'79 911 SC - Should I go back to R12 refrigerant?

[white99c2]

Getting things sorted out with the car, it is running great again. Now on to the AC, I pulled the front condenser, ordered a new motor from our host, and finally got the fan off of the motor. It will be delivered on Tuesday, I hope it helps.
The high pitched screaming howl I am hearing from my system turns out to be the expansion valve. My thinking is as long as I have to this repaired and the system will have to be evacuate should I have it flushed as well, replace the fittings and recharged with R12.
All of the original components are on the car, it works good at night and just doesn't like 109 degree days here in Scottsdale, AZ.
Will R12 help make it colder so I can drive this car when the sun is out?

[x98boardwell]

R12 is suppose to cool better but I have had other people say their R134 is also just as good. I think in our (old) cars the R12 works better with our system due to the heat that the compressor sees and the pressure at which the system runs when hot. The R134 runs at a higher pressure which in the Phoenix summer heat can spell disaster for our systems.

I happen to have 2 14.1 ounce cans of R12 that I found in my neighbors garage. This is just shy of what our systems hold when stock. I took a few pics a few days ago and have not put them up for sale yet. I have no idea what they would be worth but they are in good shape and comes with the introducer line for the cans. I told my neighbor that I would see help him get rid of them.

Best of luck,
Bryan

[Kemo]

i have "heard" that R12 molecules are bigger than 134 and the 134 will leak unless new A/C lines are installed...

should this go in the Rumour and Myth post?

[Scott R]

Given the cost of R12, it's only a good idea if you replace your hoses with new barrier lines. It's just not economical anymore to let the old hoses seep out r12, and then to top it off each year. Our host sells some really great hose kits that are plug and play.

[Tyson Schmidt]

I'd upgrade your evaporator while you're at it.

Either a good used '86 and newer factory unit, which requires the smuggler's box cover with the bulge in it to clear the fan motor, or one of the aftermarket units that are more efficient.

[white99c2]

If all of the pieces of the puzzle are working properly including the front condenser fan will the delivery air temp be colder with R12 vs. R134A?

[CMONNETT]

The biggest difference between R12 and 134 is the barrier hose, oil, and the pressures used. If you're going to spend some time fixing the ac system, why use hose that is possibly 20-30 years old? You can make 134 cool just as well as R12. All you need to do is adjust the expansion valve. If you look inside the expansion valve there should be an allen bolt that is adjustable. If my memory is right, you need to turn the screw in to achieve the higher pressures required for 134. R12 needs like 30 on the low side and 225-250 on the high side. Where as 134 needs 40-50 on the low, and 275-300 on the high side. I've been in a SC with 40 degrees coming out of the vents. Something you might think abaout.

Chris
73 914 2.0
74 914 2.0
79 911SC

[svb]

Newbie question but how do I know if my AC has been converted to R134a by visual inspection? My compressor says "Nippon Denso" on it and there is a red and a blue cap on the compresssor.

[Tigerrat]

Different color cap pretty well confirms it. Should be different size as well. Supposed to have a sticker too. Ken

[white99c2]

I brought the car to a local Porsche guy here in the West Valley of Phoenix. He removed all of the 134A out of the car, pulled a vacuum then added 4 pounds of R12, total cost including labor $290.00.
The outcome; prior to the switch middle of the day here in Phoenix, over 105 degrees, kind of humid, we're into Monsoon Season here, a rotten 68 degree delivery temp out of the front vents.
After the R12 switch an hour and a half later I'm getting 60 degrees at the vents. I'm somewhat disappointed. I was hoping for temps in the 50's and I'm hearing the buzzing sound coming from the expansion valve again.
Where do I go from here, I hate sweating in the cabin and the temp is 80 degrees inside vs. 105 outside.

[JMH82SC]

4 pounds of R12? My 82SC holds 39oz. I'm vacuuming my system as I type this. I converted my empty R12 system last month to 134A and was driving down the highway with vent temp in the high 30s low 40s midday. My only problem was system lost charge in 3 days. I decided 134 was the way to go and started my A/C project. I bought a Sanden 508 compressor, had all new barrier hoses made, new expansion valve, and a new drier. While I was in this deep I pulled the condensers and evaporator to test for leaks, all checked out to be good. I cleaned the evaporator box and sealed the inside with A/C foam so air would be directed over the core and not pass the outsides and then used a non-moisture absorbing foil to insulate the entire box. Over the last 2 days I have installed the system and now have it on the vacuum pump for 5 hours. I plan to charge @ 4PM today and will post results.

[JMH82SC]

I have just finished vacuuming system for 5 hours and adding 30oz of 134A and I’m impressed. I rebuilt system on a super low budget (like add a zero to the number of oz’s in the system) and still can go out for a nice dinner with the change. Outside temp is 95 and in the garage while charging vent temp on low fan was 34 degrees. I went for a spin and this is a pic of vent temp in town with fan on high. The best thing ever is the Sanden compressor, it is QUIET compared to the York.

I can now say 100% I like 134A.

[RSTarga]

R12 and r134 use different oils and you cannot just suck out one refrigerant and add the other. They also require different expansion valves. For r134 to cool equally it needs 30% more condensor area and a more efficient evaporator+ barrier hoses. I'm running r12 and will continue to do so until I change out the complete system keeping my sanden compressor.

[white99c2]

I have confidence that the shop that did the job knows what they are doing, all they work on is Porsche. The owner told me that the compressor in my car has synthetic oil in it. He sucked out the R134A pulled a vacuum and put in 4-12 oz cans.
Today in 108 degree heat and almost 50% humidity there was 65 degree air blowing out and it was 90 degrees in the car, it was awful.
He wants me to bring the car back in first thing Tuesday Morning, I've got to get this corrected or just forget about the car until October.

[white99c2]

There still is a high pitched buzzing that resinates out of the system between the smugglers box, the air dryer and the front compressor. It sounds like a screaming mosquito, has anyone else had there A/C system do this.

[JMH82SC]

Could the noise you hear be the fuel pump? Mine fuel pump is new and has a high pitched buzz and pump is in the middle between the smugglers box and the dryer behind fuel tank.

[white99c2]

I only hear it when I use the A/C system.