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Old 06-20-2010, 10:41 PM   #1
5 Liter Eater
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Default A/C Not Taking a Charge - A/C Techs Step Inside

When it got hot at the beginning of the summer I noticed the AC was having a tough time keeping up so I evacuated it and tried charging it but it would not take a charge even though the clutch was engaged. What I noticed was that the low side went to ~100 PSI when I started injecting the can but the can did not get cold and the high side actually stayed at 30"Hg... So I replaced the expansion valve and tried again but same behavior. I even tried just opening the low side and pulling a vacuum and both the low and high sides went down to 30"Hg so there doesn't seem to be a blockage. So I pulled it down one more time and this time I opened the can into the high side which I know is a but I only did it for ~5 seconds. The can started getting cold so then closed it and opened the low side and it kept taking a charge. It took the ~1/2 can I had left and the high side got up to ~150 and the low side was ~40 so it was now acting normal. I put in a small can with 2 oz R134 and 2 oz PAG oil and it took that. Then the high side got up to 200 and the low ~40. I had to turn the car off to attend to something and when I started it again and tried to put some more R134 in from a fresh can it would not take any more. The high side was ~200 and the low was >120 from the pressure of the can.

So I'm assuming the compressor and/or compressor clutch is bad but I haven't seen this kind of behavior in an auto A/C system so I'm looking for any advice anyone has.

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Old 06-21-2010, 12:22 AM   #2
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I have never used one of those 'cans' before but are you sure that your connection at the low side port is opening? When you see the high pressures it sounds like you are only seeing the pressures from in the low side hose only. It's not going into the vehicles AC system. (the same when you apply a vacuum, it's only in the hose and gauges). That's my guess.
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Old 06-21-2010, 12:25 AM   #3
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It's hard to follow whats going on but it sounds like the suction valve is not being depressed by the hose. The only thing about this is if you turn off the liquid gauge valve and can pull a vacuum through the suction valve only that's probably not it.
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Old 06-21-2010, 09:46 AM   #4
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Yea there was a lot of information I was trying to convey there, sorry. I'm using a Harbor Freight AC manifold gauge set and vacuum pump to evacuate and recharge my system.

Basically I pulled a vacuum by opening both low and high side ports for ~15 min. then I closed both ports to make sure it held the vacuum. Then I attached a can of freon to the AC manifold and opened the low side but it did not suck the freon in. Whats even more odd is that while the low side gauge saw the ~100 PSI pressure from the can, the high side stayed at 30"Hg. Not until I pulled another vacuum on both sides and opened the freon to the high side did it start taking freon. Once it did that I closed the high side and let the rest of that can in through the low side and it took it. When I shut the car off and came back 15 minutes later it would not take another can on the low side. Its like the valves in the compressor are stuck.
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Old 06-21-2010, 05:42 PM   #5
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The only way to find out if there is an issue with the suction valve is to pull a vacuum through the suction side only. Attach the liquid line hose also but keep that valve closed and watch the liquid gauge to see if the system is going into vacuum.
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Old 06-28-2010, 10:08 PM   #6
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Did you ever find out what the problem was? Also check out Industrial 12a, it is supposed to run cooler and easier on the compressor than 134r and even better than R 12. It is compatable with the system "from what they say" and nothing has to be changed.
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Old 06-28-2010, 11:02 PM   #7
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Are you charging liquid or gas into the system? You should add a small amount of liquid at a time into the suction side of the system.
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Old 07-02-2010, 10:23 AM   #8
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I've been getting some tips from another forum member and found that my gauge set was faulty. It was able to let refrigerant in when there was a vacuum in the system and take a whole can but when I would try to put another can in it was not depressing the shrader valve on the service port enough to let more in. So that was hurdle #1.

After I got a new gauge set I thought I might be set but not so. Now I could start a second can and it would take it but once the high side got to ~200# the low side would start rising along with the high side. So by 250# high side the low side was 50-60, too high. So it cools "best" with one full can in it and ~30/200# but that only equates to 65-70 degrees vent temp on the passenger side and 80-90 degrees on the drivers side. Not sure why the discrepancy left to right. I've pulled the HVAC controller fuse to reset the climate control baffles and it did not help. My thought is that since the system is only partially charged that the side of the evaporator that first sees the expanding refrigerant is where the passenger side air comes from. There is not enough pressure to cool down the whole exaporator so the air flowing over the drivers side of it is not getting cooled down.

