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MULTIPLEX MASTERY:

 

Replacing your Vansco SRM





If you have an MCI coach with Vansco multiplexing, there may come the day when you need to replace one of your solid-state relay modules — SRMs, for short. SRMs can roughly be thought of as the brains of the multiplex electrical system. And like operating on a brain, it's imperative that you know what you're doing — because one slip-up can cause a real headache.

Simply put, there are two versions of the SRMs.

  • The T07-3057 arrives without programming and will "learn" from the other SRMs in the coach
  • The T07-3057PRO comes pre-programmed with updated information the system needs and has to "teach" the other modules

The "Learning" and "Teaching" process requires specific steps to be taken, but care needs to be used, especially during the T07-3057PRO installation, lest the technician accidentally wipe out the programming.

This article addresses the installation of both parts. The T07-3057PRO is used in coaches with VINs from 62032 to 63630. The T07-3057 is used in all D coaches and E/J coaches with VIN number 63631 and up. Coaches within the VIN range of 62032 to 63630 were originally released from the factory with SRMs that contained V3 application software. Replacement modules purchased from MCI Service Parts are not compatible with V3 application software; therefore this SRM requires specific installation instructions.

  • E/J coaches 62032-63630 = T07-3057PRO
  • E/J coaches 63631 and up = T07-3057
  • All D coaches = T07-3057

NOTE:

  • When installing T07-3057PRO, this SRM is actually re-programming the original good modules on the coach (but only one at a time).

  • When installing T07-3057, the original good modules on the coach will reprogram the new module being installed.

T07-3057PRO INSTALLATION



NOTE: REMOVE AND REPLACE ONLYONE SRM AT A TIME.

If more than one SRM is replaced at a time, the new SRM may not program the SRMs correctly. If the #1 module is being replaced, start by disconnecting the #2 module to program the parcel rack module. If #2 module is being replaced, start by disconnecting #1 module to program the parcel rack module. If the parcel rack module is being replaced, start by disconnecting #1 module to program #2 module first. After the new module has reprogrammed one module, repeat the programming steps with the battery master-disconnect to reprogram the remaining module.

  1. Make certain that the coach you are working on is in the VIN range of 62032 to 63630 and that you have purchased SRM T07-3057PRO.

  2. Open the passenger entrance door.

  3. Turn off the bus power using the main battery disconnect switch (knife switch), located in the battery compartment.

  4. Open the J-Box with T-handle inside the coach by the driver window or the latch release under the J-Box door.

  5. Locate the SRMs in the front junction box as shown in Figure 1.

  6. Figure 1: Location of J-Box SRMs
  7. Remove the failed SRM.

    1. Disconnect the square harness plugs from the failed SRM by depressing the tab on top of the plugs to disengage the locking mechanism as shown in Figure 2.
      Note: If the connector tab is missing, remove the connector by sliding a screwdriver underneath the lock tab.

    2. Figure 2: How to remove connectors
    3. Disconnect the circular harness connector by turning the collar counter-clockwise 90°.

  8. Install the new SRM.

    • Connect the harness plugs to the SRM.
      Note: An audible click should be heard, ensuring that the square connectors are properly fastened. When connecting the round connector, a slight click will be felt when the locking ring is locked in place.

  9. Unplug the "B" connector from the left-hand side of the good SRM in the front junction box. Refer to Figure 1.
    Note: The goal in disconnecting the “B” connector on the other module is to achieve a scenario where the new module you are installing is only talking to one other module in the coach—not two modules. This is a requirement for the programming to succeed.

  10. Move the ignition switch to the RUN position.

  11. Turn the main battery-disconnect switch to the ON position and wait 3 minutes.
    Warning: DO NOT turn the ignition switch OFF before the three-minute timeline, as interruption of the programming sequence will render the SRM inoperative.

  12. Turn the main battery disconnect switch to the OFF position. Wait 10-15 seconds.

  13. Turn the main battery disconnect switch to the ON position again and wait 3 minutes.

  14. Turn the main battery disconnect switch to the OFF position.

The replacement module has now re-programmed the module in the rear parcel rack, which should be the only module it was communicating with since the other module in the front J-Box was disconnected.

Now reconnect the "B" connector on the other module in the front J-Box. Repeat steps 10-13, which will re-program the remaining module. After completing step 13, all three modules should be fully functional, and the application software should be updated to version 4.3.

T07-3057 INSTALLATION



Battery master disconnect switch without toggle switch



  1. Open entrance door.
  2. Turn battery master disconnect switch OFF.
  3. Turn the ignition switch to Run position.
  4. Replace the defective SRM(one at a time). You cannot have more defective modules than good ones.
  5. Turn battery disconnect switch to ON for 3 minutes ( it takes approximately 2 minutes for the SRMs to program, and any interruption of the programming may render the SRM in-effective).
  6. Turn the battery master disconnect switch OFF for 10 seconds.
  7. Turn the battery master disconnect switch ON again for 3 minutes. Power LED should be solid and Net LED should be flashing on the new module.
  8. Turn the battery master disconnect switch OFF.
  9. Turn the ignition OFF.
  10. You are done.

Battery master disconnect switch with toggle switch (MDS System)



Many E4500 and J4500 coaches were equipped with an electronic main disconnect switch (MDS) system, and the reprogramming procedure is slightly different than the procedure above. Compare your coach with Figure 3 below to determine which is the correct programming procedure for your coach.

Figure 3: MDS Disconnect System, 2007-2010 E4500 and J4500 coaches
  1. Open entrance door.
  2. Press toggle switch OFF(you should hear relays clicking off).
  3. Turn battery master disconnect switch OFF.
  4. Turn the ignition switch to Run position.
  5. Replace the defective SRM(one at a time).
  6. Turn the battery master disconnect switch ON for three minutes.
  7. Press and hold the toggle switch OFF for 10 seconds and release.
  8. Wait 3 minutes again.
  9. Press and hold the toggle switch OFF for 10 seconds and release.
  10. If Power LED is solid and Net LED is flashing, you are done.
  11. If not, repeat steps 6-9.

If in doubt, call MCI Technical Support at 800-241-2947. One of MCI's tech experts should be able to further explain the process or even walk you through steps.

The FYI from MCI editorial staff values your feedback. Please e-mail any suggestions, comments, or ideas for future articles to fyi@mcicoach.com.

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