MACS Monthly Newsletter - 2020 - MAR8

FCA

tiple colors of highlighters to
trace power circuits, grounds,
signal wires, bussed serial data
(i.e. CAN), inputs and outputs to
try and break down the schematic
to make it more understandable.
Jorge Menchu with AES Wave
has taught a class at MACS conventions in the past on the art of
doing this in order to make complex schematics easier to understand.
3. Critical
Thinking:
Compare what you can verify
to what is written. For example,
you read in the service manual's
theory of operation that the A/C
Figure 11: What really turns on the compressor clutch? The official Chrysler "Tech clutch is controlled by the PCM.
Connect" website for this 2013 Dodge Grand Caravan gives an accurate list of PCM Then after reviewing system schesensor inputs. That's where the accuracy fades. Notice the PCM sensor outputs show- matics you see a ton of A/C reing an Air Conditioning Clutch Relay? Schematics and module pin outs tell the real lated inputs connected to another
story.
module like an FCA's TIPM. You
also see there is a TIPM output circuit connected directly to the combest engineers and vehicles going. These kinds of errors
are, however, problematic within the industry in general. pressor clutch. You look at the connector pinouts for all
Rather than obsess over why the OEMs are sometimes A/C clutch operation related modules and the pinouts
lacking in service information accuracy, let's explore seem to back up the schematics. In this case you can consome things you can do when you discover such prob- clude the theory of operation write up is bogus; the PCM
lems. Obviously if time permits, register any omissions doesn't control the clutch. Don't forget to use scan data in
/ inaccuracies with your ESI supplier. If you're using the order to see inputs and outputs (either bussed or direct)
factory service manual, file your request / complaints to validate your suspicions that the theory of operation is
there. In the meantime, you've got a vehicle to diagnose incorrect. In my example case on the 2013 Dodge Caraand repair. Follow these steps to get the diagnostic job van, the PCM does NOT turn on the clutch - the TIPM
does!
done when the book is wrong:
Don't let service manual inaccuracies discourage you.
As they say, "To err is human, to forgive divine." Everyone makes mistakes in the automotive business. From
OEM designers to factory service engineers to technicians in the service bay. The secret to success is accurately
identifying mistakes and make the repair. Just consider
mistakes as hidden opportunities. After all, without mistakes in one form or another, we'd be out of business in
the auto repair profession! n

1. Acquire and Organize Service Information:
Print out (and organize) all related theory of operation
write ups, schematics and module connector pin outs. If
your aftermarket ESI source (i.e. Mitchell or ALLDATA)
has glaring omissions or errors, visit www.OEM1STOP.
com and purchase an affordable (often only $20-$30) short
term subscription to that OEM's factory service information.
2.
Analyze & Simplify the Information: Use mul-

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.

March 2020

MACS Service Reports

https://www.oem1stop.com/ https://www.oem1stop.com/ http://www.macsw.org

MACS Monthly Newsletter - 2020

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