88-94 5.7 Suburban A/C Diagnosis and Tuning

L31MaxExpress

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FWIW...
Known composition of counterfeit R134a refrigerant:
•60 % R22 (+ R30, R142b – traces)
•40 % R40 – methyl chloride
Compounds such as R-40, R-22, R-142b, R-152a, and R-12 have been found mixed with R-134a in
newly filled refrigerant cylinders marked as containing R-134a. There have also been instances of
counterfeited brand name R-134a cylinders sold containing refrigerants other than R-134a.

Methyl chloride is corrosive to aluminum.
 

1998_K1500_Sub

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FWIW...
Known composition of counterfeit R134a refrigerant:
•60 % R22 (+ R30, R142b – traces)
•40 % R40 – methyl chloride
Compounds such as R-40, R-22, R-142b, R-152a, and R-12 have been found mixed with R-134a in
newly filled refrigerant cylinders marked as containing R-134a. There have also been instances of
counterfeited brand name R-134a cylinders sold containing refrigerants other than R-134a.

Methyl chloride is corrosive to aluminum.

Presuambly one wants to know, at least:
- is the R134a component of the liquid greater than... 95%?
- are the contaminants, if any, corrosive / reactive in the system?

The first question is probably easier to answer than the second.

Is there a way to estimate the "percentage of contamination" easily in the field?

Or does one need a mass spectrometer or gas chromatograph ($$)?
 

L31MaxExpress

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Presuambly one wants to know, at least:
- is the R134a component of the liquid greater than... 95%?
- are the contaminants, if any, corrosive / reactive in the system?

The first question is probably easier to answer than the second.

Is there a way to estimate the "percentage of contamination" easily in the field?

Or does one need a mass spectrometer or gas chromatograph ($$)?
I have a friend that has a Robinair Identifier. Those range from $1,200-6,000+ depending on brand. I am sure some lab could do more in depth testing.

Doing a little more research, R22 seems to be a very common fake for R134a. R22 will also put out a small flame. That may also explain why I am looking at straight propane like pressures and low cooling. R22 works at a higher pressure than R134a.
 

Wildblue19

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Evacuated and recharged with falcon 152, with as much as I could get out of 4 cans. And for the results ...

Ambient 99°F, center vent 70°F at idle, 62°F highway. Recirc knocked down vent temp to about 58°F. General increase in delta by 5° across the board from what we saw with R-132.

This seems to correspond with the appx 10-20% efficiency increase shown in research papers on 152 use.

Is the interior more liveable 5° cooler than it was? Absolutely. Was the R134 used fraudulent? Possibly. Is there something still inherently wrong with the system? At this point, I just don't know. These are my pressures after the test ride at idle.

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L31MaxExpress

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Evacuated and recharged with falcon 152, with as much as I could get out of 4 cans. And for the results ...

Ambient 99°F, center vent 70°F at idle, 62°F highway. Recirc knocked down vent temp to about 58°F. General increase in delta by 5° across the board from what we saw with R-132.

This seems to correspond with the appx 10-20% efficiency increase shown in research papers on 152 use.

Is the interior more liveable 5° cooler than it was? Absolutely. Was the R134 used fraudulent? Possibly. Is there something still inherently wrong with the system? At this point, I just don't know. These are my pressures after the test ride at idle.

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I know you are probably fed up with the thing. Have you misted the condenser? Mist it a bit, then once it starts to dry out, mist again, and repeat for a few minutes. Curious where it equalizes out. See if you can drop the head pressure down under 250 and see where the low side ends up. If you can get down to the 250-275 psi range the low side reading should be down around 38-42 psi.
 

1998_K1500_Sub

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@Wildblue19, what the mfr of that temp probe you're using with the DVM?

Would you buy the same one again?

I don't have one, and that's just wrong.
 

L31MaxExpress

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@Wildblue19, what the mfr of that temp probe you're using with the DVM?

Would you buy the same one again?

I don't have one, and that's just wrong.
I picked this up a few weeks ago. Might just hook it to the van tomorrow evening when I am over at the shop for more data. So far I have used it on two houses and my shop ac to verify they were working correctly after servicing and to recharge a window unit. I have 1/4" SAE to 1/2" Acme fittings to hook it to R134a hoses. Its set up for something like 93 different refrigerants to calculate superheat and subcooling automatically. Not a high end unit but seems fairly accurate given its cost. Should be interesting to get some data pertaining to this experiment.

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L31MaxExpress

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Evacuated and recharged with falcon 152, with as much as I could get out of 4 cans. And for the results ...

Ambient 99°F, center vent 70°F at idle, 62°F highway. Recirc knocked down vent temp to about 58°F. General increase in delta by 5° across the board from what we saw with R-132.

This seems to correspond with the appx 10-20% efficiency increase shown in research papers on 152 use.

Is the interior more liveable 5° cooler than it was? Absolutely. Was the R134 used fraudulent? Possibly. Is there something still inherently wrong with the system? At this point, I just don't know. These are my pressures after the test ride at idle.

You must be registered for see images attach
Forgot to ask, did you hold at ~30 oz and then creep up to ~40? Or did you just cram ~40oz in there? I always charge my last anticipated can slowly a little at a time (2 second bursts), with equilization time between each 2 second burst. I also monitor the suction line temperature out of the evaporator. It is easy to go to far when the charge gets close to where it needs to be.
 

L31MaxExpress

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Just another thought. Yank the front blower motor, activate recirculation. See if the recirculate door is fully closing. 4° difference is less than I would expect given the ~20°F difference there is likely inside the truck vs outside of it. Hot outside air will drive the pressures up. Lacking an OBS truck at the moment that runs (8.1 from the Tahoe is on the stand) anybody know what the vent temp difference in their truck is between recirculate and outside air.
 
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