Report on 200Q R134a conversion

[Peter Golledge]

Listers,

I will add my tale to the many AC stories out there.. hopefully this
will
help some of you.  The result is very good thus far ~38F at the vents
and
mucho better cooling at idle than before.  I went to town and tore
everything
apart, some of you may wish to cut corners....

The car in question:  89 200Q (early model with single knock.. not that
it matters).

The problem that started all:  High pressure hose (compressor to
muffler) leaking badly.

The parts I used:

O-Ring/Port/Oil kit from NAPA
New receiver/drier from TPC
New Orifice tube from ACsource.com
AC hoses fabricated by local hose shop (Drivetrain Industries in
Denver... very good)
3 x R134a in 330gm bottles from NAPA
Additional R134a oil from NAPA (Audi TSB calls for 300cc for a complete
flush/fill)

The tools I used:

Lots of large spanners (need 17/19/22, 11/8" and probably a couple of
others I can't
remember... sears does a box of big ring/open spanners which works very
well)

R134a manifold set from local tools place.

R134a bottle tape from NAPA

An old refrigerator compressor (vacuum pump... works well pulls ~25mmHg
but very slow)

The procedure I used (new O-ring for each fitting is assumed...):

1.  Remove AC compressor (keep orings for matching with new ones from
kit!)

2.  Remove hoses, take to decent hose shop to get new ones fabricated or
pay mega $$$
    to Audi.

3.  Remove old receiver, remove Orifice tube from from line next to
receiver (fittings
    are 19mm/22mm from memory).  If the Orifice tube has lots of metal
fragments
    prepare to rebuild or send off your compressor.

4.  Disconnect condenser (may need to remove fender liner to get to
fitting)

5.  Disconnect pressure switches on pipe in front of condenser

6.  Remove condensor/muffler assembly

7.  Run a solvent through the condensor/muffler/evaporator/hardlines.  I
used Mineral
    spirits and blew everything dry with shop air, there are specialized
solvents but
    I was happy to let things evaporate.

8.  Remove manifold from compressor (don't damage the big seal on the
manifold, this appears
    to be unobtainium and must be reused!).

9.  Remove as much oil as you can by spinning the compressor with the
ports pointed downward.
    Don't run solvent through the compressor!

10. Reassemble manifold using new O-rings torque to specs per Bentley.
Add 80CC of
    PAG oil to compressor.

11. Remove schrader valve from manifold and install low side (blue)
R134a port.

12. Reinstall hoses.  Getting the low pressure hose into the hole under
the blower
    unit is very difficult.  I put it through the drain hole and padded
it to avoid
    chafing.  I added 20cc of PAG oil to each hose (measure to ensure
total is 300CC!)

13. Install condensor/muffler, re-attache hard line, high pressure hose
and pressure switches.
    I added 50cc of PAG oil to the condenser)  Remove schrader valve and
install high side
    R134a port onto pipe on condenser.

14. Install Compressor, attach low pressure/high pressure lines and the
clutch coil wire.

15. Clean/dry/install old orifice tube (I used a new one #AS440475V from
acsource.com)

16. Add balance (150cc) of oil to the receiver.

17. Install receiver (will be a PITA you may want to install low
pressure hose before mounting
    this item onto the bracket).

18. System should now be sealed, hook up manifold gauges and vacuum,
evacuate and confirm
    that the vacuum holds with the pump disconnected.  Put system under
vacuum for a number
    of hours (the longer the better) to evaporate and moisture/solvents
in the system and
    remove any air.

19. Remove vacuum pump, again verify that vacuum holds.

20. Jumper low pressure switch (next to receiver) and start the car with
AC system on max low.

21. Attach tap to first R134a bottle, attach to manifold.   Open low
side manifold valve
    (ensure high side is closed!).

22. Hold Bottle UPRIGHT... don't want to inject liquid R134a now do we!

23. Use tap to puncture and slowly let R134a into the system.   You
should see high side
    pressure start to build, low side will cycle between 0 and 50/60
depending on compressor
    cycling.

24. Once first bottle is empty (may need to submerge in warm water to
keep things going)
    repeat step 23 with second bottle.  Look for excessive high side
readings (300+) my
    old Orifice tube was clogged and I got excessive high side with very
low low side (0).
    I had to remove refrigerant and replace the orifice tube.

25. Audi TSB indicates that R134a charge is 900gm so you can just shove
the whole third
    bottle in!  I kept filling until low side was a consistent 30-35 and
vent temps were
    < 40F.

26. Remove jumper from low side switch, the compressor should cycle from
time to time.

Cheers
--
Peter Golledge