MACS Monthly Newsletter - 2020 - JAN6

rubber poppet that seals against a cone (Figure 13). Also
known as the integrated valve, these high flow "replaceable service ports" were a popular choice for high side
access from the 90s to the early teens with GM and Chrysler. Ford and VW used both high and low side versions,
although today manufacturers tend to favor 8mm and
10mm valve cores.

mers that are used in making seals, most of which have
been defined by the individual car companies as compatible with their specific refrigerant / oil combinations. For
example, you can get the same 10mm core made with
many diﬀerent seal materials. So, while there are only a
few number of "hard parts" the wide variety of seal materials available for each valve core increases the number
of product variations available.

Seal materials

The tiny seals used on valve cores (and most other A/C
system-specific seals for that matter) come in a wide variety of materials for various applications. In general, the most
popular choices include:
a. Chloroprene: Commonly referred to as Neoprene, this compound is a traditional A/C seal
material with good compatibility with all mobile
A/C refrigerants and both mineral and PAG oil.
It's not recommended for high-temperature applications over 120°C. It's also a popular choice
for making fishing waders and wetsuits!
b. HNBR: The most broadly capable of the various compounds, HNBR (hydrogenated nitrile butadiene rubber) is widely known for retaining its
strength and physical properties after long term
exposure to chemicals, oils and heat (and as such
is recommended for system temperatures up to
150°C). HNBR is compatible with all mobile A/C
refrigerants, along with mineral, PAG and POE
oils. Older versions of HNBR had issues with
low-temperature applications, but newer varieties give good performance down to -40°C. This is
by far the most common seal material being used
in MAC systems today. And if you wear disposable gloves, chances are they're nitrile!
c. EPDM: Ethylene propylene diene monomer
rubber is a standard by the VDA (German Association of the Automotive Industry), so you'll see
some EPDM materials coming on European cars.
A synthetic compound with the broadest operating temperature range (up to 180°C in extreme
situations), it works with all mobile refrigerants,
but ONLY with PAG oil. It cannot be used with
mineral oil and has shown compatibility issues
with some POE formulations. It also makes an
extremely durable roofing membrane (i.e. rolls of
rubber roofing at the home center).
We'll also mention here that there are a few vehicles using FKM compounds, which is a family of fluoroelastomer
materials that includes Viton (a name you're likely familiar
with as it's been widely used in the manufacture of o-rings,
seals and rubber gloves). Although it's generally not recommended for A/C seals as it's not going to work with POE
oils, and its permeation rates are a little higher than some
other seal choices.

Figure 13: Primary Seal: The service coupler's pin on
your manifold gauge set or R/R/R machine can depress an
integrated valve's poppet in the same way that it does a conventional valve core's pin.

Steve Schaeber

If a primary seal develops a leak, you don't replace
the poppet. Instead the whole valve is removed using an
octagonal socket. Two sizes are available to fit both high
and low side integrated valves. See Figure 14.

Figure 14: Don't be that guy who grabs pliers to replace
an integrated valve! Special "octagonally" shaped sockets are widely available to remove and properly install the
new valve (which requires torqueing to precise specifications to ensure a quality seal.
Some valve core manufacturers have multiple diﬀerent part numbers in their catalogs to choose from, which
causes a lot of diﬃculty for people in service. Normally
you should try to use the correct core that originally came
with the vehicle, that is, to buy it from the OE as a service
part. The reason is because of the many diﬀerent elasto-

January 2020

MACS Service Reports

MACS Monthly Newsletter - 2020

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