R 134 AC Charge problem...about to give up!
 

OK...same story as last summer...can't seem to get AC to work/recharge. Here are the basics:
New: Hoses, TXV and evaporator, compressor (Sanden) and add'l condenser with fan.
Vacuum down system (new Mastercool Vac pump as well) and now have made a hose system that allows me to vacuum out hoses so don't have to "bleed" system.
-Put 12 oz can in warm water, engine off, allow can pressure to empty into system, low side only open. Pressures on hi/low about 100. Shut valves and vacuum out hoses, add 2nd can and allow it to empty then start car and turn ac on full. Here are the pressures (90 degrees/Dallas/humid)
10-20 seconds see 50/150
30 seconds 40/200
1:30 32/210
4 mins 37/240 about now 2nd can is empty
Vacuum hoses and add 3rd can
VENT temps still around mid 60's which is where they went to and stay the whole time
adding 3rd can now, pressures are
6:30 mins 40/265
10 mins 45/235 Vent Temps STILL in 60s
14 mins 47/350
The general consensus is I've allowed air into system but I don't see how, in particular now that I can isolate the hoses when changing cans.
Is it possible there's something wrong with the new TXV/Evaporator?
In the spring on milder days it would get into mid 50s. I've inserted a temp sensor into the coil and seeing upper 50s so that's in line with the vent temps.
One thing I noticed is the vacuum gauge never quite goes all the way to 30. It holds vacuum but never makes it to 30, only goes to 27.5/28 an stays there. Seems to hold vacuum, next step is take to AC shop and see if I'm doing something wrong.
Thanks for any tips.

Vaccum.
 

How long does it stay @ the 27-28 level?

Show us your "vacuum out" connections.

I suspect a crimped A/C line O-Ring.

I replaced the entire A/C on our '86 last year.

Hang on to your wallet & pm me as needed.

Gerry

It will hold at that level for a long time. Also I took off all the hoses and put brass threaded sealed caps on the gauge connections (so only a single hose going to pump) and it still only went to 27.5 and would hold there for 2-3 hours, dead solid. The high side shows well past zero. I am thinking it may be the gauge is not quite calibrated correctly? There is an adjustment I believe.

I just did the AC in my 84 with good success. I'm just up in Grapevine, TX. If you'd like to bring your car by I would be happy to give you a hand to see if we can get it sorted. I'll PM you my number.
What RPMs are you at with the pressures you mention? 350 seems like your high side is getting pretty hot. Are you running is with the engine lid open or closed? If open you have lost all air flow through your engine lid condenser, which will severely decrease the efficiency of the system.

Vacuum values.
 

I'm betting on a bad/pinched O-ring/loose hose/ connector ect.....

Use the dye and/or a sniffer & look for a pressure leak(s).

Kuehl will probably chime in after the holiday......

Gerry

Do you have any fans running on the condensers? External?

Something fundamental is wrong. At 37/240 the output should be nipply.

My SC AC with a dead front condenser fan can spit out 55F in moderate humid 80F.

Buck... you did not mention new R/D---will assume that is new too. Will also assume:

1. you worked vacuum of charge line when swapping cans so indeed no air is in system
2. rear lid was closed and sealed so engine's fan is moving air over rear lid condenser
3. engine's surrounding tin--all parts--is installed
4. engine's seal is in place and making good contact all around
5. all existing condenser fans are working when AC is ON
6. condensers are free from obstructions

Like so many of us with our 911 ACs... I was fed up with it too. The only answer for me was to take the whole thing apart and begin a quest to sort out the holy grail for system-pressure-temperature optimization. (Am not there yet but closing in on it.)

Below are four test results for a 3 condenser system. Each result is based on the given weight of 134 introduced to the system and the resulting hi/low pressures for each weight. All this data is for R134a with the engine at idle and the rear lid closed, lid tape sealed all around, all engine tin in place, a good engine seal, and the rear lid condenser having a foam seal all around between it and the rear lid (point being to optimize the suction of the fan and maximize the air flowing through the condenser), clean equipment, and both condenser fans operating. Evap is a Kuehl serpentine and the 3rd condenser is a Kuel with fan. Bottom line: MORE refrigerant/pressure did NOT decrease v-temps. Less did!

http://forums.pelicanparts.com/uploa...1499119936.jpg

33 dF at the vent was achieved in city driving (in Miami) with a 26 dry hose* weighted oz charge. (Having hit 33 dF I did not test any lower weighted charges---it's possible less refrigerant performs even better.)

http://forums.pelicanparts.com/uploa...1499119936.jpg

What I'm getting at is there being potentially too much refrigerant in your system. A high pressure of 350 (am assuming this is at engine idle) suggests this.

