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Yes, The Service Port Cap Really is the Primary A/C Seal!

For years, we have been told that the primary seal for the A/C service ports lies in the service port cap. Yet day after day, technicians let vehicles leave the shop after service without service port caps. In this example, we look at a 2003 Subaru Baja. This was brought into MACS for evaluation after a long-term (1 year) test of a prototype component.

The Background:

This vehicle was purchased by the current owner in late 2017 with 51K miles on the odometer.  After purchase, the owner took it to Iezzi’s Auto Service in Reading, PA. There it received a new timing belt and head gaskets. As part of this work, A/C expert Tim Iezzi, inspected the A/C system, changed the seals, recharged, and confirmed proper operation.

Fast forward to late summer 2022 when a prototype component was installed for a one-year test with 75K miles on the clock. During the installation, 630 grams of R-134a refrigerant was recovered from the system whose label indicates a refrigerant charge specification of 600 -700 grams. Having recovered this much refrigerant with a standard SAE J2788 A/C Service Machine, the system was deemed free of leaks although, the service port valve cores were not independently tested for leakage.

In September of 2023, the prototype component was removed. This required the recovery of the refrigerant from the system. Using an Inficon D-Tek Stratus leak detector that was checked for proper operation by passing it over the uncapped windshield washer bottle, the service port caps were checked for leaks. No leaks were found. The caps were then removed, any accumulated refrigerant was dispersed, and then this happened….

Checking the Service Ports

Both the low and high sides clearly indicated that the service ports were indeed leaking. If not for the service port caps, this would have resulted in poor cooling performance.

The root cause is the valve core. These valve cores have a limited number of depressions before they need to be replaced. In some cases, the first depression can break the seal and making leakage a, “When, Not If”, scenario.

Shop Owners and Service Technicians

Allowing a vehicle to leave without service ports after touching the A/C system is an invitation for a customer return. Caps are inexpensive and valve cores take a mere minute or two to change during service.

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