need some A/C help
 

I am over on the 930 board but figured i would see if anyone over here has any input on my A/C charging issue? the link is below. thanks guys.

http://forums.pelicanparts.com/911-930-turbo-super-charging-forum/633508-freeze-12-a.html

us natives use it all the time. no problems. my 87 cab(red w/black top) is coming up for the "mutha of all a/c" systems. i wouldnt waste my time with any other freon, due to 54 yrs of baking my brains here.


heres the lowdown on what we will use:

1)new serpentine or parallel front condenser

2) new serpentine evap with whirbelwhinder fan

3) center vent

4) new serpentine or parallel rear condenser with spal fan installed.

5) brand new(we make em ourselves) dual vapor barrier a/c lines


with just freeze 12 on existing system we blow about 37degrees F on a 110 degree day.


if yer really hell bent on freezing yer teets off, i would follow kuehls train of thought and place (2) condensers in rear wheel wells. thats the best of the best and should keep ya happy. we just did a 74 ghia with dual condensers and fans in the front wheel wells and it will FREEZE YER TEETS OFF with FREEZE 12.


us ................well wez aint going that route due to weight considerations of adding (2) more condensers and fans as we track the car.


hope that native logic helps.

my issue is with the high side pressures and the car wont blow cold air above 3 K RPMS

some info from my 930 forum post

so i need a experts help. We increased the RPM to 2000 and the high side drops so we put more freeze 12 in. right now we have about 18oz in there. i know that is a lot less then whats is to be in there but the at 2000 rpm the high side was up to 275. so the weird part is when i drive it after i am at about 3000rpm the air blows warm, if i bring the rpm back down it cools down again? what are missing here? i am thinking that maybe the higher pressure may be a result of the lines that i had custom made are smaller in diameter then the stock ones. not a huge difference but noticeably smaller


............thats a good thought, its not making any noises and its pretty tight, but i will check that. one thing is strange. we charged it the first time at idle, got the temp down to like 56. drove it and as soon as i hit anything above 2K it went hot. re read some posts and some POrsche instructions and it said to charge at 2K RPM. the higher the RPM the lower the pressure on the high side. we got another maybe 4 oz in it until the high side was around 275? then drove it and we thought we had it solved until i hit 3K rpm. then just blows hot? one other thing i had to do was pull out most all of that nasty insulation that is in the smugglers box around the valve. could that be causing me a issue? or maybe the valve that is in there is stuck? Very frustrating! again though we have maybe half of the recommended freon in it! so maybe we need more? but the pressure seems to high!

That 'nasty insulation' is called prestite tape and it is supposed to be there. It's used to insulate the temperature sensing bulb and hold it against the top of the expansion valve. When you took it off what did you do with the bulb?

Agree with OJ, it should work fine. I use ES-12 and love it. Not sure about your temp/pressure/rpm issues though.

if you have a picture that might help as the gooey stuff was only on the lines, i removed a hanging piece but not all of it. there were no metal parts imbedded in it. do you have a picture of what you think i might be missing?

Remember too much freon will work against you.

My ES12a works best at 80% fill per manufacturer's recommendation.

we only have 18 0z in there? that seems to low but the high side pressure is like 275!with that presstite tape gone could that be causing a problem?

It sure sounds like it, try to evacuate, hold negative pressure for a minimum of 30 mintues then refill. Stop at 80% check temps then fill to fluid's specs.

we vacumed it this weekend and it held negative pressure no problem so i am thinking its gotta be the tape? does any one have picture of what is suppost to look like with the tape

Tape? Not sure what you are referring to. Please post a pic of yours.

its the prestite tape as mentioned above. I think mine is missing in some spots that may be causing some issues. i will try and post a pic tomorrow.

I don't have a pic of mine but I found this one in another thread:
http://forums.pelicanparts.com/uploa...1318345554.jpg

May not be the best pic but hopefully it will give you the general idea. You may want to check out this thread as well:

http://forums.pelicanparts.com/porsche-911-technical-forum/623648-ultimate-ac-thread-2011-a.html

thanks for the pic, i picked some up today, the ac guy i spoke with thinks i need more freon in there, he said the pressure is directly relative to the RPM. the higher the RPM the lower the pressure and with the lower pressure my system thinks there is no freon? makes since. we are going to put more in. before i do that i am putting this black gooey stuff on to see if that helps. I am looking for instructions on where the copper tubes are to be touching the lines but cant find any.

Oh the tar goop, OK that should not have anything to do with cooling, it just insulates that component. Refreshing will not hurt it though.

More freon? OK, I would start fresh and fill to spec. When filling the RPMs should be a steady 1800 RPMs and the lid down as you fill. Watch the high side levels it is directly related to the ambient temps right in front of the front condensor. Do you have fill guide?

Try to fill in a shaded area so your ambient temps will read correctly not off of a sun soak area.

Jim

The reason it's there is for the expansion valve to function properly. Removing it could affect the proper operation of the system. Especially if the bulb is no longer making contact. That could prevent the valve from opening to allow refrigerant to flow into the evaporator.

Well I stand corrected, mine was never tampered with or added to.

Still, try to re-fill fresh and post your results.

by the bulb i am sure you are meaning the mushroom head looking thing on top of the valve. mine appears to be soldered on. after you mentioned it being loose i checked it and its very snug. what would be the sign of a expansion valve not opening? i would think you would be getting zero cooling as nothing would be allowed to move through the system?

another great point about the ambient temp!!! on saturday when we filled it was about 85 here in phoenix and we did it in the garage and the nose was in the sun all day long. very heat soaked.