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a/c not cooling Pages: 12

mak11 on Tue August 19, 2008 10:16 AM User is offline

Year: 2004
Make: chevy
Model: cavalier
Engine Size: 4cyl
Refrigerant Type: r134
Ambient Temp: 70
Country of Origin: United States

What pressures should the low and high side be on this cavakier?

TRB on Tue August 19, 2008 1:18 PM User is offlineView users profile

Compressor Type
2.2L Delphi CVC-6
Total System Oil Capacity 6 5 ozs.
Refrigerant (R-134a) Capacity 2.2L 1.5 lbs.
System Operating Pressures
High Side 164-231 psi (11.53-16.24 kg/cm2 )
Low Side 26-38 psi (1.83-2.67 kg/cm2 )

With ambient temperature at 76-85°F (25-29°C) and humidity above 60 percent.


When considering your next auto A/C purchase, please consider the site that supports you:

mak11 on Tue August 19, 2008 2:55 PM User is offline

I have this 2004 Cavalier that reads the right pressures as you posted above. But it does not cool any. not even a little bit,
I was told that it may be a clogged expansion valve and had it changed but still nothing.
The car has only 60K miles.

mak11 on Tue August 19, 2008 3:00 PM User is offline

I accidently hit the enter button an posted before I was done,
I wanted to ask what else might cause this?

GM Tech on Tue August 19, 2008 3:16 PM User is offline

That is what the "edit" button is for....

Check your temp door cable-- does it stroke and slam shut full hot to full cold?

The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

mk378 on Tue August 19, 2008 3:29 PM User is offline

If the line from the evaporator back to the compressor is getting good and cold, it is not a refrigerant problem. It should be cold inside the car too unless the heater is fighting the A/C.

mak11 on Tue August 19, 2008 4:12 PM User is offline

The high and low pressures are correct but no lines get cold.
The High line gets hot but the low line stays only lukewarm.
Thats why the expansion valve was changed.
If the heater was fighting the ac, wouldn't I at least have a cold line behind the expansion valve?

mak11 on Tue August 19, 2008 5:25 PM User is offline

I checked it out again and the line is lukewarm (or maybe a touch of coolness) behind the expansion valve but completely lukewarm where it goes into the evaporator inside the car.
With the pressures right this seems impossible.
Any other ideas?

mak11 on Tue August 19, 2008 5:57 PM User is offline

There is only one reason that I can think of that this is happening.
My condenser is somehow plugged up so that only low pressure is going through the orfice in the expansion valve.
Did anyone ever hear of a condenser plugging up to that extent, especially in a 60K mile, 2004 model car?

kylea on Tue August 19, 2008 7:06 PM User is offline

If you think your condenser is plugged (which I doubt it is) you can test for it by checking the inlet and outlet temperatures on the lines. The condenser's job is to take hot liquid freon and then dissapate heat from it. You should have about a 30 degree temperature drop from the inlet of the condenser to the outlet of the condenser. You will want to use a good thermal coupler or infared gun (mind you cheap infared guns are not that accurate) to check for this.

Does the AC work at all before the motor gets too warm? Of course you would want to check the blendoor... to do this you should pinch off the heater line with maybe a large C clamp and two pieces of wood. Once you have pinched off the line (well enough so that no antifreeze can circulate through the heater core) let the vehicle run for a little bit and see if you get any cooling.

All this information is assuming you have a correct charge of oil/freon. This system calls for 5 ounces (total) of Pag 150 and calls for 24oz of R134a

Also, this vehicle has an orifice tube, not an expansion valve. I would be curious to see exactly what your evaporator outlet temperature is.

NickD on Tue August 19, 2008 8:25 PM User is offline

My manual shows three variations of the V-5 compressor family, probably one is made in China, another in China, and the third in China, this compressor runs all the time if the AC is switched on and the ambient is above 38*F. You say an expansion valve, actually it's an expansion tube or more basically just a fixed orifice. Why did you have that changed and what is the repair history of your vehicle, that would shed some light. Is the compressor always running? Stuff like this is obvious with the vehicle under our noses, but only have your words to go by.

Circuit itself in terms of external components is next to nil, the climate control feeds a variable voltage to the BCM from the mode switch, that controls the vents, bend door is cable controlled as GMTech said. Blower is conventional resistor with a high speed relay. A dual function sensor feeds the PCM that in turn fires the AC relay, that is about it. V-5's are known for control valve failure, but your pressures would be affected. Who did the work on your vehicle and was it properly charged with a deep vacuum? When someone reports near normal pressures and a warm evaporator outlet tube, air in the system comes to mind.

