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System won't accept freon

needthatair on Mon June 29, 2009 10:13 PM User is offline

Year: 1996
Make: GMC
Model: Suburban
Refrigerant Type: R134-A
Ambient Temp: 90
Country of Origin: United States

Evening all,

Same ole story....the AC doesn't work....and it's summer.
A bit of history: New compressor along with multiple other components last summer. Thsi was as a result of the techician who let pieces of the old dryer contents pass through the system and burn up the compressor if I remember correctly. It is a dual system for front and back.

Latest problem:
Initially, the compressor began to cycle. Compressor does opporate. Air blows hot. I've done guage readings and they are equal at about 85 psi on high and low side. The quick connect charge status guage indicated in the RED danger zone when taken from the low side.
I tightened the schreader valve on the low side, because I thought I heard a bit of pressure escape when I removed the protective valve cap from the low pressure side.

I stopped at a AC service center and the guys did a recovery on the system and said that it only had 2 tenths of 1 pound in the system.

I attempted to charge the system with 64 ounces (4.6 lbs) as recommended and was only able to get one can in before it stopped accepting any more contents. My manifold guages, both high and low still read 85 psi with the system on or off. We have had a problem with the wet carpet on the passenger side under the dash, and when I attempted to open that cover ans such up, I realized I was getting into a big project than I should without knowing what I was doing other than reading from a AC repair manual.
Any suggestions would be greatly appreciated.

torque395 on Mon June 29, 2009 10:27 PM User is offline

Maybe the high/low pressure switch(s) are bad? 85psi should be enough to run the compressor for sure.

1996 Chevy Suburban 2500 4x2 6.5L Turbo

mk378 on Mon June 29, 2009 10:49 PM User is offline

Clearly you have a leak. It is normal to have some pressure under the cap when you unscrew it. I suspect the leak is somewhere else.

Did you start charging from a full vacuum? That is important.

The compressor should be engaging with 85 psi pressure. If not, it may be because many GM vehicles have a "lock out" to protect the compressor. After detecting a severe undercharge, the PCM will refuse to engage the compressor any more. This can be cleared by disconnecting the battery (with the key off) for a while.

Chick on Mon June 29, 2009 10:51 PM User is offlineView users profile

Did you pull a deep vacuum and charge into the vacuum? I think you should recover the refrigerant in there, pull the O tube from the front and check for debris, then find and fix your leak if it's clean.. If not post back with what you find.. But you do need to change an empty system into a vacuum, air in the system will not help, but will destroy the system due to high pressures, also you need both high and low pressures when trying to diagnose the system..hope this helps..

Email: Chick


Freedoms just another word for nothing left to lose

needthatair on Tue June 30, 2009 12:12 PM User is offline

The compressor was initiating and began to work when I dumped the first can in the system (or atleast I could see the clutch kicking in and functioning) but of course no cold air yet (i gues because the system was less than about 25% full...?)

No I did not pull a ful vacuum as I had wanted to. I tried to pull one initially through a little compressor driven venturi tube type vacuum unit, but did not have the correct valve on the end to close and see if the sytem held the vacuum, so it all blead off. I was told by a guy at the local parts house to bleed off the 2/10ths of the remaining pound of freon in the system and start filling from there...which was what I did. I know I should have vacuumed it down, but it was late at night, and frustrated with the problem of not knowing where to go or what to do...I just tried to fill it and see if it would hold a charge for any period of time to get us by in this heat wave.


needthatair on Tue June 30, 2009 12:14 PM User is offline

I'll try that.
What is the "O-Tube"? there another name for it?
I am using the Haynes AC service and repair publication as a reference and don't recall anything in it about the O-tube.

Thanks for the time and help.

Chick on Tue June 30, 2009 6:20 PM User is offlineView users profile

You need to remember most "parts houses" as you call them know nothing about AC service, just selling anything you want to buy, so really, please don't follow their advice, not even for what wax you should use on your car, keep that a personal choice.. Now, you need to pull a deep vacuum, add back the proper amount (on the underhood label) by letting the vacuum suck in as much as it can thru the high side WITH ENGINE OFF!!! then close the wheels to the high side and finish by starting the car and filling thru the low inside until you have the proper amount in there, then check your pressures, let it run awhile check for leaks (visible or dye light if you have one) A good spot to check on those is the seams of the compressor halves, we call them belly leakers.. Do a search on the forum for belly leakers and you're sure to see a pic, or I can add one if you can't find one.. Next would be the high side service port, and in any case, make sure you use caps on the ports and that they are tight..Let us know how it is after you recharge it correctly, along with pressures and ambient temp.. Hope this helps..

The O tube is the expansion device located at the inlet of the evap or outlet of the condenser depending on the system you have

Email: Chick


Freedoms just another word for nothing left to lose

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