A/C 200q 20v

[TooManyAudis at aol.com]

Hi tom,
I am looking at the same repairs to bring my 200 in to the R134 era.  Can 
you tell me what you did to your system and how much it costs.  I am looking 
at $450 to repalce dryer and recharge system with no guarantee of no leaks 
later.  They claim that they need to rechrge the sytem, them do the dye test 
for leaks.  Any insight appreciated.
Mike

Mike,

I usually follow the approach that I would rather do the repairs myself, 
unless it is something that I absolutely don't want to touch.

Items needed:

Receiver Drier -- $35 to $40 Autozone had one that worked.
Vacuum pump - $125 off Ebay or pawn shop
Manifold and guages -- $50 off ebay or pawn shop
Low Side and High Side Fittings -- $15
Oil and R-134A -- $25
Filling hose and connector -- $10

Before I replace anything, I usually vacuum out the system and test if it 
holds a vacuum.  This will tell you if you need to track down leaks.  Leaks are 
most common at the compressor, switches and joints betweens hoses.  If it is 
oily and dirty, you've got a leak.  You may be able to simply tighten the joint 
or switch, but you will most likely have to replace a seal.

The receiver/drier is located under the plastic shield between the firewall 
and the windshield.  You need to remove a wiper to get the plastic tray off.

Removing the Receiver/Drier requires a couple of large wrenches or vice 
grips.  The tricky part comes with the clamp that holds the unit down -- you need a 
1/4 inch socket wrench and it is a tight fit.  I had to be creative and do 
some manuevering, but it was manageable.

Look in your Bentley to see if you need to get the orifice tube out and clean 
it.  I didn't do this, but I wish I had, just to eliminate it as a possible 
problem area.

Place the receiver/drier back on, then use new 134-A fittings over your 
existing service ports.  Low side is attached to the compressor.  High side is 
beside the condensor.

Vacuum for at least an hour.  I then leave the guages attached and walk away 
for an hour or so (overnight if possible).  If there are any leaks, they will 
show up by then.  This isn't to say that just because your system holds vacuum 
that you are all set.  there's a big difference between -29 lbs and 250 lbs 
(or more) of pressure.)

At this point, a pro shop should flush the system of any R-12 residue and 
oil.  I've never taken this step, and have had systems working for 4 and 5 years 
later, so to me, it's optional.  Then again I am having a few problems now, 
but I think it's unrelated to this step.

If you have no leaks, fill with oil, then with as much 134-A as the system 
can take.  Then, jump the low pressure switch (right by the receiver drier), 
turn the car and fill system until it get up to 30 lbs or so on the low side, 
then check to see if your temps out of the vent are acceptable.  More refrigerant 
doesn't always mean better cooling.  Make sure your high side isn't too high 
at this point.  You basically want the least amount of refrigerant to make the 
system run properly.  There should be a chart in the Bentley telling you the 
proper vent temps and pressures at given outside temps. 

A good estimate for R-134-A is to use 80% of the amount listed on the car for 
R-12.

The other alternative is to use Freeze 12 instead of R-12.  I did this with a 
van at work, and there had no problems.  The advantage is that you don't have 
to flush the system or change oil with Freeze 12.  Some people just top off 
with the Freeze 12 with the remainder of the R-12 left from when it was a 
working system.  I don't know if I would do that or not.  Others on the list 
probably have more experience in these things than I do.

That's a down and dirty overview, and certainly not the only one you'll get.  

Let me know if I can help.

-- Tom