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Need some help and advice???

TnTahoe on Thu July 29, 2010 10:46 AM User is offline

Year: 2003
Make: Chevrolet
Model: Tahoe
Engine Size: 5.3L
Refrigerant Type: 134a
Country of Origin: United States

Ok first off my truck has rear air. My a/c worked fine but it made a terrible noise. Read something about oil causing the noise so I decided to get a new compressor. Well when I replaced the orifice tube it had some metal shavings in it but not a large amount. So I took that as normal wear and tear but i used compressed air to blow out the condenser and tubes and installed a new compressor and drier and I added pag oil to the compressor, drier and condenser. I had a vacuumed pulled on the system but when it came time to charge the system, the high side was 200ish but the low side would stay within the 60-70ish range and would not go any lower. So the mechanic told me it was the compressor so I sent it back and got another compressor and drier and I also bought a new condenser. When I removed the orifice tube it had more trash in it than the original one so what could have caused this? This time I plan on doing all of the work myself. My truck calls for 8oz of oil and I was wondering should I just divide this among the 3 components? And also some of my original o-rings had like a metal washer around them, can I use regular o-rings to replace them or do i need the ones with the metal surrond? And also my truck idles lower than 1000rpm, so should I raise the idle to 1500 rpm? Also since my idle is so low would that cause my gauge readings to be incorrect?

Dave in Texas on Thu July 29, 2010 11:43 AM User is offlineView users profile

Compressed air doesn't do the flushing job. A solvent is needed to clean everything out properly. Read the sticky about flushing out the system. Look in Forum Catagories for that. I'd go 60-40 with the oil between the suction port on the compressor and the accumulator. Not sure about the metal-surround on the washers. Maybe someone can answer. Nylog would help sealing all connections. Higher idle would be needed when charging the system.

At 2, I went home with a 10. At 10 I woke up with a 2 !!

Edited: Thu July 29, 2010 at 11:45 AM by Dave in Texas

HECAT on Thu July 29, 2010 12:06 PM User is offline

The only thing blowing a condenser does is verify it is nor hard blocked. There are so many paths that the air will just blow over and around the debris and oils.

1 or 2 specs of metal in the orifice tube screen is concerning but can be considered normal wear and tear. Some metal shavings in combination with a noisy compressor is a red flag.

New compressor, filter, and 8 oz (?) of fresh oil. What about the oil that was already in there? If the system had previously got low on charge (can still cool), and lubrication return to the compressor had slowed enough to cause the compressor to fail (GM tech states 65% do); then all the original oils were still in the dual evap circuits. Oil overcharge can cause higher than normal low side pressures.

More trash now in the OT, this is the red flag now waving hard in your face. It is caused by either not removing the debris from the first compressor, or it is debris from the second compressor; the failure is the cause, now it has to be cleaned.

Hanging another compressor and adding another full load (8 oz) of oil will not be the answer. There is link in my signature that explains a lot more about flushing, and what it takes to clean up something like this.

Use the type of seal that has been working, don't add another problem to deal with.

Set idle according to factory spec. Tests at 1500 RPM are to simulate cruising (driving down main street).


HECAT: You support the Forum when you consider for your a/c parts.


TnTahoe on Thu July 29, 2010 12:12 PM User is offline

Well I now have another compressor, orifice tube, condenser and drier. I also noticed that when I removed the replacement compressor that no oil came out of it, and when I returned it to the vendor he said that the compressor had burned up, I put 2.5oz of oil in it before I installed it, is there a certain hole to put the oil in?

HVargas on Thu July 29, 2010 12:25 PM User is offlineView users profile

You can put the oil directly into the suction port of the compressor. However, if there was debris in the system, which you verified, then no matter how much oil you put in the compressor, it was destined to fail again. You are on the right track with getting a replacement compressor, accumulator, orifice tube and condenser. You are also going to want to replace the rear expansion valve as well. It is part of the system and is exposed to the same oil and debris as the main front components. If you are going to do it yourself, I would highly recommend taking the vehicle to a shop once you have the lines unhooked and accumulator removed and orifice tube and rear expansion valve and having them flush both front and rear evaporators and all of the lines in the system to ensure there is no oil or debris left in the system and essentially start over new. Failing to do any of these steps almost certainly will affect your cooling and the life of the new components. As far as the compressor goes, since they do not have a sump for oil to sit in, rarely do they have more than an ounce of so of oil in the compressor on your vehicle. The oil is designed to travel through the system with the refrigerant.


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TnTahoe on Thu July 29, 2010 12:40 PM User is offline

I was under the impression that my vehicle did not have a rear expansion valve or evaporator. My rear ac controls do not engage the compressor if the front ac is not on. So you can only add oil to the suction side of the compressor, im assuming that I added the oil to the wrong side, and also my replacement drier had alot of oil in it. And also do I need to add any oil to my new condenser and drier?