So I thought it was the compressor but the forum member said that our compressors are a variable type and pointed me at an article about a valve inside them that can go bad. http://www.aircondition.com/tech/get...9WYWx2ZXMucGRm I replaced that and the behavior didn't change.

So I'm pretty much down to replacing the compressor...
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Old 07-02-2010, 01:05 PM   #9
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one of my first cars pissed me off real good. i ended up having to disconnect the heater lines and bypass them,, not sure how it all worked, but when i did that, ice cold..
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Old 07-02-2010, 02:15 PM   #10
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Yea, I may try that first to rule out the climate control baffles.
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Old 08-23-2010, 11:28 AM   #11
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Updating this as I've done a lot but not made much progress.

Not taking a charge was due to faulty gauge set. - Fixed

When charging to spec (whether by the tables or by a SWAG of what 1.1# is) results in barely over 200# high side and driver vents are warmer than passenger vents.

When charging to ~275 high side I get the best results I've seen which is mid 60 degree vent temps when in the garage at idle with no fan blowing on the condenser. It will cool down into the high 40's but that is after extended ~60 MPH driving. Anything over ~45 MPH and it can get under 60 degrees but as soon as I slow down, or God forbid stop, it's right up to mid 60's again, most the time, high 60's. I originally had the high side as high as 300# and the high pressure switch was engaging in traffic (430#).

What I just got done doing was to remove my radiator and condenser to clean them. When I put the condenser back in I put foam weather stripping on either side so it seals the sides to the radiator. I also tapped out the bottom flange of the radiator out towards the condenser to hamper air from getting through there (rather than through the condenser). I also cleaned out the filter that is inside the bottom line to the condenser which was not clogged by any means, but not clean either. Then I filled up with Envirosafe ES-12a iondustrial. I put in two full cans and pressures were ~60/250 but I did not see vent temps lower than high 50's when driving and non-moving temps were mid 60's. I took some out as it's supposed to use less than 134a and it got a little better but not much. I'm going to play with the pressure with this ES-12a stuff but I don't think its working as well as 134a, certainly not better like they say it is. Effing snake oil...

So I've replaced the expansion valve, cleaned the condenser and radiator out, tried to improve the airflow through the condenser, cleaned out the filter in the condenser, replaced the refrigerant control valve in the compressor, almost replaced the compressor but the damn thing is compressing so I don't see how I can blame it.

Tonight I am planning to verify that the recirculation baffle is working and play with the pressures of the ES-12a.

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Last edited by 5 Liter Eater; 08-26-2010 at 01:08 AM.
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Old 08-24-2010, 06:24 PM   #12
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what are you fan settings at?
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Old 08-24-2010, 08:58 PM   #13
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0% until 180 where I command 90% from there on. And the actual percentages match.
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Old 08-24-2010, 11:20 PM   #14
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Maybe this is a stupid question, but have you tried having the system professionally evacuated and recharged with a modern, accurate A/C service machine? The one I use is extremely accurate and will report how much refrigerant was recovered from the system as well.
Higher-end models such as this one compensate for the amount in the lines, etc. I am really impressed with this one we just got: http://www.robinair.com/products/detail.php?id=2370

R134 systems are usually sensitive to charge levels. I'd make sure it had the correct amount of freon first. I've never liked using system pressure as the deciding factor when filling a system. Ambient temperature and humidity play a huge role in system operating pressures, so it can be hard to gauge where they should be.

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Old 08-24-2010, 11:23 PM   #15
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Here is a section I copied out of my "Climate Control" training manual. Has some good info on system pressures and such. Hope this helps some,

