reverse A/C 134A back to R12

[dfink]

My car was converted to 134 before I bought it. The A/C is not really very good and does not have barrier hoses. My question is can I dump the 134A and go back to 12 without changing the oil. I assume the oil was changed when it was converted. I happen to have a 30# cylinder of R12 and now none of my cars use it. I guess for what 12 sells for I could probably put new A/C in the car. But will the oil for the 134 work with 12.

[Por_sha911]

There are experts here on the board but it is my understanding that to go back to R12 you will need to flush the lines and put the correct oil in the system. You may want to change out the lines to barrier hose since R12 is expensive to lose.

[scottb]

Hopefully Jim Sims will chime in on exactly what needs to be done to revert back to R12.

My question is this: With R12 so expensive, why would you consider going back to R12 when you don't have barrier hoses? If it were me, I'd replace the hoses and receiver/drier and flush the rest of the system before going back to expensive R12. Otherwise, I'd just keep topping it off with R134 and not waste the very precious and expensive R12.

[Por_sha911]

My reasons: R12 cools better and doesn't leak as quickly in the absence of barrier hose. Also, 134a has been going up in price and the environmental wackos are now saying that it also needs to be going away.

[Jim Sims]

If there is poor performance in the system with R-134a a switch back to R-12 isn't likely to solve the problem(s). Also, a typical R-12 automotive system with traditional non-barrier hose will lose about 12% of its charge per year, a 911 with it's extensive hose will lose even more - using R-12 is not a solution to that problem. That being said, one can only convert back to R-12 without changing the oil if the conversion was done with ester refrigerant oil. If the conversion used conventional PAG oil then the PAG oil will have to be drained and replaced (I would also fully flush the system and replace the receiver/drier). Conventional PAG oil breaks down rather quickly in the presence of chlorides resulting from the interaction of the R-12 and interior metal surfaces of the A/C system. There are "double end capped" PAG oils which will work with R-12 but they are more expensive and the likelihood such an oil was used in past conversion I would judge to be quite small. So unless one knows for sure what the current R-134a refrigerant oil is, conversion back to R-12 is not straight forward.

Yes, systems based on CO2 or even ordinary air as a refrigerants are being considered. The future is coming whether we are ready or not.

[EarlyPorsche]

If CO2 cools I'll take it. Heck if ordinary air cools I'll take it. Not a big price to pay to keep our air clean.

[Motorhead-45]

Originally posted by Por_sha911
My reasons: R12 cools better and doesn't leak as quickly in the absence of barrier hose. Also, 134a has been going up in price and the environmental wackos are now saying that it also needs to be going away.

I posted the following a couple of weeks ago on the price of R-134. The information is still valid. As of last week the case price of R-134a was still $36.00 but the price of the 30lb cylinder had dropped to $89.00. The means the cost of enough R-134a to recharge your 911 is less than $10.00! An $89.00 investment would buy you enough R-134a to last a lifetime...or at least the lifetime of your Porsche!

My original post:

For those of you that service your own a/c systems I'd like to pass along that my local Sam's Club has again lowered the price on R-134 refrigerant. 12 can cases of 12oz R-134 are now $36.74 per case. The 30lb bulk cylinder is just $93.46. These are by far the lowest prices I've seen in a long time. I have no idea what is driving the price down but now might be a good time to stock up! No EPA license required for R-134.

Reason for price drop: The last pour of concrete for the three rivers dam in China was completed. The contractor for the project brought up a large supply of R134a. They were using refrigerant to cool the concrete from getting to "HOT" as it was setting up. There is a large surplus of R134a on the market as a result.

[Motorhead-45]

Originally posted by dfink
I guess for what R12 sells for I could probably put new A/C in the car.

Fleabay prices for a sealed 30lb cylinder of R12 are hovering around $325.00. I'm pretty sure that won't cover the cost of a new A/C system.

[jklaspok]

R-414B is a coolant with claims of greater efficiency than R-12 and R134a. I used it in place of R-12 and it worked great. Unfortunately it leaked out after a few weeks. I since have corrected the leaks and recharged with (free from a friend) R-12. The cost for the R-414B was around $11.00 for a 10 ounce can. From what I read at http://www.icorinternational.com/literature/PDF/HSFS.pdf#search='R414B' , it will work with no AC conversion necessary.

