With all the sophisticated design and technological advances of the E4500 and J4500 coaches, most of us don't give much thought to one of their most simple, generally dependable systems — the entrance door. At least not until something goes wrong.
Over the years, MCI has made a few changes to the entrance door system for the E and J models. In 2003, MCI switched to a multiplexed electrical system, giving operators built-in test lights to aid diagnostics. A new door control module followed soon after. However, the basic function of opening and closing the door and locks remains the same. This month, we want to take a few moments to review the function, operation, and components of the E/J coach entrance door.
The sedan-style entrance door control module is a pneumatically controlled, electrically operated mechanism. It contains electrical solenoids that control airflow to the valves, which then distribute the air to the door and lock cylinders. The switches and the lock relay control these solenoids. The door system also contains a manual override should any problems occur in the air circuits of the door control.
Starting with the door closed and locked, opening and closing the entrance door is as simple as pushing and holding a switch, at least to the driver. When either the interior or exterior door-open switch is depressed, the locks must be disengaged before the door can actually swing open. This is done by removing power from the door-lock solenoid, allowing the air to be released from the lock cylinders. Removing this electrical power also explains why the door does not lock until the master switch is in the “on” position, supplying power to the lock solenoid.
Once the locks retract, the door is free to be swung open by applying controlled air pressure to the "open" side of the door cylinder (figure 2). The door cylinder is a double acting cylinder, in that it can be driven in either direction, open or closed, by air pressure. A single double-sided piston rides inside of the smooth bore of the cylinder. As air is applied to the open side of the cylinder, the piston is forced outward, extending the length of the cylinder and opening the door on its hinges. At the same time, the previously used "close" air is released to exhaust from the cylinder. If this old air is not able to exhaust, the opening action compresses the trapped air and prevents the cylinder from extending its full length.
Closing the door is exactly the opposite, with the added effect of locking the door once closed. Pressing either "close" switch allows air into the close side of the cylinder while allowing the previous "open" air to exhaust. The cylinder rod is retracted back into the cylinder bore, pulling the door closed.
Once fully closed and the master power switch is on, the door-closed sensor in the jamb senses the door position and signals the system to apply air to the two door-lock cylinders. The lock relay, located next to the lock module, is energized to apply power to the door-lock solenoid, extending the lock cylinders.
Recent years have shown a change in basic design of the door module, even though its function has remained the same. Instead of two exhaust ports as shown in figure 1, the newest module (04-23-1090) shown in figure 3 has a single exhaust port, shared by both the open and close functions. This new module also features a new electrical connector on the solenoids that allows adaptor 04-23-1095 to connect to the wire harness of earlier E and J series coaches, one per solenoid. The design is completely different, and if the earlier style module cannot be repaired, it must be replaced with the new assembly.
|APPLICIBLE SCHEMATICS BY UNIT #||E4500||J4500|
|60000 to 62031||07-14-1041||07-14-6312|
|62032 to 64454||07-14-1280||07-14-1280|
|64455 to 64648||07-14-3026||07-14-3026|
|64648 to present||07-14-3516 as part of||07-14-3490|
E/J SERIES COACH ENTRANCE DOOR TROUBLESHOOTING
|MALFUNCTION||POSSIBLE CAUSES||CHECK FOR:|
|Locks do not extend||(1)||Door-closed switch failure||(a)||Blown fuse|
|(b)||Door-closed switch may be opened (Tip: Stepwell light stays on)|
|(2)||Faulty door lock relay||(a)
|(b)||Loose plugs and pins to relay connections|
|(3)||Latch solenoid failure||(a)||Faulty Solenoid|
|(b)||Wiring for opens or shorts to solenoid|
|(4)||No air pressure||Air system needs service|
|Locks do not retract or extended all the time||Door lock switch failure||
Shorted door-closed switch (Tip:Stepwell light stays off)
|Upper door lock (only) does not retract||Broken lock cylinder||Broken spring inside lock cylinder|
|Locks retract slowly||Air is slow to exhaust||(a)||Quick Release Valve is sticking|
|(b)||Latch solenoid is sticking|
|Door locks 'cycle' while coach is in motion or with change of defroster speed||Loose door-closed sensor||Orientation of sensor; adjust as needed|
|Door will not open or close when using interior or exterior switches||(1)||Switch failure
||Check for open or shorted switch|
|(2)||Fuse is opened||Check fuse F15 for power|
|(3)||Faulty wiring||Open or shorted wiring between switch(es) and door control module|
|(4)||Exhaust air is blocked||Dirty or restricted muffler on door module|
|(5)||No air pressure||Air system needs service|
|(6)||Over-rule is engaged||Correct position of overrule valve|
|Door closes by itself when OPEN switch is released||(1)||CLOSE switch is stuck||Interior or exterior switches are stuck in closed position|
|(2)||OPEN solenoid is stuck in exhaust mode||Air exhausting from cylinder|
|Door creeps opened slowly||Leak in door-closed air circuit||Leak in CLOSE solenoid valve|
|Door creeps closed slowly||Leak in door-opened air circuit||Leak in OPEN solenoid valve|
Still have questions on this open-and-shut issue? Ask your Fleet Support Manager or contact MCI technical support at 800-241-2947.
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