I'm not saying this is THE answer... rather, it's a possibility to take into consid. Other opinions are called for.

Excellent you recorded time increments. Based on all your numbers, I think at around 3:15 minutes the system was charged. A consideration in regard to timing is it takes a bit of time for the system to assimilate refrigerant and respond at the vent. Specifically how much time... I don't know. Is a good question. At your 4 minutes... pressure is already above proported optimal and 2 cans are in (minus what sits in the hose)... and the third can is on its way in. Am voting for a major pause after 20 weighted ozs to allow system to "assimilate." Check pressures and v-temps after major pause. Then, moving ahead in very small increments with major pause between each addition of refrig.

EDIT: How long did you evacuate system for?

The final question which perhaps should be the first... is your thermometer good? Confirmed with a 2nd thermometer?

* "Dry hose" means there is ZERO refrigerant in the hose system when the scale is set to zero (tare'd.) In the end this means that there's actually slightly less refrigerant in system than 26 ozs because some refrigerant remains in the hose when the tank is closed and the final weight of the charge is taken.

I just put my AC back together, and i kind of had the same issue. I have an SC turbo conversion with a huge full bay intercooler. I have 2 993 condensers, 1 mounted in the rear wheel well, and 1 in the front wheel well, both with cooling fans. I also have a Keuhl front condenser. I was having problems not getting cool air out of my vents(about 60 degrees) Turns out, the expansion valve tubing that was supposed to attach to the line coming out of the condenser, the clip had slipped off, and was no longer making a good connection. As soon as i got that secured again, it started blowing in the low 40s on high speed with 85 degree temps with pretty high humidity. It still isn't exactly where i want to be, but as good as it gets with a stock evaporator core. On low speed, and lowest temp setting on the switch, the compressor will cycle.

how cold does the suction line feel off the evaporator, and at the compressor??
the pressures are a bit on the high side after the last can, like air flow over the condensor is minimal..

I have just ran into a problem on a 85 like this, most of the air was forced around the evaporator instead of through it, the low side or suction lines were ice cold.. 48* at the compressor

350 is high but not quite at a plugged something or other.

I can imagine front condenser fan not working. Just saying, not accusing.

Hot ass day in Dallas, no extry flow from a big fan up front.

Addl condenser added. Once the factory balance is messed with, sometimes less is more.

12 oz cans? Nut up and buy a 30lb tank. R134 is getting sort of spendy, though.

You pulled a vacuum that is decent. It held. You don't have leaks.

Tell us about you new receiver dryer...................... This is required and you don't mention it, unless I missed it.

Ok thanks for comments and help, forgot to mention new R/D, did have big fan on the deck blowing into condenser with lid nearly shut. The front condnesor fan is working and added fuse many years ato. Thermometer has been confirmed with 3 other digital temp sensors on my Voltmeter, system has been evaporated for hours at a time or for couple hours others, did not seem to change results. Disc seven you may be onto something. I was assuming I needed to get to around 40 oz or 85% of full charge with R12. I may drain some to see if it changes. Thanks!

Cool. Just doing the basic sense check.

Buck, with the current temps here, you want to shoot for lowside pressure of 28-30 and highside pressure of 220-230 at engine idle speed (approx 900-1K RPM) . . . charge amount above that will result in much worse performance (aka - higher vent temps).

Not sure if refrigerant volume is going to be your "only" problem, but is definitely a starting point.

PS - KinkyKarl sux, and Bobasaurous, too (Targas, after all)!!!! :D

Assuming your gauges are accurate:

At 90 F ambient, 24 oz 37/240 OR 36 oz 47/350 suggests air in the system or insufficient condenser capacity. The system should never be charged with fans blowing on condensers that will not be blowing on the condensers when you are driving the car; that is not reality. Condenser fans that are permanently part of the system (front condenser blower and fender condenser blower) should be operating when the thermostat makes contact (compressor clutch engages), and evaporator speed of say 2 for stock fan speed control blower systems.