When my temperature gauge starts edging above 195*F, that tells me it's time to clean the condenser/radiator fins. With these systems, best to charge by weight, was it charged by weight?

I have more questions than you have, LOL.

mak11 on Tue August 19, 2008 11:46 PM User is offline

I believe the air conditioner has never been worked on before.
Only I put a new orfice tube in it which I thought may be plugged, but it acts same as before, Line not cold just after the orfice tube.
The compresser puts out high pressure, BEFORE the condenser but seems the high pressure doesn't go into the orfice at the outlet of the condenser.
Actually its a DIY job as I have done many many in the past being a insurance care rebuilder but never had a condenser plug up before which I think it has to be.
Although I never yet had a plugged condenser, and don't know if if anyone has, but I'll just try replacing the condenser.
Thanks for the reply.

iceman2555 on Wed August 20, 2008 2:43 AM User is offlineView users profile

A luke warm suction line....pressures that are 'correct' (?) was the system charged...with the correct equipment to insure a complete charge...or with cans and charging to pressures? Have a very sneaky was the latter...and if so...the system could simply be undercharged. Try this test...max cool..high blower...engine idle...doors open...the electric fans must be energized...check the inlet/outlet temps of the evap...should be the exact same..or within 3-5 degrees of each other...when this occurs....the system is matter what the pressures are...the system must be totally charged...first and foremost.....if a high side pressure problem occurs after this....then repair the cooling not remove refrigerant.

A variable will maintain a certain pressure range...even when undercharged.....get the system charged properly.

Another aspect...check the temp drop across the orifice....if the orifice is not seated properly....high pressure liquid will by pass the orifice and result in a loss of cooling, however. If the liquid line is hot prior to the should be cold immediately after the orifice....if could be a by pass of liquid refrigerant.....reference the low pressure indicated.
Think the system is undercharged.

A restricted condenser....???? highly doubtful....and if the condenser is restricted...what produced the debris ??? first thought would be the compressor...this is not an uncommon problem with a system that has been operated with an undercharged system....lack of lubricant flow due to inadequate refrigerant. So, if the condenser is restricted....seems the compressor is headed south also.

kylea....go back an re read the part of Basic Auto A/C that describes how a condenser functions.....from your description...."The condenser's job is to take hot liquid freon and then dissipate heat from it." The refrigerant entering the condenser is a high pressure/high temperature liquid.....does that mean that the compressor actually produces and pumps liquid refrigerant????? Check it out.....

The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

iceman2555 on Wed August 20, 2008 2:56 AM User is offlineView users profile

One other aspect comes to mind...esp if the system is properly and completely recharged...have encountered this a few times....vehicle comes in for a basic cooling....system recovered...recharged.....pressures are within margins.....but no cooling....nada....
What we discovered.....replace the compressor.....and other associated parts.....disassembly of the compressor indicated severe internal damage due to lack of lube...the condenser was somewhat restricted....we cut it open also.....we theorize that the engine cooling temperature is sufficient to produce pressures....high side forces refrigerant flow thru the system....a temp/pressure drop across the orifice...simply not enough to produce cooling. To produce 200-245 psi high side is not necessary for a tremendous amount of heat to be generated into the condenser to produce this phenomena. Can not prove why this occurs...or why it occurs in one model and not another...but in several different vehicles we have experienced this condition.
Just a few words of thought.

The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

NickD on Wed August 20, 2008 8:01 AM User is offline

Based on a recent EPA report, R-134a passenger vehicles can lose on the average of 10% per year without what one may be considered to be a leak. This was not a command for the OE's to do better, more like a please. So with a four year old vehicle, possible to lose 40% of your refrigerant. With a system capacity of only 24 ounces and a 10% loss, that is only 2.4 ounces per year, those kind of leaks are not easy to find.

I feel you erred by opening your system, moisture can seep in and turn your PAG to sludge and would never do that without a flush and replacing the accumulator, hey, that is the way they are made. A more logical step would have been to recover, add the correct amount if needed, that would also tell you how much refrigerant you lost over the four year period. And if done correctly, moisture would have not entered the system. Would have also checked the entire system for any visible signs of oil seepage, just by habit with GM vehicles, like to pop off the clutch hub so my eyes can see the seal and also remove the blower motor and see what the evaporator looks like. Always find debris that needs to be cleaned up and cleaning the fins is always the first step in servicing an AC system. You just have one tiny condenser fan in this vehicle. Also prefer using a good electronic leak detector particularly around the service port where refrigerant can leak out without signs of oil seepage.

