MACS Monthly Newsletter - 2020 - JAN3

But a more careful approach may yield better overall results. See Figure 5:
a second time.
d. After clearing the port of retained refrigerant vapor, slowly pass the sniﬀer probe across and 2 inches
above the port opening. If the detector gives a consistent and repeatable indication, then there is a leak in
the port.
4. If there is a leak within the port, it's important to
find and correct the cause of the leak.
a. Retighten the valve core to the specified amount
(see installation torque on page 7) and re-check for
leaks. Occasionally a core leaks because it has vibrated
loose or was misassembled. Remove the core if a leak
is detected after retightening.
b. Look for contamination on the valve seal, look at
the condition of the seals, and the smoothness of the
internal surfaces of the port. Based on experience,
some of the more frequent causes of valve leaks are:
i. Contamination: The valve core is the smallest passage through which the system is evacuated. Contamination from many sources can become lodged in the
valve causing a leak. If the valve is operated on the
road without a cap, road dust and debris may have
been introduced into the valve during an earlier service action. If the leak was caused by contamination,
then the port must be cleaned as well as possible and
the system flushed prior to recharging.
ii. Valve degradation: There are many valve designs
and versions available in the market, but not all will
work in all systems. Use of valves with the wrong rubber compound may be incompatible with the refrigerant or oil used, or be not suitable for the temperatures
in the vehicle. If the leak was caused by a degraded
valve, it must be replaced with the correct version
valve. Universal valve sets are available which have
been designed for use in the greatest variety of systems.
iii. Valve damage: A misadjusted service coupler
may damage the valve and cause it to subsequently
leak. We recommend that all service couplers be periodically examined to assure that the presser pin is not
damaged or misadjusted. SAE J639 gives the proper
depressor pin length for the various refrigerants in
use.
iv. Defective port machining: This would be the most
diﬃcult defect to find and correct in the field. Service
technicians do not have the instruments required to assess valve port quality. If none of the three potential
causes listed above seemed to be the cause of the leak,
and a new valve core does not correct the leak, then
the cause is most likely a defective port. The corrective
action in this case is to remove and replace the entire
line, with a new service port and valve.
v. In all cases we recommend that if the valve core
is removed from the port it should be replaced with
a new core. Over time the external rubber seal of the
core takes a "set" and may not seal with the same robustness as a new one.

Steve Schaeber

Figure 5: Leak testing of the vehicle should be conducted
with an SAE J1627-compliant halogen leak detector, "sniﬃng"
all potential leak sources. If there is no indication of leakage
around the cap, then the service port is NOT the source of the
leak. If a leak is indicated, the next step will be to remove the cap
and test the valve. We suggest the following process:
1. After removing the cap, look closely at the condition of the space under the cap (Figure 6). The presence
of refrigerant oil or fluorescent dye is an indication that

Figure 6: Inspect under and inside the cap for an oring. Make sure it's in good condition and did not stick
to the port mouth (don't lose it!). Also check for oil / dye
inside the port.

Steve Schaeber

there is leakage past the valve. Look also for the presence
of contaminants that may have been introduced at previous recharging operations.
2. If there was no cap installed, clean the external surfaces of the port so that later, when recharging, the coupler can seal properly to the port. See Figure 7.

Figure 7: We often see ports without caps, some more or
less dirty than this. Clean the inside (to avoid contaminating the refrigerant /oil) and outside (to ensure a good
sealing surface for your service coupler's o-ring).
3. When utilizing a halogen leak detector:
a. First, be sure the leak detector is set to detect the
refrigerant used in the system. Many halogen leak detectors are calibrated for several common refrigerants,
be sure you are set to detect the correct one.
b. Next, set the leak detection scale. We recommend
using a leak scale no less than 10 grams per year. This
will allow searching for significant leaks with less possibility of false indications which occur with very low
sensitivity settings.
c. It is important when sniﬃng the valve that the
space under the cap be evacuated of retained refrigerant. Accordingly, blow out the port opening with compressed air blast, wait 2 minutes and blow out the port

January 2020

MACS Service Reports

MACS Monthly Newsletter - 2020

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