All charging procedures and pressure tests should be performed with front hood down, windows up, fresh air controls closed, doors closed, deck lid condenser resting down on it stops (be careful of your service set hoses), thermostat set at max cold which is fully clockwise (CW).

12 oz with static pressures of 100 are way too high. If this was true observation this also suggests ambient gases (air) in the system.

If your evaporator core temperature is 50F you can't expect a vent temperature lower than 50F. Things that can create a 50F evaporator core temp at 90F ambient are insufficient qty of refrigerant (that is not your issue), air mixed with refrigerant, that is a possibility, a TEV that is stuck open or partially stuck open (say from moisture frozen in the TEV or debris; a closed TEV would reflect lower low side pressures which you do not have), a frozen evaporator core (you are anywhere near that yet), debris on the evaporator fins which prevents heat transfer (not your case with a new evaporator core).

In a normally functioning system you will see frost or moisture at the evaporator outlet and possibly back a the compressor inlet depending upon how good the system is. The refrigerant lines all along the course from the first condenser outlet, past the last condenser outlet, to the drier, out the drier and up to the TEV inlet will be hot to warm (temp drops are move closer to the TEV). If you find a cold spot anywhere before the TEV on this high side circuit that would suggest a significant reduction in the aperture of the lines ID which is creating a change in state of the liquid refrigerant back to a gas which results in a change of temperature (alike what your TEV is suppose to do).

New TEV's and old OEM TEV's seldom fail on their own, debris or moisture tend to be the issues. New evaporator's as well tend not to malfunction out of the box.

Having a procedure or set up to eliminate the possibility of air entering the system while charging is a good idea. This is a very common issue to run into. Here is where a 4 line service set (high, low, vacuum, refrigerant) and a 30 lb can come in very handy. Explore that something seems a bit our of character in your static pressure (100 psi with 12 oz) and your high side pressures as you continued to add cans; what you noted in pressures moving from 12 oz to 36 oz is alike adding too much refrigerant to a too small system (air in the system has that affect). The high is simply too high compared to the ambient. What you may wish to do is delete the system you have added to your service set. A standard can-tap valve system on the end of your vacuum/charge line (if you are using a 3 line set), should allow you purge the air in the line with refrigerant before you add your first can, and it should allow you shut off that line at the valve where the can is tapped reducing the amount of air that could enter.

76FJ55 offered to lend you hand. In times like this a 2nd set of eyes can be very helpful. Throw a few beers in your Igloo and drive over.

Happy 4th of July to all.

Bobasaurous and Kinkyme... we drive our Targus in the hard & fast lane Rono. Your smurbo coupeee just sits there... ya wind up the rubber band engine... and all it does is make snow cones---albeit good ones. :D

HAPPY REVOLUTION DAY!

For a reference point, my car has 2 993 condensers, no factory condensers. Factory evaporator. Kuehl Wirbelsturm fan wired directly to the battery (so it's even STRONGER)

I run 23-24 ounces of R134 in my car. Now, the hoses are slightly shorter than factory, and I don't know how the capacity of 2 "modern" 993 serpentine condensers is compared to the old factory tube condensers.

30 degree delta at the vent within 5 minutes of driving at Super High fan speed.

so at 85 degrees, you are pumping out 55 degree temps at the vents?

88911coupe, spray some water on the front condensor with the rpm at 1200-1400.
when you spray the condensor with water the pressures will drop substantially.

feel how cold the suction line is off the evaperator,

Let me know if you want some hands on help. I just redid my system rebuilding all my lines with barrier hose, installing a serpentine evaporator and adding a rear fender condenser (adapted from an Isuzu box truck) with a 10" spal controlled by a trinary switch.

r134. 90 degrees=105psi. as long at this was not a can that was in hot water.
let the system sit over night and check resting pressures again.

2 cans was not far from what you needed in there. also depends on engine RPM. check pressures at around 1500rpm, windows closed, fan on hi and recirculate.
hi was a bit hi but I don't think so for these cars. condenser area is still small and air flow is poor.
notice your low side went up on the 3rd can. but still depends on RPM.

you don't need a fancy system to purge the lines.
after connecting the new can, burp the line at the gauges.
if you feel the need to go the extra step, connect the new can, don't puncture it yet. open the low side gauge then burp the line to the can. close the low side. puncture can then burp the line at the gauge. then fill.


how much oil did you put in the system?
kuel will know better than me if too much will cause this problem of low vent temps.

you may try driving it a few days and see what it does.

