MACS Monthly Newsletter - 2017 - JUN8

6. Don't forget other causes such as leaking
alternator diodes. Test for this by removing
the heavy gauge output cable at the alternator to see if the drain goes away.
7. Finally, hopefully you pulled DTCs from
every module on board before jumping very
deep into such a problem. Sometimes the
pattern of U-codes (communications) gives
you a clue when an electronic module is to
blame for the parasitic drain.

sory activations, opening and closing the
trunk, glove box and hood looking for sticky
switches that might cause a light to stay on
when it should be off, etc.) in order to try to
get an intermittent parasitic drain to occur.
3. If there is a larger than normal parasitic
drain, the ohmmeter will read a 'false positive'. A false positive would be a resistance
reading that is much higher than expected.
Several ohms up to 50 or more ohms (Fig. 14)
depending on which way you've connected
your leads, an ohm reading that is negative!
4. If the outcome to step 3 is positive (more
than the expected ohms of resistance in a
known good ground circuit) it's time to connect your ammeter / parasitic drain switch,
etc. to verify / quantify the drain.
5. Next follow up with narrowing down the
list of possible battery drain suspects by performing the fuse voltage drop test mentioned
earlier.

Finally, many techs are experimenting with infrared thermal imaging equipment to determine which
fuse (or electronic module) is the cause of a phantom battery drain. The temperature signature of
the culprit is slightly higher than its surroundings
thereby providing picture perfect evidence. The
same tool has many other uses ranging from HVAC
diagnostics to misfires. Not a bad idea. Since technology isn't standing still for us, we need to keep
our tools and techniques moving as well! ■

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.

June 2017

8

MACS Service Reports


http://www.macsw.org http://www.macsw.org

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

MACS Monthly Newsletter - 2017 - JAN1
MACS Monthly Newsletter - 2017 - JAN2
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MACS Monthly Newsletter - 2017 - FEB1
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MACS Monthly Newsletter - 2017 - MAR1
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MACS Monthly Newsletter - 2017 - MAR8
MACS Monthly Newsletter - 2017 - APR1
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MACS Monthly Newsletter - 2017 - APR8
MACS Monthly Newsletter - 2017 - MAY1
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MACS Monthly Newsletter - 2017 - MAY5
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MACS Monthly Newsletter - 2017 - MAY7
MACS Monthly Newsletter - 2017 - MAY8
MACS Monthly Newsletter - 2017 - JUN1
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MACS Monthly Newsletter - 2017 - JUN3
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MACS Monthly Newsletter - 2017 - JUN5
MACS Monthly Newsletter - 2017 - JUN6
MACS Monthly Newsletter - 2017 - JUN7
MACS Monthly Newsletter - 2017 - JUN8
MACS Monthly Newsletter - 2017 - JUL1
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MACS Monthly Newsletter - 2017 - JUL3
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MACS Monthly Newsletter - 2017 - JUL5
MACS Monthly Newsletter - 2017 - JUL6
MACS Monthly Newsletter - 2017 - JUL7
MACS Monthly Newsletter - 2017 - JUL8
MACS Monthly Newsletter - 2017 - AUG1
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MACS Monthly Newsletter - 2017 - AUG5
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MACS Monthly Newsletter - 2017 - AUG7
MACS Monthly Newsletter - 2017 - AUG8
MACS Monthly Newsletter - 2017 - SEP1
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MACS Monthly Newsletter - 2017 - SEP8
MACS Monthly Newsletter - 2017 - OCT1
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MACS Monthly Newsletter - 2017 - OCT3
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MACS Monthly Newsletter - 2017 - OCT5
MACS Monthly Newsletter - 2017 - OCT6
MACS Monthly Newsletter - 2017 - OCT7
MACS Monthly Newsletter - 2017 - OCT8
MACS Monthly Newsletter - 2017 - NOV1
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MACS Monthly Newsletter - 2017 - NOV3
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MACS Monthly Newsletter - 2017 - NOV5
MACS Monthly Newsletter - 2017 - NOV6
MACS Monthly Newsletter - 2017 - NOV7
MACS Monthly Newsletter - 2017 - NOV8
MACS Monthly Newsletter - 2017 - DEC1
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MACS Monthly Newsletter - 2017 - DEC3
MACS Monthly Newsletter - 2017 - DEC4
MACS Monthly Newsletter - 2017 - DEC5
MACS Monthly Newsletter - 2017 - DEC6
MACS Monthly Newsletter - 2017 - DEC7
MACS Monthly Newsletter - 2017 - DEC8
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