Air Conditioning Lesson's Learned

["miltdanfoss" <dan.foss@xxxx>]

In the Space business, after a launch we hold what we call 
a "Lesson's Learned Meeting," so everyone can apply our lesson's 
learned to future launches, which helps make things flow smoother in 
the future.

I want to share my A/C refit lesson's, for those needing or 
considering tackling it in the future.

I took my car in for a estimate to charge the A/C, and found that 
having the compressor out of car for 8 months, had caused it to begin 
to freeze up - when turning the compressor clutch (center nut, common 
to pulley), with a socket/ratchet - it turned, but was obviously 
bound. If the prior owner, who is the one who removed it, had stored 
it with oil and closed the rear ports, it may have made it to being 
reinstalled. I could have rebuilt it, but opted for a new unit.

My estimate to have the compressor repaired, system updated and 
converted to R134A was $910. Being cash poor due to buying a 
DeLorean, I decided to try the conversion myself.

First thing I downloaded the two guides on the DMCNEWS tech site. 
Thank you!

I bought a new compressor, drained the mineral oil (per Dave's 
section on the DMCNEWS tech site), bought a new accumulator (actually 
two - DMC-H couldn't tell me what desiccant was inside theirs, so I 
opted to return it and get one that wasn't a mystery), a refill kit, 
gauge and a GM orifice tube.

I took out the accumulator and since the system had already been 
converted to R134A before I bought it I wasn't so concerned with 
flushing it, so I just blew out the lines with oil free compressed 
air. 

The low side was easy to blow out and a lot of ester oil came out. 

The high side was blocked, so I disassembled the other line to the 
evaporator (it goes through the fire wall). It is the line that is in-
between the accumulator and the right wheel. 

This is important because I couldn't find anywhere else that told me 
where I could find the "white GM Orifice Tube" to replace. It is in 
this line. It actually was what was blocked. It is the system filter 
(according to the back of the new orifice tube package). It took me 
an hour nibbling away at it with a pair of long nose pliers until I 
could get the brass tubule out. After that I ground down one of my 
wife's crocheting hooks (with permission), to the right size to fit 
in the tubule hole, then I extracted it. Of course I also used a pipe 
cleaner first (the kind for copper water pipe), and then blew in 
compressed air the back way to keep from getting contaminants in the 
system.

Finally, I reassembled, and vacuumed down the system and left it over 
night. I then checked to see if it held the vacuum by depressing the 
needle at the low side port. It held and so I reapplied vacuum for a 
half hour and then charged the system. 

Yes I did use the cans WITH oil, (call me the rebel) of course I made 
sure all the oil was out of the system first, and put in two cans 
before I started the car, to make sure I had enough oil in the new 
compressor. 

It now blows ice cold. All pressures are within specs and I used the 
amounts in the workshop manual, compensated for R134A (5% less).

Morale of the story - replace the orifice tube every time!!

Dan in Cocoa, FL (3932)