I know kuel does not like this but I leave the deck lid open and put a box fan on the rear deck lid on low. pressures will go down when driving due to better air flow and higher engine RPM.

24 oz will be undercharged ("and add'l condenser with fan."); I'd guess by 33%

Based on the system pressures with 12 oz report in the original post, and running pressures (as stated before)... system has signs of atmosphere (air in the system).

Ok...thinking of getting a micron vacuum gauge...that would tell me if I've still got ambient air in the system....correct? Looking at the Robinair RAVG-1.

so at this point you may look for a shop to charge and check the system.
I charge $70 plus freon, dye and oil, and you will get my 33 years of experience in automotive ac.
and if it goes flat I will check it over with the UV light as part of my ac service.

A micron gauge is more accurate than a typical analog low side gauge. It can help you with testing your pump, your manifold and service set, verifying system leakage rates, and determining system's vacuum level more precisely. However, it won't tell you if you have air in the system, it only conveys the level of vacuum in a different scale.

There are a many brands of micron gauges out there, from simple inexpensive units expressing the level with led's to units with lcd displays. In selecting a brand you just have to take in all the factors: price, warranty, tech support, number of times per year you will use it, ease of use, etc. I have 3 hanging around the shop, each is like a character in a novel.

UV dye will not expose leaks that lack refrigerant oil weeping from the source. Visual tools, such as UV dye tracers or soap and bubbles are limited to working in areas where you can see. Electronic leak detectors, such as a common heated diode type, are the preferred tool for pin pointing leaks; but they are limited to their ppm sensitivity, meaning ....you won't detect low permeation rates in old non barrier hoses.

88911coupe, still has the problem of getting the car, vac and charged correctly
so dye and sniffers do not come into play yet

If he is following good procedures and can't pull down a good vacuum, and his pump is doing a good job, he will need to find the source of the leak, hence a shot of R134a in the system, gauge and manifold set, and then use an electronic leak detector.
Just went through this with a brand new electronic manifold. The micron sensor was defective; leaking.

if he was close
I would hook him up

Hoping the micron gauge will help me confirm my vacuum's pulling a vacuum...I'm 99% sure it is but this way I'll be able to confirm. As Griff has pointed out, it looks like I've got ambient air in the system so at least this way I'll be able to determine if its something I'm doing wrong in the re charge.

I agree a micron gauge will not tell you that you have ambient air in the system. But is can be used to ensure the system is tight and that moisture has been evacuated from the system.

JB Industries has a good technical paper on Deep Vacuum, Its Principles and Application.

I used a BluVac Digital Vacuum Gauge for evacuation of my system.

BluVac Manual

Offer is still open to assist in sorting this out. I know last time I offered, you were thinking of taking it to an AC shop, but looks like you're still fighting this on your own. I don't have a leak detector, but I've got a working Vac pump, gauges, and also a Dry nitrogen tank we can use to pressure test the system for leaks.

OK...got the gauge and tested it today...going to be 100 here in Dallas. I just used a single hose hooked up to the gauge to remove as many variables for leaks. This was with oil left over from last vacuum pull, not fresh. Immediately dropped to about 4,000 and stayed, no further, then i snugged up the gauge threaded into the T fitting and each small turn (10 degrees maybe) it would drop again. Once it got to about 1850 microns it stayed there. Thats no where good enough is it? Next test it to put fresh vacuum pump oil in and see if it will go lower.

Buck, my personal opinion is that you are not doing the procedures correctly. There are some real good threads here that are easy to follow carefully. This is not really that difficult if you do each step carefully and thoughtfully. This is a good one.

http://forums.pelicanparts.com/porsche-911-technical-forum/834136-my-ac-burns-me-up-summary-fix.html

Show us some pics of your equipment and your hookups for a start to help us get you thru this.

Just to clarify the test I just did was not hooked up to the ac system, it was just the hose hooked up to the pump and micron gauge. Basically just wanted to see what the vacuum pump can do.

A good pump should be able to pull down to about 40 microns (29.915"). Was the charging manifold (gauges) attached to the vacuum micron gauge?

Could be improper oil level in the pump. Too high or low some pumps are fussy about that.

