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A/C performance woes... #4109246 05/28/16 08:49 PM
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SEMI_287 Offline OP
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Well warm weather is upon us in upstate NY. My 300's ac performance.. well.. sucks to say the least. My buddy evacuated the system, pulled a vacuum for an hour and recharged to 1 lbs 8.5 oz, which is just a hair under the 1.628? pounds of R-134 it takes. When it was in the 60's and 70's it worked great. There were a few times going down the road you'd get a blast of not so cool air then it would go back to ice cubes. Fast forward today I was on my way home from work and it was barely cool. Ambient temp was around 92F. After driving at 60 for about 30 minutes it would cool down but as soon as I stop it would blow warm. Start driving and it would cool down again. That was very annoying for a 3 hour ride.

Once I got home I let it idle for 10 mins on max ac. It was barely cool in the car. The fans are working, both are churning on low and kicking up on high. The low side is COLD and the high side is HOT like it should be. I threw my gauges on it, well just the high side. I could NOT get the service cap off the low side, my buddy tightened it very tight and it's not very easily accessible. The high side read 250 psi at idle or 2000 rpm. I drove my wifes Avenger around and her ac is ice cubes regardless of speed. When it cooled off tonight it worked find at speed but was still warm at idle.

What could the cause of this be? I don't think the condenser is faulty because the suction line is very cold and the discharge side is hot. Do you thing that the expansion valve is starting to go out? I might add the compressor isn't cycling, it's on all the time.


2013 Hyundai Elantra- Valvoline Synpower 10w30, Champion
2005 BMW 325xi- M1 0w40, K&N
2007 Chrysler 300C- M1 0w20, Wix




Re: A/C performance woes... [Re: SEMI_287] #4109254 05/28/16 08:54 PM
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HerrStig Offline
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Your receiver/drier may be failing internally and clogging the expansion valve. It seems to be standard policy to replace it when doing a full recharge.

Re: A/C performance woes... [Re: SEMI_287] #4109258 05/28/16 08:59 PM
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29662 Offline
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Could very possibly be the condenser. The internal passages on modern condensers is astonishingly small. They clog very easily, and many manufacturers recommend replacement.

Re: A/C performance woes... [Re: SEMI_287] #4109261 05/28/16 09:01 PM
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artificialist Offline
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How much junk is clinging to your condenser and your radiator? It would be wise to spray the back of the radiator and condenser with a garden hose.

Does the blend door move the way it should? Sometimes it will stick in a position where it will let both air from the heater and from the evaporator and lower the effectiveness of the A/C. If there is a sensor in the ventilation ducts, it would interpret the air as not being cold enough to cycle the compressor off, explaining the lack of compressor cycling.

Does your car have all electric fans, or does it have one that is clutch operated? Sometimes the clutch will work okay at idle, but fail to keep ur as RPMs rise.


2010 Lancer Ralliart Sportback
Re: A/C performance woes... [Re: SEMI_287] #4109267 05/28/16 09:12 PM
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mcrn Offline
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Condenser fan not working properly?


2012 Nissan Rogue
Re: A/C performance woes... [Re: artificialist] #4109273 05/28/16 09:15 PM
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SEMI_287 Offline OP
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Originally Posted By: HerrStig
Your receiver/drier may be failing internally and clogging the expansion valve. It seems to be standard policy to replace it when doing a full recharge.


I hope it is the expansion valve and drier, it's very easy to get to both and they're cheap.

Originally Posted By: 29662
Could very possibly be the condenser. The internal passages on modern condensers is astonishingly small. They clog very easily, and many manufacturers recommend replacement.


While the condenser can be had very cheap, you have to take the front bumper off to replace it. Not fun, I hope it's not the condenser.


Originally Posted By: artificialist
How much junk is clinging to your condenser and your radiator? It would be wise to spray the back of the radiator and condenser with a garden hose.

Does the blend door move the way it should? Sometimes it will stick in a position where it will let both air from the heater and from the evaporator and lower the effectiveness of the A/C. If there is a sensor in the ventilation ducts, it would interpret the air as not being cold enough to cycle the compressor off, explaining the lack of compressor cycling.

