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The first step checks a disconnected hose at the switch all the way to the vacuum motor in order to test door operation. The second does a function test of the actual switch for proper sequencing of vacuum.
1) Check the A/C-Heater function selector switch. It may be the switch itself, hoses plugged, kinked or more than one motor jammed/broke. There are six ports on the back. No. 3 is your vacuum source and No. 4 is unused. Apply vacuum to 2,5 and 6. You should hear a door move. No. 2 and 5 are connected to the same motor so you will have to plug one and test the other. If you have a "T" I would plug 2 and 5 in and pull a vacuum on both at the same time. By checking both together you can reach full throw on the door. This motor splits the air between the floor and upper vent/defrost when you choose a blend function. No. 1 is your air inlet / recirc door, you can check that if you want.
2) Go to the run (engine can remain off as long as you mind the battery draw and it will be quieter to hear door movement) position to get vacuum the pump running. Give it a chance to draw down the reservoir. Put the selector knob in the off position and remove a hose one at a time and listen for suction, check 1,2,3,5 and 6. The only one that should not have vacuum is No. 6. Select MAX A/C should have vacuum at 1, 3 and 6 only. Select A/C or Vent, uses same ports, should have a vacuum at 3 and 6 only. Select Vent/Floor should have vacuum at 2,3 and 6 only. Select Floor should have vacuum at 2,3 and 5 only. Select Floor/Defrost should have vacuum at 2 and 3 only. Select Defrost should have vacuum at 3 only.
Last edited by lug; 06-07-2012 at 11:17 AM.