MACS Monthly Newsletter - 2020 - AUG4

Nissan-techinfo.com

Figure 6: Threaded nut fittings have been much modified over the years. Nissan made these changes over 20 years ago.
Note the ways the O-ring could be improperly positioned, even with the correct O-ring.

in a rigid section of refrigerant line, such sealing eventually may leak. Seals take a set as the system is unused in
cold weather, and deteriorate as the system goes through
temperature changes. Additionally, debris from wear of
internal parts in the compressor can cut, crush and twist
sections of an O-ring seal. Contaminants from outside
the A/C refrigeration system can enter it and also affect
elastomer seals. See Figure 5.
So, when a joint leaks and you take it apart and find deterioration of the elastomer, it should be no surprise. But
you can't just replace the seal and reassemble the joint.
You also should inspect the joint for any debris and carefully clean it with a plastic tool. If the piping has any deep
scratching, it should be replaced. These rules also apply
to the compressor seal bore. Yes, we know the thought
of replacing a compressor that is mechanically operating
in normal manner, but has a deep scratch in the sealing
bore, is likely to evoke an "are you kidding" response.
However, if it was leaking from that joint, what's the option? Perform some jerry-rigged approach that adds sealing material? Deep down, you know that even if it seals
for a while, the repair is unlikely to be durable.
A couple of other parts may leak and present a similar
quandary: The condenser and the expansion valve if the
joints are beyond careful cleaning and re-use. Although
the expansion valve isn't quite pocket change, it's not so
expensive that one should hesitate replacing it. The condenser presents a price problem, however, in the same
category (even if not as expensive as a compressor). In
this case you might be able to use a repair fitting (such
as a Lokring swage connector or AirSept "smart splice."
Depending on the vehicle and access to the condenser, it
could be a durable repair.
If all the joint needs is a new O-ring, you still shouldn't
be "casual" about it. Unless you have a replacement that
you know is a match, it's worth getting a make/model

August 2020

O-ring kit. The investment will be modest, and it will be
well worth it. If you open a joint, the seal should never be
re-used, so a kit can provide sealing at all the refrigerant
line joints that produce any indication of even a small
leak.
There have been many types of A/C joint fittings over
the years, from the simple tube-and-nut with O-ring to
the teardrop (cam-lobe-shaped) the "peanut," the plastic clamped (first used by Toyota and later by several
makes), the gasket-like that form what we call the sealing
washer, and of course the spring-lock coupling. If the fitting is sealed by an O-ring or two or even three, you can't
just replace with what seems to be the same size. The difference in dimensions between the right and wrong Oring is not necessarily apparent to the naked eye, and a
joint that won't seal with the new O-ring is often caused
by the wrong size.
Also, a common issue is an O-ring that doesn't seat
quite the same as the original. And in some cases, the
reason is that the replacement O-ring is just a hair different in dimensions (Figure 6). Or a change was made (the
1998 Nissan fitting as a classic example) so an O-ring has
to be positioned differently on a flange. Sealing washers also can be prone to this issue, because they typically
leave a hairline gap and technicians that know this have
mistakenly installed a slim line washer, which leaves a
larger gap and won't seal well at all.

SPRING-LOCK COUPLINGS

There are many millions of spring-lock couplings on
vehicles still in use, and they're not just Ford products.
You'll find them on lots of Chrysler products and Hyundai-Kia models too. If as noted earlier in this report, the
coupling is "supported," that is in a section of refrigerant
line that is clamped to the vehicle body at both ends, the
coupling should not be prone to the flexing that contrib-

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MACS Monthly Newsletter - 2020

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