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.

Follow on to this Prestite issue. On my 88 there was tape all over the place. Is that good or bad or not an issue so long as the bulb is in contact with the expansion valve and insulated itself?

I don't think that would be an issue. Not to confuse the issue, but there's also a couple different styles - some have a loose bulb and some have the bulb attached directly to the evaporator outlet in what looks like a fitting. It's been at least 4 years since I replaced mine so my memory is a little fuzzy as to exactly which style I have. Either way, as long as its insulated with the tape it should be good.

mines connected for sure.

so we have 36 Oz of freeze 12 in. it cooled to 46 with a outside air temp of about 98 today, however it only cooled for about 5 minutes then the temp went up but the compressor was still running. we had the ball in the site glass floating after putting in the last few ounces but when we got back it was not floating any longer. then after sitting at idle for maybe a few minutes the temp came back down. it only got down into the mid 60's. the system holds another 11 oz but have read that you are to use 10% less in the system so we should maybe have 42 oz? would 6 more ounces make a difference? any one here used freeze 12 and know how much they put in. would the expansion valve be bad? bad compressor? any ideas are welcome. thanks guys. oh and the high side pressure was up to 325! so i don't think we can squeeze anything else in!

you should be using a conversion chart. xx ounces R12 = xx ounces of R134a, etc.
Also if you changed the components the original R12 capacity might not be accurate.

I usually fill based on high side and low side pressure. in fact i dont even measure the ounces. I am pulling from a 30 Lb tank so when its cold, low and high side presssures are good based on ambients.. im done.

never had an issue... sounds like maybe you have another issue? compressor staying on at higher rpm's? you have a griffiths on-off with the light that tells you if the compressor is working? evap freezing up? using a high output fan? if you shut the compressor off once it gets warm, and drive for 20 min or so and turn back on does it get cold? if so your evap is freezing. the rpm value may be conincidence...

it cools down when sitting overnight, but after maybe 20 minutes it stops blowing cold, compressor is still going as i opened the rear hatch and its still humming along. after maybe 10 or 15 minutes it will come back on.

Here is what I would do. Drive it with AC running until air gets warm, shut the AC off off and drive it another 20 minutes (sorry youll just have to sweat), turn AC back on and drive 5-10 minutes to see if it gets cold. this will rule out the evap freezing up.

did you change the expansion valve?

we did not change out the expansion valve, i wish i would have as it would rule that out and not waste 75.00 worth of freeze 12. but thats what its doing it will come back on after about 20 min.

ok its getting hot out here again in phoenix so i am trying to solve this A/C issue. it will blow cold at start up. but when i start driving and lets say the RPMs are over 3K it immediately blows hot. compressor is running front condenser fan is working. could the expansion valve be my problem? as soon as the RPM come down it blows cold again?

there is more to high side readings than amount of refrigarant,ie, air moving over condensor, with the engine lid up no air is flowing over condensor unless you have electric fans so you will get high readings. Also as been metioned here volume in ozs is just a ball park figure. You can set a fan to blow over rear condensor and bring pressures down, also misting with water will bring it way down. Sounds like your evap is icing to me, low refrigarant will cause this.

my high side pressure was higher than the book suggests. if that valve was not working would that cause this issue?

It would appear you have moisture and probably also air within your system. The water is freezing in the evaporator, plugging the system and stopping the flow of the refrigerant. I wasn't able to discern what you initially did from your posts. If the system was open to air or air introduced by the charging procedure that could be the problem. Water gets in with the air. How old is the receiver/drier - has it ever been changed?

Your system likely needs to have the refrigerant removed and reclaimed (not recycled), a new receiver/drier installed (replace any refrigerant oil there in with whatever oil the refrigerant manufacturer recommends), the system leak checked followed by an evacuation for three hours minimum with a good 2-stage vacuum pump (capable of reaching 40 microns or less of pressure) with new clean vacuum pump oil. Then properly charge per the refrigerant manufacturer's instructions.

The small OD hose likely just means that the new line was made using reduced barrier hose - it has a thinner wall than standard barrier hose but the ID where the refrigerant flows is probably the same as the old hose.

Wear eye protection and charge the system with the car fully outside, not partially in a garage.

Good luck.

so is the general consensus that the expansion valve would not cause this problem.. aim going to work on this next weekend and will order one if you guys think it might be the problem? I can get a ton of airflow over the rear condenser with some big fans i have. just getting together a list before the weekend.

Do you have a manifold gauge? An expansion valve that is not functioning well or blocked due to a frozen orifice will cause a very low than normal low side pressure and a very high high side pressure.

I'm curious about the expansion valve issue as well. What is the difference between one that works with R12 vs. R134 or the other substitutes like Envirosafe etc.?

yes we are using manifold gauges. and i will have to go back and read my old posts as i don't recall the low side being abnormal but the high was absolutely crazy. i know some of the guys wrote about airflow over the condensers and that has been verified and it seems that i have more than enough air flow. if i am idle at a stop light the cold air will start pumping away. but as soon as i start driving the cold air goes hot. compressor is still running but no cold. i would not think airflow would be the issue as when i am driving i don't see any abnormal engine temps. i am thinking its gotta be the valve? the car only has 40K miles on it and i am sure it s the original 84 valve? maybe they just go bad from no use?

bought a new dryer and expansion valve. vacuuming down now will post results when done. hopefully problem solved!

problem is solved!

What did you end up doing?

How much ES-12a (or Freeze 12) do you have in the system now?

What kind of vent temps are you getting?

Did not see an answer to Scotts question. I am doing the ES-12 on my 911 now and wondering how much gas to use?

Thx, Joe