D Sedan Entrance Door Controls (Pneumatics)

In Section 3, Entrance Door Controls - D Series Sedan Style, the electrical portion of the sedan door was discussed. In this tip, the pneumatic portion of the circuit will be discussed.

The entrance door cylinder is actually two cylinders in one, with the LH side separate from the RH side. The pistons inside the cylinders are connected together by the main shaft. The LH side has 2 airlines connected to it, and the RH side has two lines containing anti-freeze/water solution in it. See Figure 1. (The blue collar on the drawing represents the separation between the 2 halves of the cylinder.)

Figure 1

The air pressure that flows through lines 2 & 3 causes the entrance door to open and close. Air pressure on line 2 opens the door, and on line 3 closes the door.

The RH half of the cylinder is filled with an anti-freeze/water solution. As the door opens or closes, this solution flows through lines 4 & 5 transferring from one side of the piston to the other. This fluid transfer acts as a speed regulator so the entrance door opens and closes slowly and smoothly. See Figure 2.

Figure 2

There is an additional component in this circuit. Lines 4 & 5 connect to a valve located on the control panel in the spare tire compartment. This valve is called the door stop control valve, and its function is to stop the flow of the anti-freeze solution between lines 4 & 5. See Figure 3.

Figure 3

When the Skinner Valve on the control panel is energized, air pressure is applied to the control port of the door stop control valve. This closes the valve, stopping the flow of anti-freeze and stopping the movement of the entrance door. When the Skinner Valve is de-energized, air pressure on the control port is exhausted and the anti-freeze is allowed to flow again and the door is able to move.

If the anti-freeze level becomes low in the air cylinder, creating an air pocket, the dampening feature will be lessened, allowing the entrance door to "slam" open or closed.

If you need further assistance, contact the MCI Customer Support Center at (800) 241-2947.

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