GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2000 🢒 Blazer - 4WD 🢒 HVAC 🢒 HVAC Systems - Manual 🢒 Temperature Control Inoperative

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 temperature control is inoperative.

Does the temperature control operate normally?

--

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

Go to Step 3

3

Inspect the HVAC I fuse 21.

Is the fuse open?

--

Go to Step 21

Go to Step 4

4
  1. Disconnect the air temperature valve sensor.
  2. Turn the ignition switch to the RUN position.
  3. Move the headlamp switch to the PARK position.
  4. Using the J 35616-A , connect a J 39200 Digital Multimeter (DMM) between cavity 8 (CKT 733) of the air temperature valve motor connector and ground.
  5. Move the temperature control knob from the HOT position to the COLD position.

Does the voltage vary smoothly and continuously within the specified range?

0-12 V

Go to Step 5

Go to Step 10

5

Using the J 35616-A , connect a J 39200 DMM between cavity 10 (CKT 341) of the air temperature valve motor connector and ground.

Does the voltage equal the specified value?

B+

Go to Step 6

Go to Step 8

6

Using the J 35616-A , connect a J 39200 DMM between cavity 10 (CKT 341) and cavity 7 (CKT 1850) of the air temperature valve motor connector.

Does the voltage equal the specified value?

B+

Go to Step 7

Go to Step 9

7

Replace the air temperature valve motor. Refer to Temperature Actuator Replacement .

Is the repair complete?

--

Go to Step 26

--

8

Locate and repair the open or high resistance in CKT 341 between the IP fuse block HVAC I fuse 21 and air temperature valve motor.

Is the repair complete?

--

Go to Step 26

--

9

Locate and repair the open or high resistance in CKT 1850 between the air temperature valve motor and G200.

Is the repair complete?

--

Go to Step 26

--

10

Did the voltage remain at or near the specified value regardless of the temperature control knob position?

B+

Go to Step 11

Go to Step 16

11
  1. Disconnect the heater controller/heater and A/C controller connector C3.
  2. Using the J 39200 DMM, backprobe the jumpers at C3 terminal A (CKT 341) to terminal C (CKT 1050).
  3. Turn the ignition switch to the RUN position.
  4. Move the headlamp switch to the PARK position.
  5. Measure the voltage drop.

Does the voltage equal the specified value?

B+

Go to Step 12

Go to Step 13

12

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

Is the repair complete?

--

Go to Step 26

--

13

Move the headlamp switch to the OFF position.

Does the voltage equal the specified value?

B+

Go to Step 14

Go to Step 15

14

Locate and repair the high resistance in CKT 1050 between splice pack SP203 and G203.

Is the repair complete?

--

Go to Step 26

--

15

Locate and repair the open or high resistance in CKT 1050 between the heater controller/heater and A/C controller connector C3 terminal C and splice pack SP203.

Is the repair complete?

--

Go to Step 26

--

16

Did the voltage remain at or near the specified value regardless of the temperature control knob position?

0 V

Go to Step 17

Go to Step 11

17
  1. Disconnect the heater controller/heater and A/C controller connector C3.
  2. Using the J 35616-A , construct jumper leads in order to connect all of the connector C3 cavities to the appropriate terminals at the controller.
  3. Using the J 39200 DMM, backprobe the jumper at C3 terminal B (CKT 733) to ground.
  4. Turn the ignition switch to the RUN position.
  5. Move the headlamp switch to the PARK position.
  6. Move the temperature control knob from the HOT position to the COLD position.

Does the voltage vary smoothly and continuously within the specified range?

0-12 V

Go to Step 18

Go to Step 19

18

Repair the open or high resistance in CKT 733 between the heater controller/heater and A/C controller and the air temperature valve sensor.

Is the repair complete?

--

Go to Step 26

--

19

Using the J 39200 , backprobe at the heater controller/heater and A/C controller connector C3 terminal A and terminal C in order to measure the voltage drop.

Does the voltage equal the specified value?

B+

Go to Step 24

Go to Step 20

20

Using the J 39200 , backprobe at the heater controller/heater and A/C controller connector C3 terminal A and ground in order to measure the voltage drop.

Does the voltage equal the specified value?

B+

Go to Step 12

Go to Step 8

21

Using the J 39200 DMM, probe the HVAC I fuse 21 test points.

Does the J 39200 DMM display the specified value at both test points?

B+

Go to Step 22

Go to Step 23

22

Locate and repair the short to ground in CKT 341 between the IP fuse block and the heater controller/heater and A/C controller connector C3 terminal A.

Is the repair complete?

--

Go to Step 26

--

23

Locate and repair the open in CKT 300 between the IP fuse block and the ignition switch. Refer to Power Distribution Schematics in Wiring Systems.

Is the repair complete?

--

Go to Step 26

--

24
  1. Disconnect the jumper at the heater controller/heater and A/C controller connector C3 terminal B. Do not disconnect the jumper from the controller.
  2. Measure the voltage at terminal B of the controller at the disconnected end of the jumper.
  3. Disconnect the air temperature valve sensor.
  4. Move the temperature control from the HOT position to the COLD position.

Does the voltage vary smoothly and continuously within the specified range?

0-12 V

Go to Step 25

Go to Step 12

25

Repair the short to ground in CKT 733 between the heater controller/heater and A/C controller connector C3 terminal B and the air temperature valve sensor.

Is the repair complete?

--

Go to Step 26

--

26

Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 3