Does your car have all electric fans, or does it have one that is clutch operated? Sometimes the clutch will work okay at idle, but fail to keep ur as RPMs rise.


Visibly it looks clean, may be worth taking the hose to some day. The fans (which are electric and functioning normally to answer your last question) are easy to remove. An electrical connection and 4 bolts. Blend doors are fine, no noises and I can get full heat and ac anytime.


2013 Hyundai Elantra- Valvoline Synpower 10w30, Champion
2005 BMW 325xi- M1 0w40, K&N
2007 Chrysler 300C- M1 0w20, Wix




Re: A/C performance woes... [Re: SEMI_287] #4109297 05/28/16 09:40 PM
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DerbyDave Offline
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I had a Jeep Cherokee about 9 years ago where the AC would work for about 10 minutes and then warm air. It didn't leak and the refrigerant charge was full. The Condenser was beat up from many many highway miles. I replaced the condenser, receiver / drier and the expansion valve and afterwards you could hang meat in that thing.

Last edited by DerbyDave; 05/28/16 09:41 PM.

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Re: A/C performance woes... [Re: SEMI_287] #4109368 05/28/16 11:23 PM
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DoubleWasp Offline
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You have a restriction somewhere in your system.

Toss the drier/accumulator, condenser, and expansion valve.

Flush the system. You'll be amazed at what comes out.

Modern condensers are un-flushable. Stop beating around the bush and toss the old girl.


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Re: A/C performance woes... [Re: SEMI_287] #4109380 05/28/16 11:39 PM
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I need to know what the low side pressure is at idle.


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Re: A/C performance woes... [Re: SEMI_287] #4109427 05/29/16 02:26 AM
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mehullica Offline
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Without both high & low side pressures at idle & 2500rpm you'll never know what's wrong. You'll just be throwing parts at it.

Re: A/C performance woes... [Re: SEMI_287] #4109448 05/29/16 05:32 AM
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SEMI_287 Offline OP
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When it gets good and warm I'm going to get both sides measured. The low side service port is between the engine and shock tower facing the ground...


2013 Hyundai Elantra- Valvoline Synpower 10w30, Champion
2005 BMW 325xi- M1 0w40, K&N
2007 Chrysler 300C- M1 0w20, Wix




Re: A/C performance woes... [Re: SEMI_287] #4109542 05/29/16 08:23 AM
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mk378 Offline
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Originally Posted By: SEMI_287
The low side is COLD

That means the refrigeration loop is WORKING. The air leaving the evaporator would also be approximately that cold. Something is wrong under the dash causing it to reheat the air when it shouldn't because you have the controls set for full cold.

Re: A/C performance woes... [Re: SEMI_287] #4109557 05/29/16 08:45 AM
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I had a truck once that would do the same thing. It turned out to be the compressor clutch. It was worn to the point that when I stopped it would disengage but accelerating made it catch again. This was on a rear wheel drive truck though but still something to look into.


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Re: A/C performance woes... [Re: SEMI_287] #4109638 05/29/16 09:59 AM
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Jetronic Offline
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can you bypass the itnernal heater and loop the coolant in the engine bay? if the AC works as it should then, you know you have to look inside the cabin... or, disable the mixing flap if you can reach it, so there's no way hot air can be mixed in.


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Re: A/C performance woes... [Re: SEMI_287] #4109766 05/29/16 01:24 PM
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sleddriver Offline
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I was thinking compressor clutch slipping as a maybe, but then again 2007 isn't that old really.

If you do lots of HWY driving ("3 hr ride"), you might benefit from a thorough external condensor cleaning. Is it clogged with bugs? Cheap, sudsy ammonia works great at dissolving dried bugs. Spray on a 50/50 mix and let it work about 8 min. as it needs to rehydrate them first before disassembling the proteins. Flush with water and repeat.

When you update your gauge readings, we also need the ambient & dash vent temps.


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