GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

1

Did you review the HVAC system operation and perform the necessary inspections?

--

Go to Step 2

Go to Symptoms

2

Verify that the blower motor high speed is inoperative.

Does the blower motor operate normally?

--

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 3

3

  1. Disconnect the blower motor relay.
  2. Connect a test lamp between CKT 52 (ORN) wire and ground at the relay.
  3. Turn the ignition switch to the ON position.
  4. Turn the ignition switch to the OFF position.
  5. Turn the mode selector switch to HEAT.
  6. Turn the blower switch to HIGH.

Does the test lamp light?

--

Go to Step 7

Go to Step 4

4

Connect a test lamp between CKT 52 (ORN) wire cavity A at the heater and the air conditioning (A/C) controller connector C3 and ground.

Does the test lamp light?

--

Go to Step 5

Go to Step 6

5

Repair the open in CKT 52 (ORN) wire.

Is the repair complete?

--

Go to Step 16

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6

Replace the heater and the A/C controller. Refer to Control Assembly Replacement .

Is the replacement complete?

--

Go to Step 16

--

7

Connect a self-powered test lamp between CKT 850 (BLK) wire at the blower motor relay and ground.

Does the test lamp light?

--

Go to Step 9

Go to Step 8

8

Repair the open in CKT 850 (BLK) wire between the blower motor relay and S108.

Is the wire repair complete?

--

Go to Step 16

--

9

Connect a test lamp between CKT 540 (ORN) wire and ground.

Does the test lamp light?

--

Go to Step 10

Go to Step 11

10

Replace the blower motor relay.

Is the blower motor replacement complete?

--

Go to Step 16

--

11

Inspect the HVAC fuse in the underhood fuse block.

Is the fuse open?

--

Go to Step 13

Go to Step 12

12

Repair the open in CKT 540 (ORN) wire.

Is the repair complete?

--

Go to Step 16

--

13

  1. Turn the ignition to the OFF position.
  2. Connect a self-powered test lamp between CKT 540 (ORN) wire at the blower motor relay and ground.

Does the test lamp light?

--

Go to Step 14

Go to Step 15

14

  1. Repair the short to ground in CKT 540 (ORN) wire.
  2. Replace the fuse.

Is the repair complete?

--

Go to Step 16

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15

  1. Repair the intermittent short to ground in CKT 540 (ORN) wire.
  2. Replace the fuse.

Is the repair complete?

--

Go to Step 16

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16

Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 3