Automotive Air Conditioning Information Forum (Archives)

meamjw on Sat July 26, 2014 3:41 PM

Year: 1994
Make: Dodge
Model: Dakota
Engine Size: 3.9
Refrigerant Type: 134a
Ambient Temp: NA
Pressure Low: NA
Pressure High: NA
Country of Origin: United States

AC was still cooling but not up to par. Removed orifice tube and the screen was totally covered with very black oily looking stuff. Put gasoline in container and swished tube in it, stuff did not wash off. Sprayed Gum Out carb cleaner on it and that did wash it off. I don't know how unit was still cooling at all. And I have no idea what the stuff is nor how it got in my AC
Now I think I surely need to flush the entire system. Have never heard of anyone flushing AC with carb cleaner but don't think any conventional cleaners will get rid of this crap.
If I blow carb cleaner through system I'm guessing I will need to remove both lines from compressor then splice them together in some temporary form to get the cleaner to flow all the way through the system. Then I figure I can blow compressed air through it for about 30 minutes to get all the carb cleaner out. If there are any true AC experts on this forum, please tell me if this will work. Also tell me what this stuff may be and how it may have got into my system. Then one more question: Is there likely enough of this crap in my compressor to cause a problem?

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Jay Wells

HECAT on Sun July 27, 2014 1:12 PM

Gasoline did not cut it, just like mineral sprits would not. It is not a mineral based deposit. The carb cleaner is going to contain solvents that will be effective on the synthetic (PAG or POE) oil residues. However, the carb cleaner will also contain chemicals that can react and damage hoses and seals, it may also establish oxidation (corrosion) on certain metals; for this reason, it is definitely not what I would recommend to use as an A/C system flush.

Your thought process is on the right track but A/C flushing is much more complex than a solvent rinse. In addition to understanding the solvent chemistry (an example of which you have already posted); the right solvent has to be delivered with volume and velocity for it to be able to cut the residue, penetrate all the parallel paths, and bring out all the crap. Your current plan is a recipe for disaster; the end result will be the addition of carb cleaner to your already contaminated system and not much more.

We do not flush a systems from the compressor ports as this just pushes carp from one part of the circuit into another. The orifice and filter should also be removed and with the line sets included (they need to be cleaned also), and they are used to perform 2 separate flush and dry out processes. That is the condenser circuit (back flushed) and the evaporator circuit (forward flushed) separately.

Yes, your compressor is contaminated also. There is a compressor flush/rinse (no solvents) procedure in the "procedures page" if you want to attempt to reuse; I would replace.

What is it and how did it get there? If no one has ever touched this system (unlikely with a 94 model), it is carbonized oil from compressor overheat. This most often happens when the system has been running low on charge. More often it is some sort of system additives that we affectionately call "snake oil". ICE32 will do this as it does not mix well with the liquid refrigerant as the PAG or POE oils do; therefore it can be filtered out at the screen. It can also be the result of poor flushing at last repair. Who knows?

Please read the paper in my signature for a further understanding of A/C flushing.

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meamjw on Sun July 27, 2014 7:11 PM

Thanks a lot HECAT. Your reply was helpful and the PDF was extremely helpful.

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Jay Wells

HECAT on Sun July 27, 2014 8:34 PM

Glad you found something helpful. I just read my post again; and nearly choked laughing so hard. We are not trying to remove fish (carp), it is the crap we want to get out.

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Jag987 on Wed July 30, 2014 11:45 PM

Maybe you don't mind the carp in the system, but I would want to get it out....after I figured out how it got in.

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I bought a can of 134a at w**-mart that had a stop leak, oil, and dye in it. It also had a hose and a gauge, so now I'm an AC pro!

HECAT on Thu July 31, 2014 1:21 PM

Yup, something would smell very fishy. I wonder what the boiling point of Carp is? How it got in would truly be a story to hear, but after it had been in there for a short while, it would all just be the stinkin' crap that needs to be removed.

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