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Out gassing ?

slcbird92 on Tue May 08, 2012 6:22 PM User is offline

Year: 1993
Make: Winnebago
Model: Diesel Pusher
Engine Size: 5.9
Refrigerant Type: 134a
Ambient Temp: 95
Country of Origin: United States

Hello All, I have recently replaced the dryer, expansion valve and compressor on this 1993 RV coach. I am in the process of performing a 134a conversion. After thoroughly flushing the roughly 60 foot of barrier line, the evap, and condenser I purged with compressed air .I then did a rough leak test by pumping down the loop for 30 min. (i have a 2.5 CFM vacuum pump) and checked the vacuum . The needle did not budge from -30 Hg. I then pumped down for another 2 hrs and noticed a solvent odor when the pump first started up. Not surprising with the volume in this system. After letting the system sit overnight I still had vacuum but only in the range of -10 to 15 Hg. next I pumped down for about 6-8 hours and after 2 days I'm at -25 Hg. So my question is should I or keep pumping down or call it good and charge? My concern is remaining solvent in the system.

GM Tech on Tue May 08, 2012 7:27 PM User is offline

Sounds like you still have flush left in the system--this is why I have never flushed with anything other than refrigerant- You should NEVER put anything into a system you can't get out and is foreign to the system- especially a solvent that dissolves oil and dries compressors. I can'y tell you how many warranty service compressors used to come back- wanting paid for "bad" compressor that were full of flushing solvent- smelled like turpentine when you uncapped them and opened them up with the seized washed out internals.

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......

slcbird92 on Tue May 08, 2012 7:47 PM User is offline

That's what I was thinking too, but from my experience in the vacuum field that solvents out gas under a vacuum and although it takes time will pump out as a vapor. Of course I was working with much larger pumps in that career. I did use the Hecat flush so I felt I was using a good product that would evaporate given enough purging and time under vacuum?

Cussboy on Tue May 08, 2012 11:08 PM User is offline

You should be able to get more vacuum than 25.

HECAT on Wed May 09, 2012 7:16 AM User is offline

I would open it up and purge more with lots of dry forced air (or nitrogen). The HECAT solvent is designed to remain liquid for flushing with common air driven delivery methods and requires follow up with a high flow of forced air to remove and evaporate down to trace levels. Given the size of this system and the length of lines; there may be many places for solvent to pool and this may require considerable effort. Smelling the solvent as GM tech says, and as you have noted in the vacuum pump discharge; is a sure sign too much solvent is still remaining in the system and the pump oil is now contaminated. Vacuum will evaporate the remaining components of the solvent trace, and this can be verified with the use of a micron gauge. However, the common MVAC vacuum pump should not be used to try and remove any substantial liquid volume of solvent.


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


Edited: Wed May 09, 2012 at 7:21 AM by HECAT

slcbird92 on Wed May 09, 2012 2:09 PM User is offline

Thanks to all for the replies, I'll get back to purging tonight!

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