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Dan, Auto Service Technician
Category: Car
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Experience:  GM ASEP A.A.S. 14 years GM experience. Mark of Excellence and Professional Guild awarded.
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2000 Olds Bravada: climate control..defrost to heat, but i..heater box

Resolved Question:

I have a 2000 Olds Bravada with climate control. the climate controls have been replaced because i could not switch from defrost to heat, but i still have no heat. the heater box is hot so i know the heat is there. Im sure the vacume acuaters are operating because i can see them working as i switch the controls. i could use a little heat as the weather has changed considerably. is ther an acuater that i can see or has one of the temperature sensors failed. the heat doesnot work in manual made oviously. thank you mike keezer.
Submitted: 6 years ago.
Category: Car
Expert:  Dan replied 6 years ago.
Subject:Repeat HVAC Actuator Replacements - keywords door cool heat mode temperature #PIT4427 - (06/15/2007)

 

Models:2003-2007 HUMMER H2, SUT
1999-2007 Chevrolet Silverado Classic
1999 -2007 GMC Serria Classic
2002-2006 Cadillac Escalade, ESV, EXT
2000-2006 Chevrolet Avalanche, Suburban, Tahoe
2000-2006 GMC Yukon, Yukon Denali, Yukon XL, Yukon Denali XL
2002-2007 Chevrolet Trailblazer Models
2002-2007 GMC Envoy Models
2004-2007 Buick Rainier
2005-2007 Saab 9-7X
1998-2004 Chevrolet S/T Classic Blazer and S10 Pickup
1998-2004 GMC S/T Classic Jimmy and Sonoma
1998-2007 Oldsmobile Bravada
2003-2006 Chevrolet SSR

 



This PI Being Updated To Add Additional Model Years. Please Discard PI02080.


The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern:

A replacement HVAC actuators is inoperative or that has worked one time and quit. The HVAC control head learns the stopping points based on how far the HVAC DOOR travels. If the actuator reachs the mechanical stops on the back of the actuator it will be outside of the range that the HVAC control head can learn. If the actuator was not mounted to the HVAC case prior to plugging in its connector, the actuator will go out of range and be inoperative.

Recommendation/Instructions:

Always attach the HVAC actuator to the case before installing the electrical connector.

If an actuator is out of range it may be possible to bring it back into range by following the procedure below:

  1. Turn ON the ignition, with the engine OFF.
  2. Connect a 3 amp fused jumper wire between the actuator control circuit and the 5 volt reference circuit of the actuator connector.
  3. Remove the jumper wire and actuator connector when the actuator is at the center position.
  4. If the actuator doesn't move in step 2. Try installing the jumper wire from control circuit and the ground circuit of the actuator.
  5. With the actuator in the center position, install the actuator to the hvac case and secure the mounting screws and then connect the actuator connector.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.


 

Heating Insufficient

Step

Action

Value(s)

Yes

No

1

Did you perform the Diagnostic System Check?

--

Go to Step 2

Go to Diagnostic System Check

2

Verify that the heating is insufficient.

Is the heating sufficient?

--

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

Go to Step 3

3

Inspect for the following conditions:

A leak in the cooling system
A low coolant level
A loose belt or a worn belt
A leaking heater hose or a kinked heater hose
The loss of the radiator cap pressure seal

Does the malfunction still exist?

--

Go to Step 4

Go to Step 29

4

  1. Adjust the heater controls to the following modes:
    - The HEATER mode
    - The blower speed control to the HI position
    - The full WARM mode
  2. With the ignition switch in the ON position, inspect the airflow out of the floor air outlet.
  3. Inspect the outlet attachment.

Is the airflow high?

--

Go to Step 5

Go to Step 8

5

Does the airflow change with different blower speeds?

--

Go to Step 6

Go to Step 12

6

Perform the System Performance Test. Refer to System Performance Test

Is the heater output temperature correct?