[Jim Sims]

R-414B is a mixture (azeotrope) of R-22, R-124, R-142B and R-600A (isobutane). It is subject to fractionization which will degrade it's performance as a refrigerant. Plus, since it contains R-22 the below applies:

R-22 damages the NBR nitrile or HBNR rubber parts (hoses and seals) used in R-12 and R-134a mobile air conditioning systems. The damage manifests itself as popping, blistering, loss of elasticity (ability to seal) and tendency to dryrot. In addition, R-22 is not compatible with the XH-5 or XH-7 desiccants found in R-12 or R-134a systems; the R-22 causes mechanical breakdown of the desiccant which can then travel downstream and clog the expansion device (valve, orifice tube, etc.). R-22 is intended for use in "hard" plumbed stationary applications with hermetically sealed compressors.

[Por_sha911]

Originally posted by Jim Sims
R-414B is a mixture (azeotrope) of R-22, R-124, R-142B and R-600A (isobutane).

R414b: Isobutane + small leak + spark = search for new car.

Getting back to 134a: without barrier hoses may be cheap but you'll be doing a lot of refilling. How fast is it leaking out? What is your time worth?

[schoward]

Question -- I have a R134 conversion (compressor/dryer) on the old hoses. I generally have it evac, leak tested and charged in the spring and by the fall or the following spring (when i remove it from storage), the charge is gone.

Can i top off during the year using an auto parts store kit or is a full evac always necessary?

I know barrier hoses are the soln, but So far - this hasnt been too much of a hardship and my vent temps can handle 90+ degree days when i do use it (which isnt that often).

[Jim Sims]

You have more than a hose permeation problem - you likely have a damaged hose or leaking hose fitting or A/C system component. Find the leak and get it fixed.

A full evacuation and refill is not necessary provided the system pressure is still above atmospheric, one purges the refrigeration harness lines of air and you haven't lost significant oil - look for dirt stains just not oil as the R-134a refrigerant oils evaporate rather quickly. However the "auto parts store kits" are not adequate for recharging as the proper R-134a charge is determined by both pressure and temperature measurements - the cheap gage on the kits that merely indicates "full" can leave the system over or under filled. A reasonable quality refrigeration harness, a check valve equipped dispensing refrigerant can valve, a couple of bimetallic thermometers and a pair of safety goggles will run around $130 to $140 and you can reuse the gear year after year.

[quattrorunner]

Then again, if the leak is small enough, I feel that the recharge kits from auto parts stores are better than nothing, infact, it made an otherwise nice honda pilot with worm A/C ice cold. Mine cost 40.00 and had the gauge which allows you to know if the pressure is too high or low. Simple and effective. I only used one of the cans too, so now I can recharge it again if need be. It's been 1 year and no need for that

[Jim Sims]

The kit pressure gages are not compensated for temperature; the correct charging pressure ranges for 70F to 110F ambient air temperatures are significantly different. The high/low bands on the kit gages are only approximately correct.

[quattrorunner]

Well, yeah. And it may not work as well for others as it did for me. I could have added that.

[buttjoint]

All this being said, Scotts in anaheim, the porsche ac experts reccomended r12 when they installed a new rotary compressor on my 89.

[quattrorunner]

Jim, A question for you.
I will be doing the A/C on my car this winter or at least before summer. What complete system would you recomend for me at this time? And I do mean complete. I will have an intercooler by that time. The reason I ask is that I have read a couple times tha one of the kits has been having some issues with the compressor lately. It may not be a big deal, but what are your thoughts?

[Zeke]

I have the gauges from years ago, but no temp guauges. Can I add to my "kit" (these are proffessional quality that cost well over $100 20 years ago) to service my own AC?

[Jim Sims]

"I will be doing the A/C on my car this winter or at least before summer. What complete system would you recommend for me at this time? And I do mean complete. I will have an inter-cooler by that time."

This system is to operate in Las Vegas, NV in the summertime?
What do you have now for A/C? OEM with York compressor, deck lid and front valence condensers? Will the inter-cooler displace the deck lid condenser? What are your plans for augmented external oil cooling? If you're adding a turbocharger, the existing kits now offered may not just "bolt up and assemble." You may need to add elements from various kits/vendors and make custom refrigerant hoses. Be aware that SC's have a fundamental A/C "bottleneck" with the poor air distribution through and under the dash. Changes can be made to improve it but it'll still be a limitation.