Pinpoint Test N: The Defrost System Will Not Shut Off Automatically — ON At All Times
Normal Operation
Under normal operation, the heated backlight relay receives power from the central junction box through circuit 185 (BK). When the rear window defrost switch is depressed on the climate
control assembly, a ground signal is sent to the instrument cluster module (ICM) through circuit 688 (GY/LB). When the ICM receives ground through circuit 688 (GY/LB), the ICM grounds
circuit 1009 (OG/YE) to activate the heated backlight relay. Power is then sent to the rear window defrost grid through circuit 186 (BN/LB) from the heated backlight relay. The rear window
defrost grid is grounded to the chassis through circuit 1205 (BK).
Possible Causes
Inoperative ICM.
Inoperative heated backlight relay.
Short to voltage in circuit 186 (BN/LB).
Short to ground in circuit 688 (GY/LB) or 1009 (OG/YE).
Inoperative DATC or manual climate control assembly.
Disconnect: ICM C220a.
Disconnect: Function Selector Switch C294b (Manual A/C Only) or DATC Module C228a.
If equipped with manual A/C, measure the resistance between function selector switch C294b-12, circuit 688
(GY/LB) harness side and ICM C220a-15, circuit 688 (GY/LB) harness side.
If equipped with DATC, measure the resistance between DATC module C228a-12, circuit 688 (GY/LB) harness
side and ICM C220a-15, circuit 688 (GY/LB) harness side.
Is the resistance less than 5 ohms?
Yes
If equipped with manual A/C, GO to M8.
If equipped with DATC, INSTALL a new DATC climate
control assembly. REFER to Section 412-00.
No
REPAIR the circuit. TEST the system for normal
operation.
M8 CHECK CIRCUIT 1205 (BK) FOR AN OPEN
Measure the resistance between function selector switch C294b-6, circuit 1205 (BK) harness side and ground.
Is the resistance less than 5 ohms?
Yes
INSTALL a new manual climate control assembly.
REFER to Section 412-00.
No
REPAIR the circuit. TEST the system for normal
operation.
M9 CHECK CIRCUIT 1009 (OG/YE) FOR AN OPEN
Disconnect: ICM C220a.
Measure the resistance between ICM C220a-4, circuit 1009 (OG/YE) and rear window defrost relay socket pin 86,
circuit 1009 (OG/YE) harness side.
Is the resistance less than 5 ohms?
Yes
INSTALL a new ICM. REFER to Section 413-00. TEST
the system for normal operation.
No
REPAIR the circuit. TEST the system for normal
operation.
2003 Explorer/Mountaineer Workshop Manual
http://www.fordtechservice.dealerconnection.com/pubs/content/~WS3N/~MUS~LEN/19/S
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