Clog in A/C System?

[NickP]

I've just gotten around to getting the A/C working on my s50 swap.

I've put in a new receiver drier and had hoses fabricated to mate up to the s50 compressor.

Yesterday I started filling it with a can of r134a on the low pressure hose and it took in about 12 ounces and started cooling nicely. The PSI was around 32. After a few minutes I noticed it stopped cooling so I shut down the car. The PSI was showing vacuum and then over 15 seconds moved back to 32 PSI. This morning the PSI was still showing 32 PSI (at least I have no major leaks) but as soon as I turn on the compressor it reads vacuum again.

I assume this is an indication of a clog? I am assuming its probably in the expansion valve. Can I test by disconnecting hoses and seeing which section holds vacuum? Any other recommendations?

[Toms73NovaSS]

When I went through my system I took it all apart and sure enough there was a few flakes of rust plugging up my expansion valve! It is the smallest diameter part of the system and most likely to plug.

[NickP]

I ordered one yesterday :-) Grand Island must be busy with the amusement park before labor day.

[Eric Giles]

From talking with techs that have worked on E30 a/c systems over the years, the expansion valve is generally the culprit of leaks and other issues. I always replace it along with the receiver/dryer and associated o-rings whenever I am working on the a/c.

[bimmer630]

I have an E30 that some other shop did a conversion on, replaced the condenser, compressor, evap, and exp. valve. They brought it to me because there was an "electrical issue" they couldnt figure out. I found a loose connection at the original low pressure switch (It has the original drier on it for some reason).
Once I fixed that, the compressor would activate. I charged the system with 1.5 lbs, after sucking down a vacuum for a LONG time, and the system struggled to take a charge. Once it did, the high side was between 250-300, with the low side lower than normal, in the 20psi range. vent temp warm

I took some stuff apart and found the inlet to the compressor has a cone shaped screen and it was clogged. When I pulled the fitting off the compressor, a small metal ball, a BB, or maybe a clump of metal from the orignal (blown) compressor. the piece went flying and I lost it.
anyway I thought I had it fixed after cleaning out the clogged screen.. Nope.. it still does the same thing.
I have a new exp valve here, but I dont want to waste it if its not the issue. I took the old exp valve apart and its not clogged, I also put a valve in there from a scrapped E30 heater box I have. Still the same symptoms.

What else can get clogged in these systems? I blew air through most of the lines and evap/condenser and there is flow, Of course I dont know how much flow, but they dont feel restricted. Also, Can a drier cause these issues? The only thing I can see going wrong with the drier is the dessicant gets too filled with moisture, or theres leftover mineral oil in it.. but I can blow air through the drier just fine too.
My next move is probably putting a drier in, because it should have been done by now anyway, but Im thinking that its not going to cure my pressure issue anyway.

the fill spec for r12 is 2.16 lbs on this system, Ive tried 2 lbs of 134, 1.5 lbs, 1 lb, etc.. and each fill level gives the same pressure results basically. (too high on high side). I have good flow across the (new) condenser