--

Go to Step 7

Go to Step 13

7

  1. Inspect the following areas of the vehicle for cold air leaks:
    - At the cowl
    - In the heater case
    - In the vents
  2. Correct any conditions as necessary.

Is the repair complete?

--

Go to Step 29

--

8

Perform the function test. Refer to System Performance Test

Is the repair complete?

--

Go to Step 29

Go to Step 9

9

Check the airflow from the vent outlets.

Is the airflow from the vent outlets high?

--

Go to Step 10

Go to Step 18

10

Move the defroster and/or the vent valve to the HEATER mode.

Is the defroster airflow correct?

--

Go to Step 11

Go to Step 19

11

  1. Remove the floor air outlet. Refer to Air Outlet Replacement - Floor.
  2. Inspect the outlet for any obstructions.
  3. Change the blower speeds.

Does the airflow change with different blower speeds?

--

Go to Step 10

Go to Step 12

12

  1. Inspect the following parts:
    - The motor blower switch
    - The blower motor resistor assembly
    - The blower motor wiring harness
  2. Repair any conditions as necessary.
  3. Perform the heater output temperature check. Refer to System Performance Test

Is the heater output temperature correct?

--

Go to Step 7

Go to Step 13

13

  1. Turn the temperature rotary knob to full HOT.
  2. Inspect the temperature cable indexing.

Is the temperature valve fully closed?

--

Go to Step 14

Go to Step 23

14

  1. With the temperature valve in the full WARM position, start the vehicle.
  2. Inspect the air temperature around the heater inlet and the heater outlet hoses.

Is the air temperature around both hoses at least at the specified value?

24°C (85°F)

Go to Step 15

Go to Step 24

15

  1. Remove the hoses at the heater core.
  2. Inspect the hoses for proper installation.

Were the hoses properly installed?

--

Go to Step 16

Go to Step 26

16

  1. Backflush the heater core.
  2. Drain and replace the coolant.
  3. Start the vehicle.
  4. Inspect the air temperature around both hoses.

Is the air temperature around both hoses at least at the specified value?

24°C (85°F)

Go to Step 17

Go to Step 24

17

Replace the heater core. Refer to Heater Core Replacement in Heater and Ventilation -- Non-A/C.

Is the repair complete?

--

Go to Step 29

--

18

  1. Turn the mode knob to the DEFROST mode.
  2. Inspect the airflow.

Is the defroster airflow not present or low?

--

Go to Step 19

Go to Step 11

19

Does the airflow change with different blower speeds?

--

Go to Step 20

Go to Step 12

20

Inspect for airflow obstructions at the blower inlet and plenum.

Did you find and correct a condition?

--

Go to Step 29

Go to Step 21

21

  1. With the blower in the HI mode, turn the temperature rotary knob from the full HOT position to the full COLD position.
  2. Listen for a change in the airflow.

Is a change in the airflow audible?

--

Go to Step 22

Go to Step 27

22

Check for an airflow obstruction between the blower and the system outlets.

Is the repair complete?

--

Go to Step 29

--

23

  1. Re-index the cable.
  2. Inspect the temperature valve adjustment, cables and linkage.

Did you find and correct a condition?

--

Go to Step 29

--

24

Check the thermostat for proper installation and seating.

Is the thermostat properly installed and seated?

--

Go to Step 28

Go to Step 25

25

Reinstall the thermostat.

Is the repair complete?

--

Go to Step 14

--

26

Properly reinstall the hoses.

Is the repair complete?

--

Go to Step 14

--

27

Inspect the following components:

The temperature valve
The control assembly
The blower motor wiring harness

Is the repair complete?

--

Go to Step 29

--

28

Replace the thermostat.

Is the repair complete?

--

Go to Step 29

--

29

Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 3


Dan, Auto Service Technician
Category: Car
Satisfied Customers: 3490
Experience: GM ASEP A.A.S. 14 years GM experience. Mark of Excellence and Professional Guild awarded.
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