Chrysler 2000 LHS, Руководство пользователя, Страница: 431 / 1591

DIAGNOSIS AND TESTING
SERVICE PROCEDURES
Electrically Heated Rear Window Defogger opera-
tion can be easily checked in three steps:
(1) Use ATC, Manual Heater-A/C self diagnostics,
or the DRB III
t
scan tool to check fault codes and
control button operation. Note, this does not check
the EBL system. There are no fault codes that can
check for the EBL grid, relay, or wiring. Refer to
steps 2 and 3 for system test.
(2) Perform system test with voltmeter.
(3) Check voltages at rear grid relay and refer to
Rear Widow Defogger Relay Test table.
A/C-HEATER AND ATC CONTROL HEAD
Refer to Group 24, Heating and Air Conditioning
for instructions on how to use the DRB III
t
scan tool
or the control head self-diagnostics to test the control
head. The problem is not with the control head if no
trouble codes are found. The next step should be to
check the rest of the system after the A/C-Heater or
ATC control head is checked.
SYSTEM TEST
(1) Start engine. With the engine running, push
the Rear Window Defogger button on the ATC or
Manual A/C Heater Control Head. The button LED
indicator should light. If the EBL indicator does not
light on the MANUAL-A/C HEATER CONTROL,
then there may be a wiring problem. This may also
indicate that the BCM will not complete the circuit
to ground that is required to energize the EBL relay
coil (non-ATC vehicles only). Refer to EBL Relay
Test. On ATC vehicles, the LED indicator may light
when the BCM failed to complete the circuit to
ground required to energize the EBL relay coil.
(2) Using a DC voltmeter with a 0-15 volt range,
connect the negative lead to a known good vehicle
electrical ground.
(3) Touch the positive bus bar and check voltage.
The voltage should be above 11 volts. Push the Rear
Window Defogger button to turn off the indicator.
The measured voltage should be 0 volts. If these volt-
ages are correct then the problem is with the Rear
Window Grid or Grid ground electrical connection. Go
to the Grid Lines test to check the Grid and ground
connection.. If there is no voltage to the rear window
defogger grid when the system is ON, then go to the
Fuse and Electrical Short Test.
GRID TEST
The horizontal grid line and vertical bus bar line is
printed and fired on the inside surface of the rear
window glass. These comprise and electrical circuit.
The electrically conductive lines are composed of a
silver ceramic material which when fired on glass
becomes bonded to the glass and is highly resistant
to abrasion. It is possible, however, that a break may
occur in and individual grid line resulting in no cur-
rent flow through the line. To detect breaks in grid
lines, the following procedure is required:
(1) Stop the engine. Connect the negative lead of a
0-25 volt range voltmeter to a known good vehicle
electrical ground.
(2) Start the engine and push the rear window
defogger button to turn on the system.
(3) Touch the ground side (point B) of the Rear
Window Defogger Grid. The voltage measured should
be below 1 volt. If the voltage is greater than 1 volt
then check the voltage on each grid line at the Mid-
Fig. 1 Rear Window Defogger System Schematic
1 – BCM AND BUTTON LED RELAY CONTROL LINE (A/C-
MANUAL CONTROL ONLY)
2 – VEHICLE VOLTAGE SUPPLY
3 – GROUND CONNECTOR
4 – REAR WINDOW GRID LINE STRUCTURE
5 – POINT B
6 – MIDPOINT C (TYPICAL)
7 – POINT A
8 – POWER CONNECTOR
Fig. 2 ATC Control Head
8N - 2 ELECTRICALLY HEATED SYSTEMS
LH
DESCRIPTION AND OPERATION (Continued)