Engine Size: 5.7
Refrigerant Type: R134
Ambient Temp: 100
Pressure Low: 55 psi
Pressure High: 50 psi
Country of Origin: United States
So the front Air A/C never worked right but the rear A/C was fairly cold. I thought that there was something else causing the front A/C not to work (blend Door).
I was unable, until the other day, to confirm that was the problem, so my step-father was helping me try and figure out what was wrong with it, he had one of those Autozone freon kits that has a small dial gauge attached to the can and he said it needed a little freon, but still no avail. Now the rear air also doesn't work. After much reading and a new set of gauges i found that the low-side is about right for a 100 degree day but the high-side is extremely low @ 50. My thought is that the Orifice tube is clogged. ( Blend door works correctly) The site glass also doesn't show anything flowing by. Also there is a buld off of the High-side that gets VERY hot and the bulb on the low-side is also hot but not as hot as the high-side
My next problem is that i was attempting compare a known good ( 05 Nissan Sentra 2.5L ). The Nissan's A/C Works Good so i checked the Stats from the Nissan against the Suburban stats and the Low-side on the Nissan was extremely high over 120 psi and the High-side was 150 psi but this time there was fluid flowing by the site glass.
Thanks in advance for the help, if there is anything i have left out i will be glad to get more info
First, in order to measure pressures, always close both handwheels on the manifold. And ignore the sight glass on the manifold under all circumstances. The more expensive professional-grade manifolds don't have a sight glass.
Readings on the Suburban show that it is basically empty, most likely the result of a fairly major leak. "Static" pressure (meaning the pressure on both sides with the engine off) should be over 100 on a hot day.
Edited: Wed August 12, 2009 at 10:50 PM by mk378
Mk378, thanks for the help!
I tried to add freon but the low-pressure side ( with an autozone refill kit with gauge) showed the pressure rising above 60PSI and until i got the gauges had no way to test the high-side. So should i ignore the (seemingly abnormal) rise in pressure and continue to try and add freon? What about oil in the system should i be concerned with the level? If so how do i test it? Thanks again
Edited: Thu August 13, 2009 at 12:38 AM by Iz3k34l
If the R134a refrigerant (yours doesn't use freon, which is R-12) is that low, you have a leak. You must fix the leak or you're wasting your time (and money) and probably violating environmental laws.
1. Find and fix leak.
2. Pull vacuum with vacuum pump.
3. Add correct amount of refrigerant using correct gauge set.
What are the most common culprits that would leak? I ordered a vacuum pump and should be getting it in the next week. I have given thought to evacuating the system and just starting from scratch. probably the best thing to do.
Don't evacuate it yet !
Beg/steal/borrow a leak detecter first. Unless there is an obvious leak - oily marks on a hose etc. then it will be very hard to find the leak once the system is empty.
You can use Nitrogen to pressurise an empty system in order to find a leak, but very few Do-it-Yourselfers have that laying around in the garage.
Vic @ Pennine AutoChill
I had a similar situation, however I think I knew a little more about MVAC than you at this point and I had a friend that was knowledgable.
I had charged my system up and in three days lost the charge. Pressures were 25-30 low/50 high. Obvious leak in system. So, recharged system adding a can of leak detecting dye into it. In another three days, cooling was going away and the OBVIOUS Leak appeared in the compressor, bad belly leak.
Replaced compressor, accumulator and OT. Vaccummed, recharged and WALLA!!! System cools fine and no more leak...
Not to say your compressor is the leak culprit, but the dye will show you were it is, especially if it is that serious...
was there any sealant in the Magic bottle of R134a from Autozone?
actually there was some leak sealant in the magic can. Its the R134A with sub-zero, claims to stop leaks.
Ok the leak detector arrived today but i couldn't locate any leaks. As far as pressurizing the system can you use compressed air. Any suggestion and help is greatly appreciated. THANKS!!!
What model leak detector are you using?
It was an Ebay cheapy
Edited: Tue August 25, 2009 at 6:26 PM by Automotive Air Conditioning Information Moderator
Most common leak spot on those is the compressor itself, check for signs iof dye (a UV light would help) around the halves of the compressor.. and oil/dye around the seams is a leak... If you have a belly leaker, ask the guys at Ackits.com about there replacement clones.. I have a seltec on my truck, been working just fine for three years now...
Freedoms just another word for nothing left to lose
When you go to leak detect a car, first sniff around the service ports with the caps on, there should be no leak. Then take one of the caps off, there is invariably some refrigerant trapped under the cap. Hold your detector there as you remove the cap and it should register a very solid "hit". If not, the detector is probably not working.
Thanks, sorry bout the link i placed it to show the leak detector unit i bought, anyway i have no obviously visible places of leaking. I tested the unit by taking the cap off the low side and there was some green residue from when i had checked the pressure and the leak detector picked it up. I then cleaned the green dye and checked it again and it didn't detect anything. Thanks
I would imagine that the sensitivity is not that crisp with a cheap leak detector. So while you register with heavy residue you may not find a slow leak.
it does have a sensitivity level dial ;o) , but what about pressurizing the system, would that help to be able to detect a small, slow leak?
I always check a system with a full charge unless there is an obvious sign of a leak which need repair. I've had and seen tools with all sorts of buttons and bells and they still did not work!
My problem is trying to charge the system is that the high-side is low while the low side is about right. My thought is the OT.
If that 55 low 65 high is with compressor running- then your pump is history--- see if compressor turns very easily, with one finger, and/or has little "catches" in it as you rotate it-- if so you have the dreaded suctione reed failure-- and definitely need a new compressor...
you could have just quoted the pressures-- that huge photo is hard to deal with....set your camera to a smaller size picture setting please.
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......
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