Chassis Multiplex - What is it - How does it work - What coaches have it

[Frank McElroy]

Lately I've seen a lot of questions both on the forum and in personal emails asking about chassis multiplex systems.  In the files, I just posted an article that should help explain the system and why Monaco converted from conventional wiring to a multiplex system as had manufacturers of most cars made in the past 20+ years.

Starting with 2008 Signature, then by mid 2008 model year production, all Executive and Dynasty coaches transitioned from conventional chassis wiring systems to multiplex systems.

Late 2021, I spoke with Ames Jacoby (Roadmaster Manager on the project).  Unfortunately, the main Monaco person who worked with Kongsberg for the CCM programming and Eaton for the switch module programming is no longer with us.  The CCM modules and the switch modules were sold to Monaco pre-programmed.  These parts are now obsolete and only available from salvage yards.  Both Kongsberg and Eaton no longer have the capability to manufacture replacements or even reprogram existing modules.

here is a link to the article now in our files was published by Monaco in their December/January 2007/08 edition of Lifestyles Magazine.

Multiplex systems can be very complicated and a bit hard for folks to understand.  Most folks understand direct wiring between a switch and a device but not multiplex wiring.

My best way to explain multiplex wiring is to think about it as a desktop computer.  The keyboard is just like the dash switches and the computer interacts with your display screen, printer, modem, etc.

So, in a Monaco chassis multiplex system just like any other multiplex system, each dash switch sends a unique digital signal to a Chassis Control Module called a CCM.  There are actually 2 CCM modules.  The reason for this is that there are so many outputs you needed 2.  In addition to the digital switch inputs, you also have analog voltage inputs from the smart wheel keypads  The CCM basically replaced the SmartWheel control module.

Now for outputs from the CCM.  These are on multiple levels.  Anything related to the engine like cruise control or Jake brake are sent over the J1939 databus.  This same databus ties the engine, transmission, ABS, and dash gauge cluster communications together on just 2 data wires.

All the rest of the outputs from the CCM are done with individual wires either directly or through relays.  These include anything you can imagine.  Lights, wipers, AC condenser fan, generator controls you name it.  For rear lights, the signal is sent down a digital databus to a control board in the BBR which then turns on rear lighting (brake, signal, etc).

I hope this sheds some light on the wiring mystery of a chassis multiplex coach.

[Brett63]

And when one part fails, you can absolutely screw yourself into the ground looking for repair help....lol 

You left out the Vorad module. Shame on you Frank....lol

[Frank McElroy]

17 hours ago, Brett63 said:

And when one part fails, you can absolutely screw yourself into the ground looking for repair help....lol 

You left out the Vorad module. Shame on you Frank....lol

Brett, yep your right, the Vorad computer is also on the J1939 databus.  That is a nice collision avoidance system.  I wish my coach had it.

[Frank McElroy]

Since this topic was first posted, there have been a number of developments including an option to repair failed dash switch modules on a Kongsberg Chassis multiplex system and a 5 volt aux power supply to fix most SmartWheel problems.  Here is a link to an extensive 12 page thread.