Adding Refrigerant without a Low Pressure fitting

Fred Munro munrof at
Sat Jul 5 17:57:43 PDT 2008

I believe the low pressure switch port contains a Schrader valve, so you
just unscrew the switch and screw on the adapter. You don't have to empty
the system.

I've attached the post from Tom Green, the chap who found the adapter.


I have broken the code on a/c charging through the low pressure

switch port. This has been a sore

point with lots of listers for a long time. So I decided that I

must "carry a message to Garcia".

I didn't have the problems Major Rowan encountered in carrying the

President's message to General

Garcia. It was as simple as reading Paul Waterloo's A8 posts on the

correct way and poor man's way to

recharge the a/c system. Please read both the posts, as they contain

essential information for recharging

the a/c system both by the correct factory method and the shortcut.

I am not here to encourage you to

recharge your system by either method. Unless you are confident in

your ability and knowledge, take it

to a professional. Otherwise, use at your own risk.

There are follow on posts that show where Paul Waterloo sourced his


I got mine at Midway Auto Supply. It is a FJC Air Conditioning

Products R134a Tank Adapter --Part# 6016.

I don't think a group buy can save over $2 unless there are a lot

more interested than I know of.


And, yes it works. It is a quick disconnect fitting, so if you are

using old screw-on fittings for your refrigerant

can or manifold, you will have to get adapters or a new hose set. I

encourage all to use a gage set, but otherwise

you are on your own.


  -----Original Message-----
  From: mboucher70 at [mailto:mboucher70 at]
  Sent: July 5, 2008 7:27 PM
  To: Kneale Brownson; Fred Munro; quattro at
  Subject: Adding Refrigerant without a Low Pressure fitting

  Kneale, I've got a good sense that mine doesn't have a low pressure
fitting.  Just to be certain, can you help me locate where it would be on
yours?  The "front of the return manifold on the compressor"...if I recall
the compressor is below the radiator, out of sight.  Would I be able to see
the black capped low pressure fitting on your 200q20vs from the same vantage
point that I could see the white capped high pressure fitting?  Or would I
need to be under the car to see it?

  Fred, in order to add the low pressure adapter to a car that doesn't have
one, I'm assuming that you'd need to first empty the system of existing

  I'm wondering if its possible to add refrigerant via the high pressure
fitting, with the car turned off.  I figured that the aerosol can is
probably pressurized enough to overcome the 60psi and get at least some
refrigerant in, but it surely won't overcome the 150psi present when the a/c
is on.  I appreciate that I'll get a lot smaller fraction of the can into
the car via the high pressure valve at 60psi than via the low pressure at
30-50.  The only impact of this is that I'll require more cans.  Anyone see
a flaw with this?

  ----- Original Message -----
  From: Kneale Brownson
  To: Fred Munro ; mboucher70 at ; quattro at
  Sent: Saturday, July 05, 2008 5:38 PM
  Subject: RE: How to Determine if your Audi is Actually Short of

  On my 200q20vs, there's a low pressure fitting on the front of the return
manifold on the compressor.  Black cap.  That's where I've put in

  Fred Munro <munrof at> wrote:
    You've connected to the high side adapter, as indicated by the lower
    pressure when the compressor cycles off.

    From what I recall Audi doesn't provide a traditional low side fill
    connection. I believe you can get an adapter that will fit on the low
    pressure switch port and use that as a low side fill, but it's a weird
    thread. One of the guys on the UrS list found a source of these adapters
    was supplying them to the list.


    Fred Munro
    '97 S6

    -----Original Message-----
    From: quattro-bounces at
    [mailto:quattro-bounces at]On Behalf Of mboucher70 at
    Sent: July 5, 2008 4:26 PM
    To: quattro at
    Subject: Re: How to Determine if your Audi is Actually Short of

    It turns out that Duracool is packaged with a gauge for measuring the
    refrigerant pressure, as well as high-side and low side adapters if you
    them. I picked up a package today and followed the instructions to
    the low side pressure. The gauge is color coded and indicates, the
    following ranges:

    0-25psi: low (green)
    25-45psi: filled (blue)
    45-65psi: alert (yellow)
    over 65: warning (red)

    I fitted the low side adapter, started the engine and turned the AC on,
    it run a few minutes, and atached the gauge. To my surprise, the
    read 155psi, dropping to 150 when the compressor cycled off. When the AC
    and the car were shut off, the pressure slowly dropped to about 70psi,
    never went below.

    Car is an Audi 100 1990. The adapter that I'm using is labelled as the
    pressure adapter. I'm connecting to the only visible 'filling' adapter,
    which is mounted in front of the AC/radiator, just behind the driver's
    headlight bulb.

    Car was bought 9 years ago, used. It is original R12 (no conversion). No
    refrigerant has been added since I bought it. Is it possible that
    over-filled it by a factor of 3 (150 vs 45) and its still functional?

    Any ideas?

    ----- Original Message -----
    Sent: Thursday, July 03, 2008 7:03 AM
    Subject: Re: How to Determine if your Audi is Actually Short of

    mboucher70 wrote:
    > Short of taking a car to an AC shop, what is a good method to
determine if
    > its actually short of refrigerant?

    I bought the gauges needed to test the AC from my local auto parts place
    (not a national consumer chain one, but one that services the local
    It cost about $100. You can get a cheaper one at Harbor Freight:

    Kent McLean
    '99 A4 Avant
    '91 200 Avant
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