Chrysler 300M Service Manual page 297

LH
HEATED GLASS (Continued)
the BCM failed to complete the circuit to ground
required to energize the EBL relay coil (Fig. 3).
(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.
(Refer to 8 - ELECTRICAL/HEATED GLASS/REAR
WINDOW DEFOGGER GRID - DIAGNOSIS AND
TESTING) If there is no voltage to the rear window
defogger grid when the system is ON, (Refer to 8 -
ELECTRICAL/HEATED GLASS - DIAGNOSIS AND
TESTING - FUSE AND ELECTRICAL SHORT
TEST).
Fig. 3 REAR WINDOW DEFOGGER SYSTEM
SCHEMATIC
1 - BCM AND BUTTON LED RELAY CONTROL LINE (MANUAL
TEMPERATURE 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
DIAGNOSIS AND TESTING - FUSE AND
ELECTRICAL SHORT TEST
(1) Stop the engine.
(2) Check the fuse supplying power to the rear
glass grid relay. If the fuse is good, (Refer to 8 -
ELECTRICAL/HEATED GLASS/REAR WINDOW
DEFOGGER RELAY - DIAGNOSIS AND TESTING).
If the fuse is open, then go to Step 3.
(3) Locate the ground lug that connects the nega-
tive lead of the rear window grid to ground. Remove
the screw holding the ground lug and isolate it from
any vehicle ground.
(4) Connect one lead of an ohmmeter to the nega-
tive ground lug of the rear window grid (with the lug
still not connected to a vehicle ground), and check
the resistance to a known good vehicle ground. If the
ohmmeter indicates less than 10 ohms, then the rear
window defogger grid is shorting to the vehicle
ground, then go to Step 5. If the ohmmeter indicates
more than 100 ohms of resistance, then go to Step 6.
(5) Disconnect the rear window defogger grid volt-
age feed wire from the vehicle harness. If the ohm-
meter still indicates less than 10 ohms, then the rear
window defogger grid is shorting to the vehicle
ground and must be replaced. If the ohmmeter indi-
cates more than 100 ohms of resistance with the grid
voltage feed wire disconnected, then go to Step 6.
(6) There is a problem with the circuits that con-
nect to the rear window defogger relay. Refer to the
appropriate wiring information for circuit descrip-
tions. Check wiring with an ohmmeter to verify
proper wiring connections to the rear window defog-
ger relay. If no problems are found, then replace the
fuse and try running the system.
REAR WINDOW DEFOGGER
GRID
DIAGNOSIS AND TESTING - REAR WINDOW
DEFOGGER GRID
The horizontal grid line and vertical bus bar line is
printed and fired on the inside surface of the rear
window glass. These comprise an 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 an 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 (Fig. 4). The voltage mea-
sured should be below 1 volt. If the voltage is greater
than 1 volt then check the voltage on each grid line
at the Mid-Point with the positive lead. If the voltage
is not approximately 6 volts or half the voltage mea-
HEATED GLASS 8G - 3