MACS Monthly Newsletter - 2021 - OCT1

Service Reports
MOBILE AIR CLIMATE SYSTEMS ASSOCIATION TM
By Paul Weissler, MACS Senior Technical Correspondent
Diagnostic Techniques: Time vs Cost
Automotive service technicians often disagree on repair
and diagnostic techniques, including A/C and cooling system
work, and that includes those of us who publish our recommendations
in MACS Service Reports.
However, this doesn't mean that those on one side or
another are wrong, but that our belief system has different
structural components. In plain English this means that we're
placing the emphasis on different aspects of the situation, a
different mix of vehicles that we're servicing, including a customer
base with different budgetary and time constraints to
produce a repair. Some diagnostic approaches cost more
than others, but may produce faster answers, and some customers
may be willing to pay the price.
Example: The A/C has a full charge but isn't cooling. One
way of tracing the problem is to replace parts -expensive but
depending on the symptoms may produce a quick fix--or of
course it may not, resulting in large parts bills and still no
cooling. Which is why we at MACS Service Reports usually
prefer proof before parts replacement, even when it may slow
down things.
Or there's loss of A/C cooling from an apparent leak. This is
perhaps the most common complaint and also the one with
the greatest variation in service approach.
There's a heat wave, there was no OE trace dye installation,
the leak location isn't obvious, and the customer wants cool
air RIGHT NOW. A shop would often just fill the system with
refrigerant and a dose of trace dye, and send the car on its
way, to come back when the A/C stops cooling. Hopefully by
then a dye trace will identify the location and permit a durable
repair in the most economical way. The best information we
have is that, despite the increased use of compressors that
trap most of the refrigeration oil, the dye/oil mixture should
circulate sufficiently in a system with modest leakage, to
reach and escape a leak point, and be visible.
But what if it doesn't? R-1234yf is retail-priced at about
$100/lb. (and wholesale about $70/lb.). So you may be
among the shops that have been happy to charge a system
with a couple of pounds of R-134a, at just $5-7/lb., and send
the car out the door. The motorist may want a lower-cost approach
on an R-1234yf system, but still with the reasonable
likelihood of an immediate answer. Further, if your shop just
sank $8k or more into a new R-1234yf machine, you obviously
can't perform recovery/recycle/recharge service just for the
price of refrigerant and the dose of dye. In fact, shops with an
expenditure of as little as $4k in an R-134a machine, couldn't
justify a similar investment of time-and-material on an R-134a
vehicle. v
October 2021
CONTENTSSAE
Certified Leak Detectors:
Best Choice For Diagnosis Now, At Low Cost ................................................... 2
Trace Dye Moves To The Forefront Again (With A Big If) ................................. 3
That Refrigerant Flow Sensor ................................................................................. 4
Refrigerant Contamination On New Cars-Huh? ............................................... 5
Cause Of A/C Failure We Often Forget ................................................................. 6
Meet The " LIN " Bus ...................................................................................................7
Effects Of Ageing ...................................................................................................... 8
MACS Service Reports is the official technical publication of the
Mobile Air Climate Systems Association, P.O. Box 88, Lansdale, PA
19446. The material published in MACS Service Reports expresses
the views of the contributors and not necessarily that of MACS. Every
attempt has been made to ensure
October 2021
1
the accuracy of the content of MACS Service Reports. MACS, however,
will not be responsible for the accuracy of the information published
nor will MACS be liable in any way for injury, labor, parts or
other expenses resulting from the use of information appearing in
MACS Service Reports.
MACS Service Reports

MACS Monthly Newsletter - 2021

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