Question about 2004 Buick Rainier
There may be a couple of items to look at here.... but the most common problem is a source of vacumn to the pneumatic operation of the heat/a/c vent doors....if vacumn is not distributed properly to the vents you command it is assumed that there is either no vacumn to the selector swith panel(broken vac. line,kinked vac. line, defective in dash a/c control panel) or under the hood a defective vac./heater control valve that is stuck,frozen, not allowing the vacumn to pass through it to supply the indash pneumatic controls and/or panel.
Most vacumn systems that i have ever came in contact with incorporate a vacumn supply tank(nothing more then a round plastic vac. resevoir) which is used in sequence with the a/c heater controls, its purpose is to keep an even vacumn supply to all command points continously while the vehicle is being driven, without this supply one will experience the a/c coming from various different non selected dash vents upon acceleration, this is a direct relation to the tank either being defective(leaking vacumn) or its supply hose(usually vey tiny rubber/plastic tubes) being pinched or broken not allowing the vacumn to the supply tank.
listen for vacumn leaks(hissing sound), look for the obvious...broken vacumn lines or hoses, also check for a defective one way vacumn valve on some pneumatic controlled door vent systems(these valves are inserted in a vacumn line one side being the ""in" port and the other side of it being the "out" flow port,typically if these dont work the vents will also devert your a/c or heat all different ways through your dash.
to check these valves, simply remove from the vacumn hose, and apply vacumn to one side,if vacumn flows through the valve, apply the same vacumn to the opposite side of the plastic valve, if vacumn flows through on the opposite side the valve is bad, it should only allow flow from one side not the other. These valves are small and are usually white or black plastic and look like the old vacumn dash pots used on the old carbureated engines only smaller with one small hose in and one small hose out.
Posted on May 20, 2010
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Posted on Jan 02, 2017
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