Yeah, Patrick. Found this in my files from 6-97 GMC Motorhome News:
- ----------------------------------------------------------------------
Air-Conditioning Maintenance
After reading the "Refrigerant Change" item in the September '96 issue, I
purchased the three barrier-hose assemblies for my 1977 Birchaven. With
winter coming, I didn't think about doing the job until just recently.
When I removed the old hoses I decided to take the front off the
evaporator and heater-core housing because small pieces of greasy rubber
debris came out of the defroster opening this winter. Once inside, the
source of the rubber debris was obvious. It was deteriorated sealing rubber
that seals the doors in the system.
Noting that the expansion valve was corroded, I cannot help wondering
if just changing the hoses is enough. Should I bite the bullet and rebuild
the entire' air-conditioning system?
Rebuilding the entire air-conditioning system is a big bullet to bite,
Paul, but that will produce the best results. In Sandusky, we remove the
evaporator and heater-core housing through the grille opening and
completely remanufacture it. The doors are stripped and painted, and new
seals are installed along with a new expansion valve and a new thermostatic
switch.
Removing the evaporator and heater core housing is a job that most people
would like to avoid. A less effective but less labor intensive approach is
to only replace components that "see" pressurized refrigerant with the
exception of the condenser and the evaporator if they don't leak.
Maintenance Manual X-7525 cautions against removing the expansion
valve without removing the evaporator, which is very difficult to remove.
The expansion valve's sensing bulb is installed so its clamps cannot be
unscrewed from the front, but they can be cut with a pair of side cutters
because they are soft aluminum.
New expansion valves are somewhat different than original valves. They
are brass and are smaller in diameter. Attaching the sensing bulb with two
nylon tie straps snakes an almost impossible job easy, and the original
valve clamp can be reshaped to secure the valve to its mounting bracket on
the evaporator core. New barrier "O" rings should be used at every joint
that "sees" refrigerant pressure.
Old sealing material can be scraped off the doors that can be reached
and new sealing material can be applied to accessible door surfaces.
Partially resealed doors won't seal as good as new, but they will seal
better than they have sealed for a number of years!
The discharge pressure switch "sees" refrigerant pressure and a new switch
should be installed with a new barrier "O" ring. It is this "O" ring that
convinced me that everything that "sees" refrigerant pressure, including
the compressor, should be replaced.
Like you, I recently decided to change the hoses on my 1976 Glenbrook
that I purchased new in October 1975. My air-conditioning system had not
held refrigerant very well for several years. The pressure switch was one
of the first components I removed. Its "O" ring crumbled when the switch
was removed, and I could not help wondering how the system held refrigerant
at all as I disassembled the hoses, because the other "O" rings were not in
much better shape. In short, all of the seals that "see" refrigerant
pressure are more than 20 years old, and they need to be replaced to obtain
a leak-free air-conditioning system.
This leaves the compressor decision. Re-manufactured compressor bodies
are relatively inexpensive, but many old coil, clutch and pulley assemblies
should not be reused. New compressors come completely assembled with new
coil, clutch and pulley assemblies, making them very easy to install
through the right-front wheel well opening, if you choose a new compressor,
make sure its oil is compatible with R12 refrigerant. Also, a new belt that
is one-inch shorter than the old belt will have to be installed on most
engines, because the belt rides lower in the new pulley. A Gates 7612 belt
will do the job on a 455-cid engine, and a Gates 7590 belt will do the job
on a 403-cid engine.
- ---------------------------------------------------------------------------
I can't find any part numbers in any of the parts cross references,
Motorhome Marketplace or GMCnet archives.
If you need to purchase the GMC Motorhome News publication, there's
instructions at:
http://gmcmotorhomeindex.homepage.com/gmcnews/
hth
bdub
>Anyone have their GMC Motorhome News quarterlies close by? IIRC, this was
>covered a year or so ago. Don't recall if they specified any part numbers
>tho'.
>
>Patrick
>
> >
> > Tried ordering a new rec/dryer and expansion valve from NAPA
> > using the part numbers on the GMCmart. NAPA guy could not
> > find these and when I asked for the parts using a 73 Toronado,
> > he also couldn't find them. Anybody ever get a rec/dryer and
> > exp. valve from NAPA or Autozone, what p/n's.
