Rear Window Defogger Inoperative. Chevrolet Blazer

For 1990-2009 cars only

Makes 🢒 Chevrolet 🢒 2005 🢒 Blazer - 2WD 🢒 Body 🢒 Doors 🢒 Rear Window Defogger Inoperative

Test Description

The number below refers to the step number on the diagnostic table.

Listen for an audible click when the RR DEFOG relay operates. Command both the ON and OFF states of the RR DEFOG relay. Repeat the commands as necessary.

Step	Action	Yes	No
Schematic Reference: Defogger Schematics Connector End View Reference: Stationary Windows Connector End Views DEFINITION: The rear window defogger is completely inoperative. No part of the rear window is heated.
1	Did you review the Rear Window Defogger system operation and perform the necessary inspections?	Go to Step 2	Go to Symptoms - Stationary Windows
2	Turn ON the ignition, with the engine OFF. Depress the rear window defogger switch. Observe the rear window defogger indicator on the HVAC Control Assembly. Does the rear window defogger indicator illuminate?	Go to Step 3	Go to Step 5
3	Connect a test lamp between the rear window defogger grid and a good ground. Does the test lamp illuminate?	Go to Step 4	Go to Step 7
4	Connect a test lamp between the left side of the rear window defogger grid and the right side of the rear window defogger grid. Does the test lamp illuminate?	Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems	Go to Step 15
5	Turn OFF the ignition. Disconnect the harness connector C5 of the HVAC Control Assembly. Turn ON the ignition, with the engine OFF. Connect a test lamp between the ignition voltage circuit of the HVAC Control Assembly and a good ground. Does the test lamp illuminate?	Go to Step 6	Go to Step 16
6	Connect a test lamp between the ignition voltage circuit of the HVAC Control Assembly and the ground circuit of the HVAC Control Assembly. Does the test lamp illuminate?	Go to Step 12	Go to Step 17
7	Command the RR DEFOG relay ON and OFF, by depressing the rear defogger switch on the HVAC Control Assembly. Do you hear a click when you command the RR DEFOG relay ON and OFF?	Go to Step 10	Go to Step 8
8	Turn OFF the ignition. Remove the RR DEFOG relay. Refer to Relay Replacement in Wiring Systems. Turn ON the ignition, with the engine OFF. Connect a test lamp between the ignition voltage circuit of the RR DEFOG relay coil and a good ground. Does the test lamp illuminate?	Go to Step 9	Go to Step 18
9	Connect a test lamp between the ignition voltage circuit of the RR DEFOG relay coil and the control circuit of the RR DEFOG relay. Depress the rear window defogger switch. Does the test lamp illuminate?	Go to Step 14	Go to Step 12
10	Turn OFF the ignition. Remove the RR DEFOG relay. Refer to Relay Replacement in Wiring Systems. Connect a test lamp between the battery positive voltage circuit of the RR DEFOG relay switched input and a good ground. Does the test lamp illuminate?	Go to Step 11	Go to Step 19
11	Connect a 30 amp fused jumper wire between the battery positive voltage circuit of the RR DEFOG relay switched input and the relay switched output to the supply voltage circuit of the rear window defogger grid. Connect a test lamp between the rear window defogger grid and a good ground. Does the test lamp illuminate?	Go to Step 14	Go to Step 20
12	Test the control circuit of the RR DEFOG relay for an open or short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?	Go to Step 23	Go to Step 13
13	Inspect for a poor connection at the harness connector of the HVAC Control Assembly. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?	Go to Step 23	Go to Step 21
14	Inspect for a poor connection at the RR DEFOG relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?	Go to Step 23	Go to Step 22
15	Repair an open or high resistance in the ground circuit of the rear window defogger grid. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair?	Go to Step 23	--
16	Repair an open or short to ground in the ignition voltage circuit of the HVAC Control Assembly. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair?	Go to Step 23	--
17	Repair an open or high resistance in the ground circuit of the HVAC Control Assembly. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair?	Go to Step 23	--
18	Repair an open or high resistance in the ignition voltage circuit of the RR DEFOG relay coil. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair?	Go to Step 23	--
19	Repair an open or high resistance in the battery positive voltage circuit of the RR DEFOG relay switched input. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair?	Go to Step 23	--
20	Repair an open or short to ground in the supply voltage circuit of the rear window defogger grid. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair?	Go to Step 23	--
21	Replace the HVAC Control Assembly. Refer to Heater and Air Conditioning Control Replacement in HVAC Systems - Manual. Did you complete the replacement?	Go to Step 23	--
22	Replace the RR DEFOG relay. Refer to Relay Replacement in Wiring Systems. Did you complete the replacement?	Go to Step 23	--
23	Operate the system in order to verify the repair. Did you correct the condition?	System OK	Go to Step 2