Andy



Refrigerant Pressure
Refrigerant pressure is directly proportional to its temperature so as the temperature
goes up so does the pressure and vice versa.
Refrigerant in the A/C system is provoked to change state from a liquid to a gas and back
again. During every change of state heat is either absorbed or given away in the
process. This thermodynamic property is put to use in the expansion valve to evaporator
section (Low Side) and in the compressor to condenser section (High Side) of all A/C
systems.
In the High side, dry, pressurized liquid refrigerant exits the receiver dryer and is made to
pass through a metered orifice in the expansion valve on its way to the evaporator. It is
here entering the Low side, that it quickly decompresses, expands and absorbs heat and
humidity from the passenger compartment as it changes state (evaporating) from liquid
to a gas. The low side pressure is directly proportional to the evaporator temperature
(see temp/pressure chart for R-134a) and dictates its heat exchanging capabilities. Low
side pressures should average 28 to 32 psi, that means that the actual pressure of a variable
piston displacement compressor/TEV system can be between 15 and 45 psi at any
given time.
Heat and humidity are carried away by the refrigerant gas which is then suctioned into
the compressor where it is compressed, heated and pumped through the A/C system
via the condenser. A flow of ambient air cools the condenser and the compressed, hot
refrigerant gas changes state to a liquid once again, as it flows further along the condenser.
Here the hot gas condenses into a “warm” liquid as It gives away its heat.
The high side pressure reading directly indicates the condenser cooling efficiency.
Although High side pressures may vary between 150 to 300 lb. normally they should be
about 2 to 2.5 times the ambient temperature. Depending on humidity, an outside temperature
of 80°F should produce a pressure of 160 to 200 psi on the High side
(see temperature/pressure chart for R-134a). When the High side pressure is way above
the normal it may indicate that the condenser auxiliary cooling fan is not cooling the
refrigerant sufficiently. Proper air flow across the condenser insures the efficiency of the
entire system. The cooler the refrigerant is leaving the condenser the lower its pressure;
consequently the lower the pressure of the refrigerant entering the evaporator the more
heat can be absorbed from the passenger compartment.
Note: Pressure gauges are indispensible when diagnosing A/C system BUT
they are incapable of measuring the quantity or for that matter the type
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Old 08-25-2010, 10:11 AM   #16
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RE: Charging to spec. No, I have been evacuating with a venturi vacuum to 30"Hg for ~30 minutes and then filling it to spec (1.1#) as best as I can guess with 12oz cans of 134a. 1.1# = 17.6 oz ~= 1.5 12 oz cans. The original factory fill was 1.4# or ~1.85 cans.

I gave up using the tables long ago and started evacuating and charging to weight but in this case it's not working. I don't think the spec is valid for me any more though because of the supercharger and changes to the condenser area (intercooler in front of it, no more shroud). So I started playing with the pressure and seeing how it affected the vent temperature.

It's not a bad idea to take it to a pro shop to have it filled to exact spec at this point. That suggested to me a while back but I am hard headed about taking my vehicles in for anything.
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Old 08-25-2010, 09:48 PM   #17
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Quote:
Originally Posted by 5 Liter Eater View Post
RE: Charging to spec. No, I have been evacuating with a venturi vacuum to 30"Hg for ~30 minutes and then filling it to spec (1.1#) as best as I can guess with 12oz cans of 134a. 1.1# = 17.6 oz ~= 1.5 12 oz cans. The original factory fill was 1.4# or ~1.85 cans.

I gave up using the tables long ago and started evacuating and charging to weight but in this case it's not working. I don't think the spec is valid for me any more though because of the supercharger and changes to the condenser area (intercooler in front of it, no more shroud). So I started playing with the pressure and seeing how it affected the vent temperature.

It's not a bad idea to take it to a pro shop to have it filled to exact spec at this point. That suggested to me a while back but I am hard headed about taking my vehicles in for anything.


Yeah, I hear ya. I don't let anyone touch my cars except my window tint guy, my tuner (Charlie @ RPM) and my exhaust guy if I need some good welding done. Thankfully, I'm a technician and have access to any equipment I need (and the skills hopefully ) to work on my own cars. In this case, I'd probably let someone with a modern A/C machine charge it if I didn't have access to my own.

Even with the intercooler blocking the condenser, you should not be having any problems at higher speeds if your charge level is correct. 99% of the A/C problems I encounter are related to low charge level. It can play tricks on you, too. A common sign of a low charge is one side of the dash vents blowing cool and the other side warm. Thought you said you were experiencing this.