So should we go ahead with the theory of a plugged orifice or a condenser? Did you ever know if your charge was correct? Based on average losses, your system could have well been 34.4% low on refrigerant over a four year period and that could have been your only problem. These losses are okay with the EPA, but you don't dare release a gram as a technician. We don't either design these systems nor make the rules.

mak11 on Wed August 20, 2008 9:24 AM User is offline

I conducted an experiment and added some more refrig.
I kept adding refrigerant little by little until finally I let the high side reach 450 psi.
Finally the high side got so hot that it blew the that gauge hose off the coupler that was hooked to the line.
My low side all the while stayed in proper range as Tim posted above and still no cold lines even behind the orfice.
Thanks for your thoughts on the matter.

GM Tech on Wed August 20, 2008 9:47 AM User is offline

Unless I missed it-- are your cooling fan(s) working? with a/c request?

The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

NickD on Wed August 20, 2008 10:26 AM User is offline

For a small car, really a very large condenser, about 28" across and 22" high, with a tiny single 8" fan off to a corner. Wasn't very wise to let that high side go much over 300 psi, trying to kill yourself? Either your orifice is not properly seated or you have air in the system, and in a 24 ounce system, doesn't take very much air to skyrocket the pressures, but this was already suggested before.

mak11 on Wed August 20, 2008 12:36 PM User is offline

The cooling fan for the air conditioner woks fine.
One thint that's different now that i recharged it is that originally when I first got the car, the compresser would cycle on and off about every 5 seconds, but no cooling.
Now the compresser stays engaged with no on/off cycling, but still no cooling.
Thanks again for your comments.

NickD on Wed August 20, 2008 1:36 PM User is offline

Only thing that would cycle the compressor is that dual high side sensor, if the refrigerant was low, would cause that cycling, would have checked for leaks, but also very valuable to learn how much refrigerant was lost to learn the severity of the leak.

Let's say it was learned that 9 ounces of the refrigerant was lost, certainly drastic enough to cause major cooling problems, but on the other hand, only a couple of ounces per year. Would have just topped it off and see what happens and probably replace the port caps as those crazy R-134A couplers have a tendency to leak, should have stuck with the old Scharder type as they are super easy to repair and could have used a different thread. That neoprene gasket especially in the high side cap gets hot and loses it's flexibility.

The next question, did the system lose any oil? That is of prime importance requiring a very careful inspection of the system, could let that go or inject an ounce of the same oil the OE used on an untouched system.

Ironically, seeing a lot more leaks with these new systems with all this EPA crap they started, jumping all over the techs, but letting the OE's go scott free.

Matt L on Wed August 20, 2008 2:05 PM User is offline

Where, relatively, do the high-side service port and the pressure transducer sit in the system? Your compressor should have shut down before you blew that hose, unless there is a restriction between those two parts.

GM Tech on Wed August 20, 2008 3:36 PM User is offline

Your system DOES NOT CYCLE by design-- if it is-- then you have either the radiator/condenser fans inop- or a massive restriction., or an overcharge. Variable compressors do not cycle when they get low on refrigerant.. period-- the refrigerant pressure transducer sensor (in front of condenser on high side line) is seeing high pressure and shutting down the compressor to keep from blowing the high pressure relief valve.

Since the transducer sees it and your gage sees it- then your problem lies in the inability to pass refrigerant through the condenser--

The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

NickD on Wed August 20, 2008 4:25 PM User is offline

It will also shut down on the low end just as well as the high end, for a normally operating system, an ambient temperature of less than 38*F will stop the compressor that translate to about 37 psi. That green light in the climate control panel is kind of dumb, will stay lit if the temperature drops to 40 below, but the compressor is not running. That's because it's switched either by the mode switch in the recir or defrost position, or the compressor switch before that voltage goes into the PCM that also has the pressure transistor feeding the PCM to control the AC relay. Been thinking about moving the hot side of that lamp wire to the compressor for a proper indication, but too much work and with that four banger, can hear and feel when the compressor is operating.

Can visualize a situation when the compressor kicks on the high side pressure will drop below the 37 psi level to cut it off, then static pressure will rise to kick it on again. But here the problem is low charge, very low charge.

mak11 on Wed August 20, 2008 4:38 PM User is offline

I think your right that its somehow its not getting through the condenser,
But a thought hit me that could the dryer somehow be blocking thing up instead of the condenser but if that was the case then the line going into the evaporater would have been more than lukewarm due to higher pressure backed up there.
This is one time I wish there was away to test the pressure just before the orfice tube.
I may just have to go ahead and replace the condenser and the dryer.
Thanks again for the input.

mak11 on Wed August 20, 2008 4:48 PM User is offline

Do you think my refrigerant pressure transducer sensor could be the problem somehow?

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