does anyone know the location of the mode door actuator ?
Has anyone expierenced a problem with the HVAC modes changing ??
I have no codes set, and the rest of the functions are working properly.

 

Hi, the location of the mode door is deep in the dash. If the problem you are having is that the air blows out of all the vents and can't be controlled by the control head, the most likely culprit is a vacuum problem. There are many threads on this subject. Basically the modes are controlled by vacuum. The main vacuum line starts at the back of the intake manifold, where it connects to a 90 degree nipple,(very hard to see), the line then travels through the wiring harnes across tha firewall to the vacuum tank and check valve,(under the battery box on the passenger side), from there it goes into the car to a junction block behind the glove box, and then to the control head, which sends it back to the mode actuator. Most find either that the line has come disconnected from the nipple on the manifold, or that battery acid has eaten it up near the vacuum tank, from a leaking battery. If it is the leaking battery, you need to fix the line, and also scrupously clean up the entire area with a baking soda solution and then rinse it well being careful to not get water into the computer and electric parts in that area, the frame may need to be repainted as well.
Search for vacuum line, or acid damage to get more info.
Below is a link to a thread with great info on how to fix the problem
http://forums.corvetteforum.com/show...line+vacuum+ac

Now if the problem is with the modes changing indiscriminatly, and the vacuum lines and block are ok, the problem could be a leaking tank, or a bad control head, or the actuator. SEE BELOW for a diagnostic.
Good Luck
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Air Delivery Improper
Step
Action
Value(s)
Yes
No

DEFINITION: Air flow is not being delivered from the proper mode outlet which was requested by the operator.

1
Where you sent here from the HVAC System Check?
--
Go to Step 2
Go to HVAC System Check

2
Remove the I/P RH lower insulator. Refer to Closeout/Insulator Panel Replacement - Instrument Panel (I/P) Lower in Instrument Panel, Gauges and Console.
Disconnect the I/P harness vacuum connector from the HVAC module violet vacuum (source) line.
Connect a vacuum gauge to the I/P harness vacuum line.
Start the engine and allow the engine to idle.
Measure the vacuum at the I/P harness (engine source) vacuum line.
Is the vacuum reading within the specified value?
69-117 kPa (10-17 in Hg)
Go to Step 3
Go to Step 4

3
Turn OFF the engine.
Inspect the vacuum reading at the I/P harness (engine source) vacuum line.
Does the vacuum reading hold steady?
--
Go to Step 11
Go to Step 6

4
Remove the RH front wheelhouse filler panel. Refer to Wheelhouse Filler Replacement in Body Front End.
Disconnect the engine harness vacuum connector from the vacuum tank check valve.
Connect a vacuum gauge to the engine harness vacuum (source) line.
Start the engine and allow the engine to idle.
Measure the vacuum at the engine harness vacuum (source) line.
Is the vacuum reading within the specified value?
69-117 kPa (10-17 in Hg)
Go to Step 6
Go to Step 5

5
Repair the leak or restriction in the engine harness vacuum (source) line.

Is the repair complete?
--
Go to Step 20
--

6
Connect a vacuum gauge to the vehicle interior end of the I/P harness vacuum line.
Remove the RH front wheelhouse filler panel.
Disconnect the I/P harness vacuum connector from the vacuum tank check valve.
Connect a hand vacuum pump to the vehicle exterior end of the I/P harness vacuum line.
Apply 103-108 kPa (15-20 inches) of vacuum to the line.
Measure the vacuum on the vacuum gauge inside the vehicle.
Is the vacuum reading the same as the amount of vacuum applied and does the vacuum reading hold steady?
--
Go to Step 8
Go to Step 7

7
Repair the leak or restriction in the I/P harness vacuum (engine source) line.

Is the repair complete?
--
Go to Step 20
--

8
Disconnect the vacuum tank check valve from the vacuum tank.
Connect a hand vacuum pump to the vacuum tank.
Apply 103-108 kPa (15-20 inches) of vacuum to the vacuum tank.
Does the vacuum reading hold steady?
--
Go to Step 9
Go to Step 10

9
Replace the vacuum tank check valve.

Is the repair complete?
--
Go to Step 20
--

10
Replace the vacuum tank. Refer to Vacuum Tank Replacement .

Is the repair complete?
--
Go to Step 20
--

11
Remove the I/P accessory trim plate. Refer to Trim Plate Replacement - Instrument Panel (I/P) Accessory in Instrument Panel, Gauges and Console.
Remove the I/P upper trim pad. Refer to Trim Pad Replacement - Instrument Panel (I/P) Upper in Instrument Panel, Gauges and Console.
Remove the HVAC control head. Refer to Control Assembly Replacement .
Plug one of the two HVAC control head ends of the violet vacuum line and install a vacuum gauge to the other.
Connect a hand vacuum pump to the underdash end of the violet vacuum line.
Apply 103-108 kPa (15-20 inches) of vacuum to the vacuum line.
Measure the amount of vacuum on the vacuum gauge.
Switch the connection of the vacuum gauge and the plug between the two HVAC control head ends of the violet vacuum line.
Apply 103-108 kPa (15-20 inches) of vacuum to the vacuum line.
Measure the amount of vacuum on the vacuum gauge.
Is the vacuum reading the same as the amount of vacuum applied and does the vacuum reading hold steady?
--
Go to Step 13
Go to Step 12

12
Repair the leak or restriction in the HVAC module violet vacuum (source) line.

Is the repair complete?
--
Go to Step 20
--

13
Connect a hand vacuum pump to each of the remaining vacuum lines, one at a time, at the connector which attaches to the HVAC control head.
Apply 103-108 kPa (15-20 inches) of vacuum to each vacuum line.
Observe the operation of the vacuum actuator and the related valve(s) to which the vacuum line is attached.
Does each vacuum line, actuator and related valve(s) hold vacuum and operate properly?
--
Go to Step 19
Go to Step 14

14
Disconnect the vacuum line(s) from the vacuum actuator(s) which did not operate properly.
Connect a hand vacuum pump to the vacuum actuator.
Apply 103-108 kPa (15-20 inches) of vacuum to the vacuum actuator.
Observe the operation of the vacuum actuator and the related valve(s).
Does the vacuum actuator hold vacuum?
--
Go to Step 16
Go to Step 15

15
Replace the faulty vacuum actuator.

For mode valve vacuum actuator replacement, refer to Mode Actuator Replacement .
For defroster valve vacuum actuator replacement, refer to Defroster Actuator Replacement .
For air inlet valve vacuum actuator replacement, refer to Air Inlet Actuator Replacement .
Is the repair complete?
--
Go to Step 20
--

16
Is a binding condition evident, not allowing proper actuation of the related valve(s)?
--
Go to Step 17
Go to Step 18

17
Repair the binding condition.

Is the repair complete?
--
Go to Step 20
--

18
Repair the leak or restriction in the affected vacuum line.

Is the repair complete?
--
Go to Step 20
--

19
Replace the HVAC control head. Refer to Control Assembly Replacement .

Is the repair complete?
--
Go to Step 20
--

20
Install components or connectors which were removed or disconnected.

Is the action complete?
--
Go to HVAC System Check
--

 

Thanks guys !
I have repaired my vaccum line and replaced the battery.
Things are back to normal.
Thanks again.