MACS Monthly Newsletter - 2020 - FEB1

©

Total Vehicle Climate and Thermal ManagementTM

February 2020

By Paul Weissler, MACS Senior Technical Correspondent

DON'T BE SURPRISED BY THIS
mate Control Housing, which is another matter. Presumably, Ford spent somewhat more to build a lot of quality
into the housing and expects the housing to last a long,
long time.
Of course, the trouble code may be caused by a wiring issue from the evaporator temperature sensor. Ford
service information provides pinpoint tests at the FCIM
(Front Controls Interface Module), so before any highlyinvasive work at the Climate Control Housing, perform
the pinpoint tests. If testing leads to a "replace evaporator
temperature sensor," well you've done your homework
and now it's time to let the motorist in on the bad news.
Evaporators engineered for R-1234yf are notably more
durable designs, so they should last. But no part is forever, and some lesser components do get though the manufacturing process, and if an evaporator starts to leak, the
replacement will not be cheap. The factory flat rate time
is 10.5 hours plus you can add in another 1-1/2 hours
for recharging the system. The Climate Control Housing
is about $660, so you can see the job ticket approaching
$2000. See Figure 1.
An aftermarket manufacturer likely could offer an
evaporator kit for somewhat less. But a price tag of $660
for a fully-assembled housing with just a few transferover parts seems pretty reasonable. Taking apart the old
housing and installing a replacement evaporator core,
carefully fitting a core perimeter seal, then reassembling
meticulously, is not going to be a quick job.

When the A/C fails to cool, but there's no refrigerant
leak, and system pressures seem normal, a technician has
to face the possibility of an electrical issue. And if he has
a high-feature scan tool, he may pick up a trouble code to
guide diagnosis. In the case of a late-model Ford product
(phase-in since 2014) and a trouble code for the evaporator temperature sensor, you find either B1B71-11 for the
sensor shorted to ground or B1B71-15 for an open circuit
or short to battery.
No sweat now, you may be thinking. Many evaporator temperature sensors are replaceable from under the
dashboard, after removing some trim pieces and underdash insulating pad.
No such luck with recent Ford systems. The sensor is
built into the evaporator, which we suspect an engineer
decided would prevent the problem of the sensor coming
loose in between the evaporator fins or something similar.
It's the type of assembly that has been proven to improve
assembly quality. And we suspect it lowers warranty
costs. Years ago, Ford built the evaporator into a sealed
case on some models. It certainly improved assembly
quality - no condensate leaks from the hot-welded case.
And although an evaporator leak meant the entire case
had to be replaced, Ford priced the case reasonably and
the design did not raise a lot of complaints.
However, if the vehicle is out of warranty on a latemodel today, it's another matter. On most models, the
evaporator is available only as part of the complete Cli-

ALSO INSIDE THIS ISSUE:
REAR HVAC: WHAT TO DO? ............................................................................................................................................ 2
A TOUGH DECISION? . ...................................................................................................................................................... 3
BLOWER DIAGNOSIS SHOULD INCLUDE WIRING DIAGRAM . .................................................................................... 5
BAD LUCK OR TECHNICIAN'S FAULT.............................................................................................................................. 5
A NEW WORLD OF COOLING SYSTEMS......................................................................................................................... 6
A/C CUTS OUT.................................................................................................................................................................... 8

MACS Service Reports is the official technical publication of the Mobile Air Conditioning Society Worldwide, Inc., 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

February 2020	

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
Worldwide be liable in any way for injury, labor, parts or other expenses resulting
from the use of information appearing in MACS Service Reports.

1	

MACS Service Reports



MACS Monthly Newsletter - 2020

Table of Contents for the Digital Edition of MACS Monthly Newsletter - 2020

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