99 Tahoe - AC Problem

[jwh]

I have a high-mileage 99 chevy Tahoe and I've determined (mostly due to
loud clanking noises) that the A/C compressor has failed and needs to
be replaced.

Ok, so I've removed the compressor as well as the accumulator, the
front orifice tube, and the rear A/C unit expansion valve. I didn't
see any debris in any of these places so I'm going to keep the existing
condenser, evaporator, and tubing. This is an R134a system and the
warning label on the accumulator says to be sure to add proper
lubricant (i.e. PAG).

My service manual says:

"Determine the amount of oil remaining in the accumulator and add that
amount."

In another place it says:

"Determine the amount of oil remaining in the compressor and add that
amount."

Hmmm, confusing...

The problem is that there is no oil, at least none that I can find, in
the accumulator or in the compressor. I do find "trace" amounts in
that if I stick my finger in the accumulator there is a film of oil
there as is to be expected.

So my question is HOW MUCH oil is to be added to this system prior to
recharging with R134a? And where should it be added? One place in the
service manual says add it to the compressor, another place says add it
to the accumulator. Also, WHEN should it be added? Prior to
evacuating the system or after evacuating but prior to adding the
R134a?

I don't want to trash my new compressor before it even gets going...

Thanks, and any other tips on this particular system would be
appreciated. BTW, this is the 4x4 4-door Tahoe w/ 5.7L V8. Has the
rear A/C option as well.

[aarcuda69062]

In article
<1155559384.0...@i3g2000cwc.googlegroups.com>,
"jwh" <jwh...@gmail.com> wrote:

The oil circulates with the refrigerant when the system is
operating. When the system is shut down, the oil settles in each
of the components where it remains until the system is operated
again. Each component has its own oil capacity.
The only certain way to assure the correct oil capacity is to
flush everything and start from scratch. The accumulator is not
to be flushed, nor is the compressor, and since you are replacing
these items, all you need to do is add the specified amount of
oil to them before you install them (install the accumulator
last). That leaves the front evaporator, the rear evaporator and
the condenser. Each will have a recommended oil capacity, that
capacity may be listed in the service manual under the
specifications or it may be listed under the remove and replace
instructions for those components.
Oil is added at the time that the component is installed or
re-connected back to the system.
You will need new O-rings for each component that you disconnect
when you flush. Do NOT lube the O-rings with PAG oil, use
mineral (R-12 oil), PAG oil absorbs moisture and will cause the
fittings to corrode.
In order to prevent pulling your new fresh oil from the system
when evacuating, you'll need to pull your vacuum from both the
low side and the high side at the same time.