Pinpoint Test K: The Air Conditioning (A/C) Is Inoperative
Refer to Wiring Diagrams Cell
55
, Automatic Climate Control System for schematic and connector information.
Normal Operation
Under normal operation, when A/C is requested, a message is sent over the bus from the electronic automatic temperature control (EATC) module, through the instrument cluster, to the
powertrain control module (PCM). The PCM receives input from the A/C cycling switch through circuit 883 (PK/LB). Voltage is provided to the A/C cycling switch through circuit 1040
(RD/BK)/348 (VT).
The PCM provides a ground for the A/C clutch relay coil through circuit 73 (OG/LB). The A/C clutch relay coil receives voltage through circuit 391 (RD/YE). Voltage for the A/C clutch relay
switch is provided through circuit 1810 (LG/OG). When the relay is activated, voltage is supplied to the A/C clutch solenoid through circuit 321 (GY/WH). Ground is supplied for the A/C
clutch through circuit 57 (BK).
The A/C cycling switch is used for A/C compressor cycling. The switch is used by the PCM to turn off the A/C compressor before the line pressures are low enough to drop the evaporator
temperature to low and freeze the condensation.
When an A/C request is received by the PCM, the A/C compressor clutch will only be engaged through the A/C clutch relay if all of the following conditions are met:
The PCM does not detect excessively high or low refrigerant pressure from the A/C pressure transducer.
The PCM does not detect excessively low refrigerant pressure from the A/C cycling switch.
The PCM does not detect excessively high engine coolant temperature.
The PCM does not detect an ambient air temperature too low.
The PCM has not detected a Wide Open Throttle (WOT) condition.
Possible Causes
Fuse(s)
Wiring, terminals or connectors
A/C pressure transducer
PCM
A/C clutch relay
Electronic automatic temperature control (EATC) module
A/C cycling switch
A/C compressor clutch field coil
A/C clutch air gap
PINPOINT TEST K: THE AIR CONDITIONING (A/C) IS INOPERATIVE
NOTE:
Before carrying out the following test, diagnose any PCM or instrument cluster DTCs.
NOTE:
Before carrying out the following test, check that the A/C system pressure is above 290 kPa (42 psi). If the pressure is below 290 kPa (42 psi), refer to
Fluorescent Dye Leak
Detection
in this section.
WARNING: The heater core inlet hose will become too hot to handle and can cause
serious burns if the system is working correctly.
Allow the engine to reach normal operating temperature.
Feel the heater core inlet hose.
Is the heater core inlet hose too hot to handle?
GO to
J4
.
No
GO to
Section 303-03
to check the cooling system function.
J4 CHECK THE HEATER CORE OUTLET HOSE FOR HOT WATER
WARNING: The heater core outlet hose will become too hot to handle and can
cause serious burns if the system is working correctly.
Allow the engine to reach normal operating temperature.
Feel the heater core outlet hose.
Is the heater core outlet hose cool or cold?
Yes
CARRY OUT the Heater Core Component Test. REFER to Heater Core
under Component Tests in this section to determine whether a plugged or
partial plugged condition exists.
No
GO to Pinpoint Test A
.
Test Step
Result / Action to Take
Page 30 of 45
2006 Town Car Workshop Manual
12/30/2011
http://www.fordtechservice.dealerconnection.com/pubs/content/~WS6G/~MUS~LEN/19/...
