always want to correct a leak, or should we say put a band-aid on a leak. Maybe in a refrigerant hose line's inner diameter or a hose line with a small pin hole or crack. But swelling of an o-ring, say a static design for hose connections or the o-rings used in the shaft seal assembly, or any contact elastomer is not always beneficial. O-rings and seal profiles are designed to fill a void or "designed" configuration between two or more surfaces.
Part of the design to fill the void includes the durometer (hardness) of the material (elastomer) to withstand a pressure threshold. Should the durometer shift to a "softer" state then you will get "extrusion" (the elastomer squeezes out between the mating surfaces) or "Nibbling" (the elastomer shears and tears off). These problems, related to changing the composition or durometer of the elastomer are often found with power steering fluid seal revitalizers.

And some sealants claim they are:
"a blend of chemicals designed to seal leaks in both the metal and rubber parts of an air conditioner." I have yet to see any scientific study that could prove any chemical could magically repair and replace corroded steel, bronze, or aluminum.

So, do they work?:
Yes they "may" work, as a band-aid, in certain situations (under certain pressures and limited to certain crack or holes sizes. And they are "cheap" (not meaning cost effective) as compared to a new evaporator, compressor or barrier hose set.

Are they good for the vehicle's overall system?:
Here is the smoking gun! Like second hand smoke, though the nicotine temporarily satisfys a craving, the components of the "smoke" slowly kill the audience and bystanders (compressor, expansion valve, solenoids and your service technician's refrigerant recovery machine).
Not too long ago MAC or the Mobile Air Conditioning Society (a group manufacturers, distributors and repair shops; and yes there is always political interests when you have more than one person involved) prepared very convincing evidence (facts) that leak sealers maybe doing more harm than good. Though the sealants were able to "seal' small leaks, they were also gumming up compressors, expansion valves, driers and solenoids. And, moving further down the stream, the sealants were doing the same job on your a/c technicians refrigerant recovery machine...... to such an extent that a new sector in the a/c industry developed which now markets specialized equipment(s) which attempts to identify whether a leak sealant is present in the system and equipment which attempts to flush and clean out the sealant. So, has the potential issue been resolved? Yeah, but you will have to pay the price when it is needed and used!

Do the manufacturers of these "sealants" warranty their product against potential damages to your vehicle's ac components?
Yes and No. Believe it or not one manufacturer will reimburse you up to $1000.00 for parts, but not labor . Naturally "only trained and qualified technicians" can install the product if you wanted a warranty. And, should the manufacturer find "other fault" for failure then the warranty is void. Sounds fair, right?
Well not really. The limited warranty is only for 12 months.
So if your system gums up within twelve months and you happen to figure out why, then maybe you gotta case within 12 months. The other side of this warranty problem is the labor issue. For example, assume you used this sealant in a 911 and the evaporator core clogged up.
Figuring a shop estimate in labor to evacuate, R&R the evap, vacuum charge and test and you could be looking at up to 6 hours x $90.00 hour, plus $150.00 in refrigerant and supplies. That's nearly $690.00. Granted though $540.00 is what you would have spent in labor anyway if you simply replaced the leaking evaporator in the first place right? No. See when you "knew" you had an evaporator leak you would have had to evacuate out any remaining refrigerant (going by the legal book here). That would have cost $xx.. Then you would have R&R'd the evaporator. Then you would have had the system evacuated and recharged at $xxx.. Done deal! But instead you had to do the procedures twice when you used the stop leak. Given a 964 you can double or triple the labor costs to R&R its well buried evaporator box.
The savvy thing to do before you use or buy a refrigerant sealant is to read the warranty statement, and consult the a/c technician you use.

Do the manufacturers of these "sealants" warranty their product against potential damages to the repair shops recovery equipment?
I don't know all their positions on this topic but we can recite what one well know leak sealant manufacturer had to say about what happens when a repair shop services your vehicle which contains (if they were aware of it) refrigerant with a sealant in it: They say "It is removed from the a/c or refrigerant system with the refrigerant and carried through the recovery machine to the recovery tank. The refrigerant must be reclaimed as contaminated refrigerant. The key word (we underlined, they don't) here is "contaminated". What this means is that the repair shop must have a dedicated piece of equipment strictly used for "know" contamination. Frankly very few repair shops do. And if you find a shop with equipment that will identify sealtants in refrigerant and that has dedicated equipment for contaminated refrigerants then chances are you are going to pay high prices to get the job done right. What is worse in this scenario is whether or not the shop "knows" you have brought them a car with a sealant in the system. If they don't know and you have not made them aware of the fact they could damage their recovery equipment unknowingly. And, since the "contract" or warranty is between you and the sealant company, what is the shop's recourse? Trouble in dodge city my friend.

Yeah, but "I", "he", "they" or "she" used the stuff in my/their system and it works great! Not a problem. What kinda smoke are you blowing here?
Second hand smoke! It is perfectly normal to play the cost game with repairs: "This cost that much and I can do it for this much. So there!" We do it all day long, 24/7. Whether it is working on our cars, taking a vacation or using the lowest priced octane (when we know it pings).
Buy cheap rotors and watch them warp. Book the cheapest travel tour and sleep with bed bugs. Pump that cheap octane in that puppy and watch those pistons melt down and crack.
The potential problems with using band-aid cures develop somewhere between our want for "cheap and quick" and the retailer's (big box auto supply chains) ambition to move inventory. I'm not saying it is the marketing or advertising portion of moving products but rather the need for a quick and seemingly painless solution... or simply taking the short cut.

Further information on the pitfalls of "sealtants for refrigerants" can be found in past publications of MAC and a at this current URL:
http://www.findarticles.com/p/articles/mi_qa3828/is_200304/ai_n9171878