A little background first. my compressor failed 6 months ago (clutch assembly) so nothing in the AC system failed, no catastrophic compressor failure. I didnt want to pay the $1000 price tag i was quoted to fix this so i did ALOT of research on AC systems. With all the research i did, i was able to replace my compressor/accumilator and orifice tube as per most the instructions i found saying to do this when opening the system to atmosphere. I also installed a inline filter that was recommended by all the reading i did. I flushed the system and blew dry notrogen through it. After this everything worked and i had no problems. about 3 months later i started getting condensation on my windshield and a whoooooshing sound coming from the HVAC system. I recharged the system and it worked for about a few hours then started doing it again. After troubleshooting the system, the whooooshing sound was coming from the orifice tube. it sounds like air blowing through an airhose nozzle. Yesterday i replaced my orifice tube and accumilator, charged the system to 30PSI on the low side and i still have this whooooshing sound coming from the new orifice tube. When i removed the system yesterday, the oil looked good (not black). I spoke with the A/C mechanic and he is lost also why my orifice tube is making that sound.

So i need some help here, what is causing my orfice tube to do this and why. Other then the sound, everything works. I have cold air coming out of my vents and the system is working as it suppose to. No leaks and its maintaining pressure. This is why i am asking for expert help from someone on here.

Thanks

 

did you pull a vacumn to-29in. close off all valves. see if system holds a vacumn. if not you have a leak. apply small dry nitrogen charge (30) psi. check for leaks, use bubble soap, did you measure the oil charge.

 

the A/C tech pulled a vacuume on it said it was holding just fine. I dont know to what -bar he pulled it to. I dont think i have a leak because it is holding positive pressure in the system since i charged it yesterday

 

if it is leaking down" IT DEFINATELLY HAS A LEAK " pull vac., let it set for around 4 hours, if it holds ok, if not you do have a leak, maybe even over serviced with oil, i don't want to step on toes, but it doesn't hurt to double check, borrow a vac. pump and do this yourself, hope this helps.

 

That would be my question too...how long did he pull vacuum on it for? 2 minutes? 2 hours? Just because it holds at 2 minutes, doesn't mean it will hold for 2 hours, and if it doesn't hold for 2 hours (as above said), then you have leak.
I also agree that too much oil in system could be potential problem...do you know how much was placed into system? Did you add oil to compressor by pouring in? Or did you use the can charge oil?

 

I prefer to set mine on the pump overnight. If it will hold 500-microns then it won't likely be any better. Have found several small/slow leaks this way.

AUTO A/C FORUM is the best place, IMO, for your question.

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i think autozone rents vacuumes here, i will give that a try. If there is a leak, i am thinking it is the inline filter i put on it. When i installed it, i didnt like the way it installed. It didnt call for flaring the ends, it was a compresson fitting with a rubber sleeve. It didnt look right to me. I will do the soapy water thing also this week to see if i can find a leak.

The R-134a was a premix oil/freon mixture. Its what the tech told me to use. Also when i installed the compressor the instruction that came with it said it was already pre-oiled and i just needed to manually rotate it 10-12 times. Since i used a premix freon/oil, is there a chance there is too much oil in there?

 

There is a slight chance you may have too little oil! The receiver dryer (accumulator) can hold quite a bit of oil and there should be a spec that tells you how much oil to add for each component replaced. Most R134a is premixed with a flourescent dye. Find a "black light" and check all the hoses, connections, fittings, condenser, orifice tube, and the drains under the truck for signs of dye. If you find dye on a drain line, you may have a leak in the evaporator/plumbing inside the heater box. Once in a while, you will get a system that will hold a vacuum but still leak under pressure. Vacuum is measured in inches of mercury (-21"), pressure is psi (around 275psi on the high side). Also be advised that too much R134a may cause the A/C system not to cool down due to excessively high pressure. The high side temp/pressure switch cuts the compressor out when either gets too high.

 

update: I rented a vacuum and it held vacuum over night. Then charged it and it has held charge for a week now. filled it with some ultraviolet die and cannot find any trace of a leak. Scanned the entire system but the evap core. I still have the sound coming from the orifice tube... talked with another AC tech and he also is completely lost why it does it after everything i have done with the system. but said he could fix it for $1200.

sooo...what could be next?

@Sur5er - i filled all the replacement parts with the required amount of oil as per the AC sheet i have.

 

Under normal conditions never add oil. Your precharged compressor has enough for the system. I prefer to run vacuum pump for about an hour and make sure it holds for several (if I'm working on my own stuff, customer stuff You can't bill the labor so you gotta go and take a chance) hours. Depending on your altitude is all the inches of vacuum you will get. Dye is great but problem is the molecules in teh dye is larger then the molecules in the freon so you can have a leak and dye will never show up. Best thing to look for is oil on the lines, high psi line from the compressor to the condenser will be the most likely spot for a leak. To much oil will cause just *** bad of problems as anything. Let me know if you need any help, I have been doing a/c work since 1993.

 

from my own experience, if the compressor comes precharged, and you followed the instellation instructions. you would install r134a unoiled, if you put in r134a +oil you have over oiled the system, the excess oil will restrict the orfice tube operation, the charge will have a foaming effect, i don't believe you need new parts, vacumn the system to remove some of the excess oil, a proper vacumn pump will have container to measure the oil being evacuated, a system will work with lower oil capacity just fine .

 

when you installed the compressor did you rotate it in the proper direction? moving the oil in the proper direction, if not you could of hydraulic locked the compressor, causing damage to the pump. when under pressure it can't hold high pressure

 

it sounds like i might have too much oil in my system. What would be the best way to get excess oil out of the system if the vacumm doesnt get enough?

@smokinwrench&gcssr - when i vacummed the system earlier this week to check for leaks i didnt put R134a+oil in there, only after i replaced my orifice tube and accumilator did i use the R134a+oil. the last charge i did was just plain R134a.

@gcssr - i made sure i rotated the compressor in the right direction. But as my original post states, everything works fine. i maintain pressure, the compressor cycles on and off and i get cold air blowing out of my vents. The line to the condensor is hot while the exit line is cool. there is condensation on the accumilator. So everything in the HVAC system works as it suppose to, with the exception of the sound the orifice tube is making.

 

It sounds like you need to go back to basic's. If the system was not properly evacuated, you have moisture in the system. probably need to clean system, new dryer/accumulator, clear all oil, drain the compressor, and service the oil, per the manifacture specs. vacumn system to -29in (all the vac. pump will evacuate, leave pump running for two hours.) the vacumn will dispell any moisture in the system, important that no moisture be trapped in the system. yes i would replace the orfice tube (inspect old tube for damage to screen /seals ) what kind of inline filter, this function is normal function of dryer/ acc. LEAVE VAC ON THE SYSTEM FOR ANOTHER 2 HOURS AS A LEAK CHECK (pump off)

do a google search for help. Grant