2000 Buick Century Driver-side Heater Control

My 2000 Century Custom has 2 control levers that independently adjust the air temp for driver and passenger. The driver's control lever moves freely but
the air is stuck on 'heat' full-blast no matter what the lever setting. Occasionally, when the lever is adjusted, it will change over to cool vent air (not a/c) and be stuck in that setting for a while. The passenger side control regulates just fine. Any suggestions on how to fix this?
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Is the driver's temperature control a knob or a slider?

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It is a slider.
Silver Surfer wrote:

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Can anyone help please.....
Steve C wrote:

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I've looked through the service manual for your year's model plus the year before and the year after. Cannot find any sign of a temperature control that uses two levers. Sorry.

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For what it's worth here is the diagnostic table for a 2000 Century's temperature control:
Document ID# 610218 2000 Buick Century -------------------------------------------------------------------------------- Air Temperature Control Inoperative Step Action Value(s) Yes No
1 Was the heater-A/C control Diagnostic System Check performed? -- Go to Step 2 Go to Diagnostic System Check (See procedure below this one)
2 Inspect the HVAC fuse in the fuse block.
Is the HVAC fuse open? -- Go to Step 3 Go to Step 4
3 Repair short to ground in circuit 41 (BRN). Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Is the repair complete? -- Go to Step 13 --
4 Turn the ignition switch off. Disconnect the left electric actuator electrical connector. Turn the ignition switch on. Use a digital multimeter (DMM) to measure the voltage between the left electric actuator harness connector terminal 5 and ground. Is the measured voltage within the specified range? 9-14V Go to Step 6 Go to Step 5
5 Repair the poor connection or open in circuit 41 (BRN). Refer to Testing for Intermittent and Poor Connections and Circuit Testing in Wiring Systems.
Is the repair complete? -- Go to Step 13 --
6 Use a DMM in order to measure the voltage between the left electric actuator harness connector terminal 6 and ground. Vary the driver temperature knob from full cold to full hot. Does the voltage vary within the specified range? 0.5-4.5V Go to Step 7 Go to Step 8
7 Replace the left electric actuator. Refer to Temperature Actuator Replacement (LH) .
Is the repair complete? -- Go to Step 13 --
8 Inspect for a short to ground or short to B+ in circuit 1199 (DK BLU). Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Is there a short to ground or short to B+ in circuit 1199 (DK BLU)? -- Go to Step 9 Go to Step 10
9 Locate and repair the short to ground or the short to B+ in circuit 1199 (DK BLU).
Is the repair complete? -- Go to Step 13 --
10 Inspect for a poor connection or open in circuit 1199 (DK BLU) between the heater-A/C control harness connector terminal C7 and the left electric actuator harness connector terminal 6.
Is there continuity in circuit 1199 (DK BLU)? -- Go to Step 11 Go to Step 12
11 Repair the poor connection or open in circuit 1199 (DK BLU) between the heater-A/C control harness connector terminal C7 and the left electric actuator harness connector terminal 6. Refer to Testing for Intermittent and Poor Connections and Circuit Testing in Wiring Systems.
Is the repair complete? -- Go to Step 13 --
12 Replace the heater-A/C control. Refer to Control Assembly Replacement .
Is the repair complete? -- Go to Step 13 --
13 Verify that the system operates properly.
Does the system operate properly? -- System OK Go to Diagnostic System Check
Document ID# 599174 2000 Buick Century -------------------------------------------------------------------------------- Diagnostic System Check Test Description The number(s) below refer to the step number(s) on the diagnostic table.
Lack of communication may be due to a partial or total malfunction of the class 2 serial data circuit. The specified procedure will determine the particular condition.
The presence of DTCs which begin with "U" indicate some of the modules are not communicating.
Step Action Yes No
1 Install a scan tool.
Does the scan tool power up? Go to Step 2 Go to Scan Tool Does Not Power Up in Data Link Communications
2 Turn ON the ignition, with the engine OFF. Attempt to establish communication with the BCM and PCM control module(s). Does the scan tool communicate with the control module(s)? Go to Step 3 Go to Scan Tool Does Not Communicate with Class 2 Device in Data Link Communications
3 Select the control module display DTCs function on the scan tool.
Does the scan tool display any DTCs? Go to Step 4 Go to Symptoms
4 Does the scan tool display any DTCs which begin with a "U"? Go to Diagnostic Trouble Code (DTC) List/Type in Data Link Communications Go to Step 5
5 Does the scan tool display DTC B1000? Go to Diagnostic Trouble Code (DTC) List/Type in Body Control System Go to Step 6
6 Does the scan tool display the PCM DTCs P0530 or P1546? Go to Diagnostic Trouble Code (DTC) List/Type in Engine Controls - 3.1L engine or Diagnostic Trouble Code (DTC) List/Type in Engine Controls - 3.8L Go to DTC Table

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try pulling the hvac fuse for 30 min to reset the temp door accuators
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