Automotive Air Conditioning Information Forum

I would like to thank the heavy hitters on here, and Tim, for a super knowledgeable site!

I have many years of experience with mobile, residential, and low temp commercial (freezer boxes to -40°). My full time job is with my nephew restoring vintage vehicles, and not stuff like a tri-5 chevy. Earlier, where you have to fab up your own system (1931, 1947, etc). Every car that we do is retrofitted with AC, after all, this is Texas.

Mobile is by far the most challenging.

I thought I knew a lot about mobile, but have had a few stumpers, which this site straightened out for me.
Such as weak electric fan on condenser, re-heating, attrition, etc, things that are obvious once you are aware of them.
I have read all threads back through 2016 and the knowledge is amazing.

We weigh in refrigerant with a made-for-purpose electronic scale, always use a micron gauge where we shoot for 1000-1200 microns (can never seem to get below that, even on residential). We typically do a triple evac.

Those posters that vac for 30 min amaze me that it ever works, and it is also amazing how much resistance there is to follow the advice of the pros.

Thanks again, pros!!!!
Dave

Dave, You can get below 1200 microns on residential very easy. I'll bet you are using a manifold and not the black vacuum rated hoses. They make a difference. Also, the compressor oil holds moisture. I regularly get below 500 to 400 microns. The reason why you may not get below 1200 on MVAC is again the above reasons and the compressor seals just do not yield as tight a system as desired.

Doug, I am not familiar with the black hoses.
Do these entirely replace the traditional red-blue-yellow setup? Or are they used for vacuum only.

I can easily get 300 microns on my tree with the red and blue joined together with a special quick connect union I made (we always test the tree before we start a job), but once I connect them to the system I seldom get below 1200. One time I got 1030.
We vacuum for at least an hr often 2 hrs. I have seen the vacuum drop quite a bit in the second hour.

And we do not like to leave a system in vacuum overnight.

Black hoses are for vacuum and charging. They do not allow for off gassing. They are made by yellow jacket, CPS, and Appion. Glad to see you're using a tree and not a manifold. Also try using a small amount of Nylog at the connections, and remove the schraders . Use core removers. You may want to see vacuum set ups on you tube.

Done. Ordered. Not what you see hanging on the walls at Johnstone and Baker.

I'm on a couple of HVAC forums and have seen how they set up their trees. Never a word about black hoses, tho.

Thanks!

Do an internet search "Best vacuum Practices by Jim Bergman"