MACS Monthly Newsletter - 2017 - NOV2
motorcraftservice.com
Figure 1: A/C circuit on 2003 Lincoln Navigator runs from Central Junction Box, goes through control panel (labeled Position Selector Switch Assembly), into A/C high pressure switch, and exits on RD/YE (red/yellow wire on circuit No. 441).
November 2017
motorcraftservice.com
the HVAC control panel ("Position Selector Switch
Assembly") and after the A/C high pressure switch
at lower right, the electrical control for the refrigeration system continues on another circuit (Figure 2).
The answer actually was pretty simple, and we suspect an experienced technician reading this will be
smirking: a thermostatic switch. Yes, that's just another term for a type of evaporator temperature sensor
(actually an on/off switch to cycle the compressor).
And in this case, it was not inserted in the evaporator,
but was on the expansion valve, along with the wiring diagram's plainly-labeled electro-mechanical ambient-low pressure switch. He jumpered the switch,
but all he actually was bypassing was that ambientlow switch, as the thermostatic switch (which actually controlled the cycling) was a solid-state sensor
with its own connector. Your service information system should have the pinpoint tests, so we won't repeat them here. The thermostatic sensor should cycle
on/off to control A/C clutch operation in the 36-38°F
range. This sensor does tend to drift over the years,
so you may find it necessary to replace it before total
failure to correct poor A/C performance. The sensor
is wired to the Powertrain Control Module, to prevent A/C ice-up. It completes the circuit to the PCM
at 36-38°F to engage the clutch when the refrigerant
temperature rises or breaks the clutch circuit when
the temperature drops. All pretty simple, if you know
it's there and what it does. ■
Figure 2: Although the next diagram page has two schematics, this is the one
that continues the refrigeration control circuit. Notice that the expansion valve
has two switches; ambient-low protection switch and a solid state "microprocessor" labeled a thermostatic switch. This is the sensor for A/C clutch cycling.
2
MACS Service Reports
http://www.motorcraftservice.com
http://www.motorcraftservice.com
Table of Contents for the Digital Edition of MACS Monthly Newsletter - 2017
MACS Monthly Newsletter - 2017 - JAN1
MACS Monthly Newsletter - 2017 - JAN2
MACS Monthly Newsletter - 2017 - JAN3
MACS Monthly Newsletter - 2017 - JAN4
MACS Monthly Newsletter - 2017 - JAN5
MACS Monthly Newsletter - 2017 - JAN6
MACS Monthly Newsletter - 2017 - JAN7
MACS Monthly Newsletter - 2017 - JAN8
MACS Monthly Newsletter - 2017 - FEB1
MACS Monthly Newsletter - 2017 - FEB2
MACS Monthly Newsletter - 2017 - FEB3
MACS Monthly Newsletter - 2017 - FEB4
MACS Monthly Newsletter - 2017 - FEB5
MACS Monthly Newsletter - 2017 - FEB6
MACS Monthly Newsletter - 2017 - FEB7
MACS Monthly Newsletter - 2017 - FEB8
MACS Monthly Newsletter - 2017 - MAR1
MACS Monthly Newsletter - 2017 - MAR2
MACS Monthly Newsletter - 2017 - MAR3
MACS Monthly Newsletter - 2017 - MAR4
MACS Monthly Newsletter - 2017 - MAR5
MACS Monthly Newsletter - 2017 - MAR6
MACS Monthly Newsletter - 2017 - MAR7
MACS Monthly Newsletter - 2017 - MAR8
MACS Monthly Newsletter - 2017 - APR1
MACS Monthly Newsletter - 2017 - APR2
MACS Monthly Newsletter - 2017 - APR3
MACS Monthly Newsletter - 2017 - APR4
MACS Monthly Newsletter - 2017 - APR5
MACS Monthly Newsletter - 2017 - APR6
MACS Monthly Newsletter - 2017 - APR7
MACS Monthly Newsletter - 2017 - APR8
MACS Monthly Newsletter - 2017 - MAY1
MACS Monthly Newsletter - 2017 - MAY2
MACS Monthly Newsletter - 2017 - MAY3
MACS Monthly Newsletter - 2017 - MAY4
MACS Monthly Newsletter - 2017 - MAY5
MACS Monthly Newsletter - 2017 - MAY6
MACS Monthly Newsletter - 2017 - MAY7
MACS Monthly Newsletter - 2017 - MAY8
MACS Monthly Newsletter - 2017 - JUN1
MACS Monthly Newsletter - 2017 - JUN2
MACS Monthly Newsletter - 2017 - JUN3
MACS Monthly Newsletter - 2017 - JUN4
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
MACS Monthly Newsletter - 2017 - JUL2
MACS Monthly Newsletter - 2017 - JUL3
MACS Monthly Newsletter - 2017 - JUL4
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
MACS Monthly Newsletter - 2017 - AUG2
MACS Monthly Newsletter - 2017 - AUG3
MACS Monthly Newsletter - 2017 - AUG4
MACS Monthly Newsletter - 2017 - AUG5
MACS Monthly Newsletter - 2017 - AUG6
MACS Monthly Newsletter - 2017 - AUG7
MACS Monthly Newsletter - 2017 - AUG8
MACS Monthly Newsletter - 2017 - SEP1
MACS Monthly Newsletter - 2017 - SEP2
MACS Monthly Newsletter - 2017 - SEP3
MACS Monthly Newsletter - 2017 - SEP4
MACS Monthly Newsletter - 2017 - SEP5
MACS Monthly Newsletter - 2017 - SEP6
MACS Monthly Newsletter - 2017 - SEP7
MACS Monthly Newsletter - 2017 - SEP8
MACS Monthly Newsletter - 2017 - OCT1
MACS Monthly Newsletter - 2017 - OCT2
MACS Monthly Newsletter - 2017 - OCT3
MACS Monthly Newsletter - 2017 - OCT4
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
MACS Monthly Newsletter - 2017 - NOV2
MACS Monthly Newsletter - 2017 - NOV3
MACS Monthly Newsletter - 2017 - NOV4
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
MACS Monthly Newsletter - 2017 - DEC2
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
https://www.nxtbook.com/nxtbooks/macs/servicereports_2022
https://www.nxtbook.com/nxtbooks/macs/servicereports_2021
https://www.nxtbook.com/nxtbooks/macs/servicereports_2020
https://www.nxtbook.com/nxtbooks/macs/servicereports_2019
https://www.nxtbook.com/nxtbooks/macs/servicereports_2018
https://www.nxtbook.com/nxtbooks/macs/servicereports_2017
https://www.nxtbook.com/nxtbooks/macs/servicereports_2016
https://www.nxtbook.com/nxtbooks/macs/servicereports_2015
https://www.nxtbookmedia.com