GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Oldsmobile 🢒 1998 🢒 LSS 🢒 Body and Accessories 🢒 Stationary Windows 🢒 Rear Window Defogger Inoperative

Step

Action

Value(s)

Yes

No

1
  1. Turn the ignition to the RUN position.
  2. Disconnect the rear defogger relay.
  3. Connect a test lamp between relay terminal 86 and ground. Refer to Troubleshooting with a Test Lamp in Wiring Systems.

Does the test lamp light?

--

Go to Step 2

Go to Step 9

2

Connect a test lamp between relay terminal 30 and ground. Refer to Troubleshooting with a Test Lamp in Wiring Systems.

Does the test lamp light?

--

Go to Step 3

Go to Step 10

3

Connect a test lamp between terminal 30 and terminal 87 of the relay. Refer to Troubleshooting with a Test Lamp in Wiring Systems.

Does the test lamp light?

--

Go to Step 11

Go to Step 4

4
  1. Disconnect the rear defogger positive and negative feed bus connector.
  2. Connect a jumper between terminal 30 and terminal 87 of the relay. Refer to Using Fused Jumper Wires in Wiring Systems
  3. Connect a test lamp between the positive feed bus connector and the ground. Refer to Troubleshooting with a Test Lamp in Wiring Systems.

Does the test lamp light?

--

Go to Step 5

Go to Step 7

5

Connect a test lamp between the positive feed bus connector terminal A and the negative feed bus connector terminal A. Refer to Troubleshooting with a Test Lamp in Wiring Systems.

Does the test lamp light?

--

Go to Step 8

Go to Step 6

6
  1. Inspect CKT 1250 (BLK) for an open.
  2. Inspect connector C340 for proper contact.
  3. Repair the open, as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

System OK

--

7
  1. Inspect CKT 293 (PPL) for an open.
  2. Repair the open, as necessary.

Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

System OK

--

8
  1. Inspect the rear defogger connectors for proper contact.
  2. Repair the contact, as necessary. Refer to Intermittents and Poor Connections in HVAC.

Did you find and correct the condition?

--

System OK

--

9
  1. Inspect CKT 1141 (BRN) for an open.
  2. Repair the open, as necessary.

Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

System OK

--

10
  1. Inspect CKT 1140 (ORN) for an open.
  2. Repair the open, as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

System OK

--

11
  1. Connect a test lamp between terminal 86 and terminal 85. Refer to Troubleshooting with a Test Lamp in Wiring Systems.
  2. Turn the rear defogger ON.

Does the test lamp light?

--

Go to Step 15

Go to Step 12

12
  1. Connect the rear defogger relay.
  2. Disconnect the connector to the heater and A/C programmer.
  3. Connect a test lamp between terminal A (C61 and C67), terminal D5 (C68), or F5 (CJ2) and ground. Refer to Troubleshooting with a Test Lamp in Wiring Systems.

Does the test lamp light?

--

Go to Step 13

Go to Step 17

13
  1. Inspect the heater and A/C programmer for the proper terminal contact.
  2. Repair the contact, as necessary.

Refer to Intermittents and Poor Connections in HVAC.

Did you find and correct the condition?

--

System OK

Go to Step 14

14

Replace the heater and A/C programmer. Refer to Programmer Replacement

Did you find and correct the condition?

--

System OK

--

15
  1. Inspect the terminals at the rear defogger relay.
  2. Repair the terminals, as necessary.

Did you find and correct the condition?

--

System OK

Go to Step 16

16

Replace the rear defogger relay.

Did you find and correct the condition?

--

System OK

--

17
  1. Inspect CKT 193 (WHT) for an open.
  2. Repair the open, as necessary.

Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

System OK

--