Where's the A/C Experts? Need help..... Again.

LDC2335

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Fellas,

I replaced every component of my a/c about 2 years ago and had it tested and recharged at a local shop. It has never been quite right though. I think it's just a matter of taking out or putting in some refrigerant to get the pressure just right, but it seems that adding some causes the compressor to not cycle and stay on, and therefore the air doesn't get cold. And when I take some out, it cycles too fast and air still doesn't get cold. The low and high pressure switches are brand new.
in this video, I have the throttle at about 1200 or so and the can is not open, I was just using the gauge on it.

When it is colder outside, like in the morning, it gets very cold, and then in the afternoon it gets warm out and the air is colder than ambient, but not ice cold as it should be. I can feel the compressor cycling while driving, maybe slightly faster than I feel it should.

Could the intercooler be blocking enough of the condenser to affect the air temp? I wouldn't think so as my engine temps are fine.

Any ideas? Is this cycling faster than yours? The part I don't get is that the low pressure switch is on/off at 25/45 psi-ish, so when the outside temps go up, so does the pressure and then it throws everything off. Seems like every season, I am re adjusting it slightly.

Take some out? Put some in? I just have nothing to compare it too.

Compressor cycling: http://youtu.be/Wq9_q3lC2Oo
 

crazycarlo

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My intercooler blocked mine and would make my AC not perform up to my standards. In fact that's one of the reasons I switched to the eaton setup onc my car. Also I never broke my AC lines open and when I made the switch it worked great again.
 

ZeroDCX

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You need a Manifold Gauge Set to see what High Pressure side readings are. But more than likely you're low on refrigerant. If the system is low, then it will turn off to prevent damage when low side pressure drops below threshold as the compressor turns on. It will rapidly cycle as the low side pressure builds back up and lowers again. Hence the rapid compressor clutch cycling. My car did the same. I purchased a manifold gauge set and saw that overall system pressure was a lot lower than it should have been. Filled it to proper specs and all has been well since then. (This was over a year ago though, so I can't recall proper specs for high side and low side pressures).

To answer your question though, yours cycles much faster than normal. Also readings will vary depending on ambient temperatures and if the engine is hot/cold.
 
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LDC2335

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Thanks, maybe autozone will have one. Just sucks, I had to bend the high side hose for the supercharger, so it's way under the power pipe.
 

SnakeBitten07

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I agree with ZeroDCX. A set of gauges on a manifold are a must - the factory service manual should specify proper pressures based on ambient temperature. If you don't have an FSM, I can check mine at home.
 

LDC2335

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I don't, so that would be great. I have a Haynes manual, but it doesn't list them.
 

NELCO

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Technically, the refrigerant charge should be weighed in to factory specs. With the gauges you should be able to get real close.
 

DSG2003Mach1

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If there's s harbor freight around find a 20% off coupon in a magazine and you can get a decent enough set. If I recall low side shouldn't exceed 60psi with compressor running and high side around 2.5 times outside temp for a ballpark range
 

LDC2335

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At 60 psi the compressor should be off and shouldn't cycle since the low side switch turns it off at 45 and back on ehen it drops to 25.
 

DSG2003Mach1

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that doesnt sound right. When the compressor is off, the pressure between low and high side equalizes. The compressor will kick off if the low side falls below a certain pressure but I dont have that # handy. Then with the compressor off, low side pressure rises triggering the compressor to kick back on again, low pressure starts falling and the cycle repeats.

I believe the high pressure cutout only applies to the highside of the system, I dont think the compressor will cut off if pressure on the low side goes too high, otherwise it would never let the compressor start. When the car has been sitting you will definitely have over 60psi on each side with a properly charged system
 

LDC2335

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I borrowed a manifold gauge set from autozone,but I was not able to get a high side reading. I don't know if my nipple is broken or the gauge was broke. I was able to add some refrigerant and get the low side up to the 50-60 psi range at about 80 degree outside temp. Air is ice cold. Hopefully I dialed it in close enough to not have any more trouble.

Thanks for the input.
 

SnakeBitten07

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Sorry for the delay, but here's the temp/pressure charts, along with the fan cycle charts you need to get your pressures right. The second chart from the top shows your high and low pressures as a function of ambient temp. Try to use a thermometer close to the evaporator, but not in the air flow.
IMG_4437.jpgIMG_4438.jpgIMG_4439.jpgIMG_4440.jpg
 
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LDC2335

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Awesome, thanks man, doesn't get much better than that!

Looks like I my be a tad over.
 

SnakeBitten07

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No problem. In my experience with A/C systems - I pressure this exactly as the charts describe, because even a tad over will lead to excessive cycling when ambient temps get hot.
 

LDC2335

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^ that's why I f'n love this site.

Good dudes, good info. Thanks again. My a/c is running great. Knock on wood.
 

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