iceman2555 on Thu July 29, 2010 3:56 PM User is offlineView users profile

If your vehicle is equipped with rear AC...then it has a TXV and evaporator. The fact that the rear unit does not engage the compressor is irrelevant. The rear unit performs as a supplementary cooling system for the front unit.
The question concerning lubrication is most important. This system requires 11 oz of PAG 46. This vehicle is equipped with a Denso compressor and the lube spec if different from the H series compressor. 2-3 oz of lubricant is sufficient for the compressor. 4-5 should be added to the accumulator. The remainder should be added to the liquid line that feeds the rear unit. The system will perform lubrication distribution. The key to proper lubrication is not only the correct lube charge, but the correct charge level for refrigerant. Not only the amount of refrigerant but the ability of the system to flow lubricant will have an effect on compressor longevity. That means no restrictions...none...nada...not in possibly the condenser.
The issue with pressures is common with this type system...esp when the condenser is restricted. The temp/pressure drop across a restricted condenser is sufficient to result in a perceived high side pressure that is 'normal' (?). The encountered elevated low side can be contributed to a reduction of refrigerant flow and the location of the low side port that is exposed to a tremendous amount of engine heat.
Contamination in the orifice tube should have been a major clue to replace the condenser. Resultant debris from a failed compressor will severely contaminate the inlet side of the condenser. A reduction of flow orifices within late model condensers has resulted in the condenser becoming the primary filter for the system. Once this material is in the condenser it is not going to be removed with a 'standard blow thru' flush procedure. Flushing a late model system requires specific flush equipment to accomplish this necessary part of the repair. The statement that air moved thru the condenser simply informs me that at least one tube is flowing....this is not a valid test for condenser performance. The extra debris that was evident after the primary failure is probably residual debris from the previous compressor failure that was not removed during the flush procedure. Can not state it enough the system must be clean...totally. This is not a step to skip or perform 'half-assed'.
It is necessary that this system be cleaned.....completely....or simply purchase two compressors when you go to the local jobber.....they will be needed. Wonder is the returned compressor was returned as being 'defective'? The compressor was not was pumping it's heart failed due to the lack of an installer to properly prepare the system.
This compressor requires specific 'sealing washers'. Check with site sponsor...or local GM dealer for the correct sealing washers. Standard GM washers will work at times...but leave excessive tolerances that may result in future leakage.....interpret this as another compressor replacement....and more unnecessary expense. Do it right the first time !
Once the components are installed....suggest to have the system professional evacuated and recharged. This system should be recharged utilizing a method of measuring the exact amount of refrigerant added to the system. Pressures are not an indication of a properly charged system.

The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

TnTahoe on Thu July 29, 2010 4:25 PM User is offline

Im pretty capable of doing the work myself, and i thank you for all the advice, i was just getting some things clear before i do it, how exactly would i get the oil to the rear through the liquid line that goes to the rear? And do I not add oil to the condenser? What rpm should I charge the system at also? Why does it say 11oz of oil when everyone that I talk to says 8oz even the parts store?

70monte on Thu July 29, 2010 5:53 PM User is offline

To verify whether or not you have rear air, look for lines that go from the engine compartment and go under the truck toward the back, probably on the passenger side. Look under the rocker panels on the passenger side to see if you have AC and heater hoses going back there. If you do, you have rear air. If not, you don't. Do you have any information on a sticker that is on top of the accumulater? If so, what capacity of oil does it say. If it says 8oz, you only have front air. 11oz means dual air.


TnTahoe on Thu July 29, 2010 6:15 PM User is offline

Im 100% sure that I have rear air, the rear air stuff is located in the rear passenger side of the cargo area

Chick on Fri July 30, 2010 11:01 PM User is offlineView users profile

Front only add 8 ounces, with rear air 11 ounces, the parts guys don't fix cars, they sell parts...

Email: Chick


Freedoms just another word for nothing left to lose

TnTahoe on Sat July 31, 2010 7:34 PM User is offline

O so how much should i add to the compressor, condenser, and drier

iceman2555 on Sat July 31, 2010 8:36 PM User is offlineView users profile

This was covered in a previous post. It is not necessary to add lubricant to all parts of the system. Simply add 2-3 oz to the suction side of the compressor. 5-6 into the inlet side of the accumulator. Add the remaining 3 oz to the liquid (small) line that connects to the rear unit. The system will balance itself. The two major locations for lubricant within the AC system are the compressor and accumulator.
The absolute key to a successful AC repair is the recharge. Charging with cans and attempting to utilize pressures is a good path to an undercharged system and the result will be the loss of your new compressor and a re contamination of the system. A suggestion to have the system evacuated and recharged by a professional who is able to utilize the correct equipment is offered.

Good luck!

The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

TnTahoe on Mon August 02, 2010 8:57 AM User is offline

I have access to properly evac the system, and I will be using a 30lb container of refrigerant to recharge with manifold gauges. Charge as a liquid or gas?

TnTahoe on Thu August 05, 2010 9:44 PM User is offline

Charge as a liquid or gas?? And I also heard that you can clean the lines out with brake cleaner??

fasto on Thu August 05, 2010 10:29 PM User is offline

Charge as a liquid through the high side until either you weigh in the full system charge or put in as much refrigerant as you can. Then, close the high side valve and leave it closed. Turn the 30lb cylinder upright, rotate the compressor by hand a dozen turns, and start it up. Charge refrigerant as a gas into the low side to reach the required weight in the system.

TnTahoe on Mon August 09, 2010 12:37 AM User is offline

is there a special tool or something for an orifice tube, it seems that i have an orifice from hell, ive broken 3 orifice tubes trying to get them back in the tube, and its like an act from god to remove the left over pieces, ive had to drill 2 of them out, so is there some special way to do this or what

iceman2555 on Mon August 09, 2010 1:48 AM User is offlineView users profile

Just a point of information. How many compressors have been installed on this it two or three?
Have you attempted to lubricant the orifice tube prior to installation? A bit of lube goes a long way to ease this process.
The site sponsor sells a very good and highly informational book on AC service. Suggest that this might be a very good starting point to repair this system. It is quite obvious from the post that additional information is needed.

The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

TnTahoe on Mon August 09, 2010 7:22 AM User is offline

This is the second compressor and yes i did lube the orifice tube prior to installation it just seems that something is stopping it from seating right, and the reason that i ask the questions is to make sure that Im doing things right

TnTahoe on Tue August 10, 2010 3:18 PM User is offline

So its ok to add liquid r-134a to the high side with the engine off?

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