AC Question

[kens04]

Have had a 2004 3.5L Vue for the last 7 months. Live in Florida so the AC runs most of the time. Recently noticed that it is not as cold as when I bought it. Noticed that at a light or at idle, it goes warm and when on the highway it is cold but not really cold. Pressure on the low side is erratic and around high at 55-65 PSI at idle and goes to 40-45 PSI when RPM is between 1500 and 2000.

Had the system evacuated and refilled with the same results. Mechanic believes a reed valve in the compressor is stuck or damaged. Anybody else ever experience this? The system has not been open to the elements. I'm ordering a new compressor with the hope of just changing it and recharging the system.

Anything else to check or watch out for ? Inputs appreciated !!! :)

[fdryer]

40 psi ~ 34-35F, 45 psi ~ 40F.............temperature/pressure chart for R134a

1-Did any one note the surrounding temperature/humidity, car interior outlet vent temperature when the a/c pressures were measured? The interior outlet temperature at medium fan speed would be compared to surrounding air temps for a temperature differential against the relative humidity to assess the overall cooling of your a/c system.

2-Have you or anyone ruled out the blend door being stuck and allowing heater air to mix with chilled air? Our vehicles no longer have a heater shutoff valve and run HOT coolant 365 days/yr through the heater coil and the blend door is the only way to block off heated air from mixing with a/c chilled air.

3-Buy a small dial thermometer to insert into the center vent to monitor the chilled air, whether you're stopped or moving. Be sure that the front condenser coil isn't blocked and the cooling fan is running when the a/c is on. Approximate interior temps should be around 45F or less after 10 minutes or so of road driving on medium fan speeds. At a standstill, depending on whether an external fan is blowing supplemental air into the front of the car, the interior temps should be around 45F also, windows up and preferably in the shade.

There are many factors that go into determining why your Vue no longer cools as it did when new and its just guessing at this point. There are several reed valves in a compressor and if one were faulty there won't be any differential pressure between the suction and pressure side. If you understand how a reed valve works then you'll know that it operates as a simple one-way valve to keep the high pressure output from returning back into the compressor's suction side. A compressor is an expensive guess if you're wrong. There is the expansion valve and filter/drier to consider as possible faulty components. Overfilled the system that doesn't allow the expansion valve to operate as designed? Has anyone injected sealer into the system? Sealer can interfere with a/c operation and detrimental if used incorrectly.

[VTchemist]

I agree with Fdryer, there are a few more things to check first

I had problems with my dryer assembly. There was a very small crack in the metal housing for one of the hose couplings. I had the dryer and hose replaced. All has been good since then.

You mentioned the system had not be opened. That's good, for lot's of folks will go the the local auto store, buy a can of R-134a with a sealant, and try to fix their AC. Then, the expansion value gums up with the sealant.... bummer...

Did your mechanic check throughly for leaks in the hoses and couplings?

If they put a new compressor in (and it does not fix the problem), I'd ask them to refund your money for the labor and filling of the system. You'd just pay for the cost of the new compressor. Make sure you have it in writing.

[kens04]

I can provide more information .

Outside air was 82F. Humidity don't know - 55% ? Dry for Florida
AC set at Max Cold and Recirculate. Windows closed.
Temp at the vents - 65F at between 1500 and 2000 RPM
Temp at idle 72F

Bought the car used. There is yellow die in the Freon. Don't know if this was done after new or is this Saturns intitial charge.

Had the system evacuated and recharged with 1.7Lbs of R134 yesterday.

Oil is leaking from the compressor. Found this after the refill...my bad. My experience with R134 on my other cars up to this point has been to evacuate and recharge and all is fine with them.

Borrowed a sniffer from work and checked the lines. Only goes off near the compressor so I'm guessing I should start with it.

Also, noticed that once the AC hs been run for awhile and you shut down the engine, you can hear and feel the compressor buzzing like pressure is being relieved on the low pressure side. sound like a fan running for about 20 seconds.

Since I already have the compressor on order, should I also get an expansion valve? I can replace both before I have it recharged.

[fdryer]

I can provide more information .....Bought the car used. There is yellow die in the Freon. Don't know if this was done after new or is this Saturns intitial charge.....Oil is leaking from the compressor. Found this after the refill.........my bad. Borrowed a sniffer from work and checked the lines. Only goes off near the compressor so I'm guessing I should start with it.

Since I already have the compressor on order, should I also get an expansion valve? I can replace both before I have it recharged.

No expansion valve necessary since you found the source of the leak; the compressor. When replacing the old with the new one be sure to use new O-rings, measure the oil drained from the old compressor to ascertain the amount needed to fill the new one, and be sure of absolutely no more leaks when evacuating the repaired system. After evacuating the system and seeing 29.99in. HG on the vacuum gauge shut off the vacuum pump off, close the manifold valves and wait at least ten minutes to see if the vacuum holds otherwise you still have a leak somewhere; the manifold gauges, hoses, fittings, another source of leaks. There must be absolutely no leaks when a vacuum is established before continuing to be certain that you'll have a sealed system again just as it was when new from the factory. If no more leaks exist then finish the evcuation to rid the system of any moisture before injecting R134a. Hopefully you'll have cold air right in time for Florida heat! :cool:

When you examine the drained refrigerant oil, check for any debris otherwise consider replacing the filter/drier. Its the cheapest insurance to ensure a clean system that filters out any remaining crap that can hurt system performance by lodging in the wrong places like the reed valves and expansion valve. You're performing a major repair so its worth the initial high repair costs as your car is relatively new to assure a long life.

[kens04]

Thanks for the input.

I forgot to mention that at idle, both the low and high side pressure needles danced up and down in sync with the RPM. When the RPM was increased to 1500 to 2000 RPM they stablized but were flakey. Kind of confirms my thoughts that the problem is RPM /compressor related.

Will have the new compressor installed sometime next week when it gets here. Have parked the car in the garage until then. Will let you know the outcome.

[fpkites]

Sounds like you've hit the nail on the head after you saw juice at the compressor - definitely get that changed out so you're not venting expensive freon (well, relatively expensive :D)

Also, my experience with FL is bugs, and lots of them. Did you spray air and water forward through the radiator/condenser to clean out the guts? Constricted airflow can cause cruddy AC as well.

[kens04]

Well got it into the shop today. New compressor from DiscountACParts.com with O Rings. Evacuate, flush and recharge.

Ice cold air...... 46 degrees at the vent at an idle.

We are ready for summer !

Thanks again for the help. :D