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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.
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Buck
'88 Coupe, '87 Cab,
'88 535i sold '07 A4 sold, '14 C250 DD
Warren Hall, gone but not forgotten
Old 07-03-2017, 10:19 AM
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Vaccum.

Quote:
Originally Posted by 88911coupe View Post
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.
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
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Last edited by 86 911 Targa; 07-03-2017 at 10:54 AM..
Old 07-03-2017, 10:52 AM
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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.
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Old 07-03-2017, 11:11 AM
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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.
Old 07-03-2017, 11:17 AM
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Vacuum values.

Quote:
Originally Posted by 88911coupe View Post
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'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
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1986 911 Targa.
Per Road and Track magazine:
Only in L.A.:
In the window of a bar in Hermosa Beach, California.
"Happy Hour prices during all car chases."

Last edited by 86 911 Targa; 07-03-2017 at 04:37 PM..
Old 07-03-2017, 02:00 PM
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Do you have any fans running on the condensers? External?
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Old 07-03-2017, 02:43 PM
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Quote:
Originally Posted by 86 911 Targa View Post
I suspect a crimped A/C line O-Ring.
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.
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Old 07-03-2017, 02:59 PM
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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!



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.)



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.
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Last edited by Discseven; 07-03-2017 at 03:53 PM.. Reason: How long was evacuation?
Old 07-03-2017, 03:46 PM
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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.
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Last edited by scottrx7tt; 07-03-2017 at 04:11 PM..
Old 07-03-2017, 04:05 PM
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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
Old 07-03-2017, 04:16 PM
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Quote:
Originally Posted by Mike R. View Post
the pressures are a bit on the high side after the last can, like air flow over the condensor is minimal.
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.
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Old 07-03-2017, 06:58 PM
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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!
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'88 Coupe, '87 Cab,
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Old 07-03-2017, 08:08 PM
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Quote:
Originally Posted by 88911coupe View Post
The front condnesor fan is working and added fuse many years ato.
Cool. Just doing the basic sense check.
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Old 07-03-2017, 08:14 PM
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Quote:
Originally Posted by 88911coupe View Post
. . . 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!
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)!!!!

Last edited by Rawknees'Turbo; 07-03-2017 at 08:30 PM..
Old 07-03-2017, 08:27 PM
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Quote:
Originally Posted by 88911coupe View Post
add 2nd can and allow it to empty then start car and turn ac on full. Here are the pressures (90 degrees/Dallas/humid) ...4 mins 37/240 about now 2nd can is empty, VENT temps still around mid 60's which is where they went to and stay the whole time ....
adding 3rd can now, pressures are,
Vent Temps STILL in 60s, 14 mins 47/350
.
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.
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Old 07-04-2017, 05:31 AM
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Quote:
Originally Posted by Rawknees'Turbo View Post
PS - KinkyKarl sux, and Bobasaurous, too (Targas, after 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.

HAPPY REVOLUTION DAY!
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Old 07-04-2017, 05:38 AM
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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.
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Old 07-04-2017, 06:06 AM
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Quote:
Originally Posted by Pazuzu View Post
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?
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Old 07-04-2017, 06:40 AM
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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,
Old 07-04-2017, 06:52 AM
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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.

Last edited by 76FJ55; 07-04-2017 at 08:41 AM..
Old 07-04-2017, 08:28 AM
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