When was the last time you changed the oil on the pump?
Change the oil after each use.

The "ideal" vacuum of 500 microns on the system is a good indicator that the system does not have any leaks. On a 911 ac system with what seems like miles of hose will be difficult to get that low. Refrigeration oil in the system and the hoses out gassing plus residual refrigerant you would probably be lucky to hit 700-800 microns on a new clean system. YMMV

Interesting tidbit of info (maybe!) that at 500 microns, the pressure in inches of mercury is 29.90. Pretty close to a pure vacuum!

Your measurement of 1850 Microns at the pump would be about 29.85" hg gauge.
29.90 and 29.85" would be pretty difficult to see with the compound low side gauge.

I am not a huge fan of leak testing a system using a vacuum. Leaks allow air and moisture into the system and some types of refrigeration oil is highly hygroscopic and will absorb the moisture from the air.

Try to isolate your equipment problem to pump, hoses or manifold and see if you can get that pump to perform.

Update to the update...I added teflon tape to the threads on the gauge and now am getting down to around 380 microns. This is not new oil, just wanting to see how it worked just hooked up to the pump. Next I'll put new oil in and see what I can achieve in a real test.

ideal is 500 microns.
I have done this on my brothers 930. I never got 500 and each time he said just charge it. I did and it all leaked out.
no need to change oil. 380 is good.

I agree,. leak testing with vacuum os not good but we all do it/have done it as needed. nitrogen is best. charge it and see if it holds. also charge it then vacuum and repeat is best way to remove moisture. I have heard nitrogen is not good for 134 systems(?). I still used it on my 930. found a leak at the condenser but still have not fixed it.

if you cant reach 500, leave everything connected, turn off the pump and see if the micron gauge holds. if you get it down to say 1000 microns and it will hold it for a few days with the pump off I would charge it.

these are very large systems with a lot of places for leaks.

Found this...year later and same problem. Last week pulled vacuum and saw no leaks overnight, then did recharge using a hose set up that allowed to to vacuum out recharge hose between cans. Still same problem, getting 40 Psi on low side and low 300's on high side after just 2 12 oz. cans and vent temps only about 60 degrees. Decided to take it to old, respected AC shop here in Dallas (McCains) to see if I'm doing something wrong. I did not evacuate/vacuum it before I took it to them. The pulled out the r134 and vacuumed it down then put about 44 oz of R134 and got same results as me....42 psi on low side and vent temps about 60 degrees. The foreman did say he thought air had been in system but said they "purge" it before recharging to make sure no air in system. I told him there are guys with set ups similar to mine getting vent temps in the 30s so he's as confused as me. Not sure what to do now other than just accept the poor performing system. With all the enhancements I've done I was expecting better results.

Best way to test your service manifold and service hose set is to pull a vacuum on an empty 30 lb refrigerant can. Ideally you want a 4 valve 4 hose service manifold: low side, vacuum, refrigerant and high side. Pull down to say 200 microns if you can. Close your vacuum valve. Don't be surprised to see the micron level rise to 500 microns within a minute or so, then it should level out.

"40 Psi on low side and low 300's on high side after just 2 12 oz. cans and vent temps only about 60 degrees."
At what ambient air temperature around the car?
Was the rear deck lid down resting on the service hoses?
Is the front condenser blower motor running?

"They pulled out the r134 and vacuumed it down then put about 44 oz of R134 and got same results as me....42 psi on low side and vent temps about 60 degrees."
42 psi on low suggests an evaporator temperature of 47 degrees. A delta of 13 F degrees between the vent and evap core .
Stick a digital thermometer in the evap core to observe what its temperature is.
In general terms, with a normal operating system your evaporator outlet hose fitting will be sweating or frosted on a good system.
If your evaporator core is near freezing and you are seeing much higher vent temps then inspect for air leaks between the plastic evaporator outlet tube and the center vent.

Buck, according to a Sanden troubleshooting chart that I find useful, when both high and low sides are high, it typically means insufficient condenser airflow and/or an expansion valve that is not working properly (or its intake screen is somewhat plugged - it it has one of those).

Of course, you don't really need a chart when you've got Griff posting here, but it does come in handy, and breaks down the basics of how mobile a/c systems work.

https://www.sanden.com/objects/SANDEN_SYSTEM_DIAGNOSIS_CHART.pdf