Rear Window Defogger Malfunction
Diagnostic Instructions
Diagnostic Fault Information
Circuit
|
Short to Ground
|
Open/High Resistance
|
Short to Voltage
|
Signal Performance
|
Rear Window Defogger Relay Switch B+
|
1
|
1
|
-
|
-
|
HVAC Control
|
U1510 00
|
U1510 00
|
U1510 00
|
-
|
Rear Window Defogger Relay Control
|
B0283 02
|
B0283 05
|
B0283 05
|
-
|
Rear Window Defogger Grid Control
|
1
|
1
|
2
|
-
|
Rear Window Defogger Relay Coil Ground
|
-
|
1
|
1
|
-
|
Rear Window Defogger Grid Ground
|
-
|
1
|
1
|
-
|
1. Rear Defogger Inoperative
2. Rear Defogger Always ON
|
|
|
Circuit/System Description
When the HVAC control module receives a rear window defog
request from the HVAC control faceplate, the HVAC control module
will supply voltage to the relay coil. Battery positive voltage is
supplied at all times to the relay switched input and the relay
coil is always grounded. When the relay is energized, current from
the relay switched input will to flow through the switch contacts
and out the relay switched output to the rear window defogger
grid.
Diagnostic Aids
The rear window defogger indicator will still function when the
rear defogger switch is pressed, but any of the following
conditions may cause the rear window defogger grid not to
function:
• |
The battery state of charge is
out of range causing the HVAC control module to suspend the rear
window defogger operation. |
• |
The remote start enable
ambient temperature is greater than 5°C (40°F).
|
Reference Information
Schematic Reference
Defogger Schematics
Connector End View Reference
Component Connector End Views
Description and Operation
Rear Window Defogger Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
1. |
Engine running, observe the
scan tool instrument cluster Rear Defogger Switch parameter while
pressing the E18 Rear Defogger Grid switch in the HVAC
control. |
⇒ |
If the value is always Inactive or always Active,
replace the K33 HVAC Control Module. |
2. |
Command the Illuminate All
Indicators ON and OFF with a scan tool. The defog indicator should
turn ON or OFF while changing between the commanded states.
|
⇒ |
If the defog indicator is always ON or always OFF,
replace the K33 HVAC Control Module. |
3. |
Command the E18 Rear Defogger
Grid ON and OFF with a scan tool, the E18 Rear Defogger Grid should
turn ON or OFF while changing between the commanded states.
|
Circuit/System Testing
1. |
Ignition OFF, disconnect the
KR5 Rear Defogger Relay. |
2. |
Test for less than 5 Ω
between the ground circuit terminal 2 and ground. |
⇒ |
If greater than the specified range, test the
ground circuit for an open/high resistance. |
3. |
Engine running, verify a test
lamp does not illuminate between the control circuit terminal 5 and
ground. |
⇒ |
If the test lamp illuminates, test the control
circuit for a short to voltage. |
4. |
Verify a test lamp illuminates
between the B+ circuit terminal 3 and ground |
⇒ |
If the test lamp does not illuminate, test the B+
circuit for a short to ground or an open/high resistance. |
5. |
Ignition OFF, disconnect the
X2 harness connector at the E18 Rear Defogger Grid. |
6. |
Test for less than 5 Ω
between the ground circuit terminal 1 and ground |
⇒ |
If greater than the specified range, test the
ground circuit for an open/high resistance. |
7. |
Connect the X2 harness
connector at the E18 Rear Defogger Grid. |
8. |
Connect a 40 A fused jumper
wire between the B+ circuit terminal 3 and the control circuit
terminal 5 of the KR5 Rear Defogger Relay. Verify the E18 Rear
Defogger Grid is activated. |
⇒ |
If the E18 Rear Defogger Grid does not activate
and the circuit fuse is good, test the control circuit for an
open/high resistance. If the circuit tests normal, test or replace
the E18 Rear Defogger Grid. |
⇒ |
If the E18 Rear Defogger Grid does not activate
and the circuit fuse is open, test the control circuit for a short
to ground. If the circuit tests normal, test or replace the E18
Rear Defogger Grid. |
9. |
Connect a test lamp between
the control circuit terminal 1 and the ground circuit terminal
2. |
10. |
Engine running, command the
E18 Rear Defogger Grid ON and OFF with a scan tool, the test lamp
should turn ON and OFF when changing between the commanded
states. |
⇒ |
If the test lamp is always ON, test the control
circuit for a short to voltage. If the circuit tests normal,
replace the K33 HVAC Control Module. |
⇒ |
If the test lamp is always OFF, test the control
circuit for a short to ground or an open/high resistance. If the
circuit tests normal, replace the K33 HVAC Control Module. |
11. |
If all circuits test normal,
test or replace the KR5 Rear Defogger Relay . |
Component Testing
Rear Window Defogger Grid Test
1. |
Engine running, turn on the
E18 Rear Defogger Grid. |
2. |
Verify that a test lamp
illuminates between each E18 Rear Defogger Grid line and ground.
The test lamp should be off when testing at the ground side of the
grid and get brighter as the test lamp moves closer to the voltage
supply side of the grid. The test lamp should be dim when testing
each grid line in the middle. |
⇒ |
If the test lamp remains bright at the middle of
the grid line, test for an open between the test point and the
ground side of the grid. |
⇒ |
If the test lamp remains off at the middle of the
grid line, test for an open between the test point and the voltage
side of the grid. |
Relay Test
1. |
Ignition OFF, disconnect the
KR5 Rear Defogger Relay. |
2. |
Test for 60-180 Ω
between terminals 1 and 2. |
⇒ |
If the resistance is not within the specified
range, replace the KR5 Rear Defogger Relay. |
3. |
Test for infinite resistance
between the following terminals: |
⇒ |
If not the specified value, replace the KR5 Rear
Defogger Relay. |
4. |
Install a 5 A fused jumper
wire between relay terminal 2 and 12 V. Install a jumper wire
between relay terminal 1 and ground. Test for less than 2 Ω
between terminals 3 and 5. |
⇒ |
If greater than the specified range, replace the
KR5 Rear Defogger Relay. |
Repair Instructions
Perform the
Diagnostic Repair Verification after completing the diagnostic
procedure.
|