MACS Monthly Newsletter - 2017 - NOV8

fast service and the dealer means a two-week (or longer) wait for an appointment, and the fear that anything the dealer does will be very expensive.
In this case the car wasn't new; a 2011 Cadillac SRX,
roughly seven years old, long out of warranty and
over 90,000 miles on the odometer. The problem was
one often heard: with ambient temperatures in the
mid to upper 70's°F, A/C air from the registers wasn't
very cold on the driver's side (lowest was 66°F), but
does produce reasonable cool (48°F) on the passenger's side. Okay, one side high, one low is typically

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an indication of low refrigerant, but the shop did an
evac-and-recharge, and is sure the charge is normal.
The only code is for the sunload sensor, and most
shops know that if you don't run a specific test for the
sensor, it may log a code.
Using his scan tool, the technician next cycled the
two temperature doors, and that seemed to confirm
they both were operating normally, although the technician (overthinking the situation) suspected that perhaps the driver's side door actuator was responding,
but maybe the door itself was not. Yes, that happens,
but not in this case, which the technician basically verified by manually moving the flap door with a screwdriver. He also confirmed that if he moved it to full
heat, he got heat. So presumably when he moved it to
full cold, he should have gotten something better than
just below ambient temperature. He then suspected
that even though the door linkage was moving normally, maybe the door itself was not, but even with a
borescope he couldn't find a location that would give
him a view of the door in motion. At this point the motorist decided that the car had an expensive malady
and he had been contemplating replacing it anyway,
so no repair.
Had he checked the service bulletins, the technician
would have found one that was as exact a match for the
problem as you'll find: 2011-12 Cadillac SRX, and air
coming from the driver's side A/C registers is warmer
than the passenger's side, with the high-pressure side
gauge reading somewhat lower than "expected." Inasmuch as high-side pressures are "normal" within
a substantial range, the technician might not pick up
much of a clue from the gauge readings. The bulletin
does tell the technician to first make sure the doors are
moving, including to full cold position (he did that),
and there's a full refrigerant charge. With all that information, the fix is to replace the receiver-dryer, which
is a cylindrical type attached to the condenser, so the
condenser must be removed for the job. See Figure 12.
The root cause, actually a rare event in this era of
moisture-absorbing PAG oil, is that the desiccant is
saturated with moisture and that restricts refrigerant
flow, explaining why the symptom simulates low refrigerant. But apparently the moisture saturation of
the desiccant occurred prior to installation. ■

Figure 12: Service bulletin for 2011 Cadillac SRX covers situation that simulates low refrigerant but actually is caused by desiccant bag in cylindrical
receiver-dryer on side of condenser being saturated with moisture, restricting
refrigerant flow.

MACS Service Reports is published monthly by the Mobile Air Conditioning Society
Worldwide. It is distributed to members of MACS Worldwide and is intended for
the educational use of members of the automotive air conditioning service and
repair industry. Suggestions for articles will be considered for publication, however,
MACS Worldwide reserves the right to choose and edit all submissions.

Editors:
Elvis Hoffpauir, Steve Schaeber
Production Designer:
Laina Forcey
Manager of Service Training:
Steve Schaeber
Mobile Air Conditioning Society Worldwide
P.O. Box 88, Lansdale, PA 19446
Phone: (215) 631-7020 * Fax: (215) 631-7017
Email: membership@macsw.org * Website: www.macsw.org

Unless otherwise noted, all photos/art by author.

November 2017

MACS Service Reports

http://www.snapontools.com http://www.macsw.org

Table of Contents for the Digital Edition of MACS Monthly Newsletter - 2017