Good luck with it,

Andy
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Old 08-26-2010, 12:51 AM   #18
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So tonight I started by playing with the pressures of the ES-12a some more. I tried adding more, slowly, and it only increased vent temps. Readings were at idle (750 RPM) with the hood open and no fan on the condenser in the garage with ambient ~89 with >50% humidity.

low/high=vent
50/225=65
60/245=67
70/275=71 (Getting crazy here but I just wanted to see)

Next I went to check out the recirculation baffle. Looking at the service manual getting at the recirculation baffle is not hard. Just take the lower passenger dash close-out off (2-3 large push pins) and the blower motor (3 small bolts) and I could see the cabin air filter that goes in the engine bay meaning the recirculation door was open. I cycled the recirculation button and no change. So I removed the baffle motor and turned the ignition back on and it moved when I hit the button. I played with it some and got it to work on the car. Basically I think it though it was closed when open so when it went to move it would encounter resistance and quit. I had previously done the baffle calibration procedure by removing the HVAC fuses but apparently it didn't work. So after moving the motor one way and re-installing it, it works again. I switched back and forth several times and it moves as it should. The air blows harder now with the recirc on now just like it should and the temps are colder. It gets down into the low 50's and even high 40's when driving for just a short time even at slow speeds. If I sit and idle long enough the temps come back up but it takes alot longer now for them to rise and as soon as I start to move the temps start to drop again quick. I decided to play with the pressures again.

With recirc on (and actually working), idling in the garage again:

low/high=vent
55/225=63
43/190=60
41/175=59
35/165=58

BTW, the table for the temp and humidity says 22-33/174-202=57 so it's actually pretty close. I was surprised.

As soon as I close the hood the 58 temp went to 60. I saw this increase when the recirc door was busted except even more drastic, temps went from ~65 to ~70. :O I think I now have an excuse to purchase a heat extractor hood. Driving around, even slowly, it gets down to 53 and stays there; very stable. At a stop temps slowly come back up to ~58 (takes like 3 minutes) but as soon as I move they quickly go back down to 53. I got lower driving temps with the pressure a little higher, like 50/225, but the idling temp was also a little higher. I may add a little more a bit at a time (5 low side) and drive it each time to see what the best mix is of idle and driving temps.

I went through four cans of the envirosafe ES-12a stuff playing with pressures up and down. I have two more but I may switch back to regular R134a to see if it's better or worse or the same. I had already been through half a dozen cans of R134a before trying the envirosafe.

I haven't done a DTC scan with my HP Tuners in a while but I'm not sure it would show me a body module code if it were even throwing one because of the recirc motor. I think I've been driving it like that since I got it! That explains why I was getting an oil smell in the cabin when I had my PCV delete and vented to the atmosphere. I couldnt understand why I smelled like oil after a drive even when the recirc was on...

So, after ~10 cans of refrigerant, replacing an expansion valve and a refrigerant control valve that I didn't need, purchasing and returning a compressor, and ~20-25 hours of labor, I think it's finally resolved...
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Last edited by 5 Liter Eater; 08-26-2010 at 01:17 AM.
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Old 08-26-2010, 01:33 AM   #19
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Had kinda a tuff time following your issues but If you pull a vacuum and then it wont pull out of the can into the system at least 6oz's or so then the gauges or fittings are at fault.

The best way to tell the AC performance is to have air movement (fans on high are usually enuf) and the RPM's around 2-3k. At idle readings are kinda misleading at times because the car is low rpms and the interior temps are hi and havent been recirculated which raises low side pressure and of course isnt circulating antifreeze or freon fast enuf to cool stuff down..

You can only expect to drop temps of around 20 degrees (interior temp versus "vent" temp (stick a thermometer int othe vent and then set it in the front seat) until all the air is circulated. So if your car is 80 the the vent temp 60 its doing ok. Expect the vent temp to be around 45-48 with outside temps around 90 with the rpms at 2500 after five minutes of running (usually the air is all circulated at that point)

A blend air door sticking or the recirculation door not opening will give you great ac pressure readings but terrible inside temps. Dont know if that helps but hang in there, the journey to the repair is always more depressing then the fix

Last edited by HANNY; 08-26-2010 at 01:36 AM.
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Old 08-27-2010, 10:40 AM   #20
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Drive home yesterday was a good test. Nice and hot outside and traffic as usual. Vent temps were very consistent from 53-55 degrees. I'm pretty happy, although my beater 2000 Honda Civic blows low 40's.
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Old 08-27-2010, 10:40 AM
 
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