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HOMESERVICE MANUALSBUICK1996ROADMASTER BASEREPAIR AND DIAGNOSIS (SINGLE PAGE)HEATING, VENTILATION & A/C (HVAC)HVAC CONTROL SYSTEMSHVAC SYSTEM - MANUALTROUBLE SHOOTINGAIR FLOWS FROM WRONG OUTLETS
1996 Buick Roadmaster Base

Air Flows From Wrong Outlets

1996 Buick Roadmaster BaseSECTION Air Flows From Wrong Outlets
  1. Turn ignition switch to RUN position. Using voltmeter, backprobe and measure voltage at vacuum/electric solenoid connector terminal No. 6 (Brown wire). If battery voltage is present, go to next step. If battery voltage is not present, repair open or short ground in Brown wire.
  2. Turn ignition off. Disconnect vacuum/electric solenoid connector. Using ohmmeter, measure resistance between vacuum/electric solenoid terminal No. 6 (Brown wire) and vacuum/electric solenoid terminals No. 1 (Light Green/Black wire), 2 (Red wire), 3 (Purple wire), 4 (Tan wire), and 5 (Light Blue wire). If resistance is 70-120 ohms for all terminals, go to next step. If resistance is not 70-120 ohms for all terminals, check vacuum/electric solenoid connections. If connections are okay, replace vacuum/electric solenoid.
  3. Connect vacuum/electric solenoid connector. Set ignition to RUN position. Turn A/C-heater control panel off. Using voltmeter connected to battery voltage, backprobe and measure voltage at vacuum/electric solenoid terminals No. 1 (Light Green/Black wire), 2 (Red wire), 3 (Purple wire), 4 (Tan wire), and 5 (Light Blue wire). If battery voltage is present at terminal No. 4 and zero volts is present at terminals No. 1, 2, 3 and 5, go to step 5). If voltage is not as specified, go to next step.
  4. Check Tan wire for open or short to battery voltage. Check for short to ground in Light Green/Black wire, Red wire, Purple wire, and Light Blue wire circuits. Check A/C-heater control panel connections. If circuits and connections are okay, replace A/C-heater control panel.
  5. Check for short to ground in Tan wire. If circuit is okay, set A/C-heater control panel to RECIRC position. Using voltmeter connected to battery voltage, backprobe and measure voltage at vacuum/electric solenoid terminals No. 1 (Light Green/Black wire), 2 (Red wire), 3 (Purple wire), 4 (Tan wire), and 5 (Light Blue wire). If battery voltage is present at terminals No. 2 and 3 and zero volts is present at terminals No. 1, 4 and 5, go to step 7). If voltage is not as specified, go to next step.
  6. Check for open or short to battery voltage on Red wire and Purple wire circuits. Check for short to ground in Light Green/Black wire, Tan wire and Light Blue wire circuits. Check A/C-heater control panel connections. If circuits and connections are okay, replace A/C-heater control panel.
  7. Check for short to ground in Red wire and Purple wires. If circuit is okay, set A/C-heater control panel to MIDDLE position. Using voltmeter connected to battery voltage, backprobe and measure voltage at vacuum/electric solenoid terminals No. 1 (Light Green/Black wire), 2 (Red wire), 3 (Purple wire), 4 (Tan wire), and 5 (Light Blue wire). If battery voltage is present at terminal No. 3 and zero volts is present at terminals No. 1, 2, 4 and 5, go to step 9). If voltage is not as specified, go to next step.
  8. Check for open or short to battery voltage in Purple wire. Check connections at A/C-heater control panel. If circuit and connections are okay, replace A/C-heater control panel.
  9. Set A/C-heater control panel to BLEND position. Using voltmeter connected to battery voltage, backprobe and measure voltage at vacuum/electric solenoid terminals No. 1 (Light Green/Black wire), 2 (Red wire), 3 (Purple wire), 4 (Tan wire), and 5 (Light Blue wire). If battery voltage is present at terminal No. 5 and zero volts is present at terminals No. 1, 2, 3, and 4, go to step 11). If voltage is not as specified, go to next step.
  10. Check for open or short to battery voltage in Light Blue wire. Check connections at A/C-heater control panel. If circuit and connections are okay, replace A/C-heater control panel.
  11. Set A/C-heater control panel to FLOOR position. Using voltmeter connected to battery voltage, backprobe and measure voltage at vacuum/electric solenoid terminals No. 1 (Light Green/Black wire), 2 (Red wire), 3 (Purple wire), 4 (Tan wire), and 5 (Light Blue wire). If battery voltage is present at terminals No. 4 and 5, and zero volts is present at terminals No. 1, 2, and 3, go to step 13). If voltage is not as specified, go to next step.
  12. Check for open or short to battery voltage in Tan wire and Light Blue wire circuits. Check connections at A/C-heater control panel. If circuits and connections are okay, replace A/C-heater control panel.
  13. Set A/C-heater control panel to DEFOG position. Using voltmeter connected to battery voltage, backprobe and measure voltage at vacuum/electric solenoid terminals No. 1 (Light Green/Black wire), 2 (Red wire), 3 (Purple wire), 4 (Tan wire), and 5 (Light Blue wire). If battery voltage is present at terminal No. 4 and zero volts is present at terminals No. 1, 2, 3 and 5, go to step 15). If voltage is not as specified, go to next step.
  14. Check for open or short to battery voltage in Tan wire. Check connections at A/C-heater control panel. If circuit and connections are okay, replace A/C-heater control panel.
  15. Set A/C-heater control panel to defrost. Using voltmeter connected to battery voltage, backprobe and measure voltage at vacuum/electric solenoid terminals No. 1 (Light Green/Black wire), 2 (Red wire), 3 (Purple wire), 4 (Tan wire), and 5 (Light Blue wire). If battery voltage is present at terminals No. 1 and 4, and zero volts is present at terminals No. 2, 3 and 5, A/C-heater control panel is okay. Go to VACUUM SYSTEM TEST  under TESTING. If voltage is not as specified, go to next step.
  16. Check for open or short to battery voltage in Light Green/Black wire and Tan wire circuits. Check connections at A/C-heater control panel. If circuits and connections are okay, replace A/C-heater control panel.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.