Multiplexing Ten Years Later

Peter Luhrs

In January, I presented on the status of multiplexing after ten years in service. I received some positive feedback and shared interesting stories during the week. So I thought I would put some ideas down on paper that we talked about and even some things we did not talk about.

Life Expectancy

The life of any electrical system depends on four things:

1. Installation and quality practices by the vehicle manufacturer: Well-designed electrical systems can be made to look bad when poorly installed. Average systems can look good when they are well-implemented.

2. The multiplex system: Is it well-designed? Is it rugged? Proper testing and design of the electrical system are very important. Some vehicle manufacturers install components without proof they were ever tested.

3. Service provided during the life of the vehicle: Good practices mean a longer life. Poor practices mean your electrical system may deteriorate faster.

4. Support provided by the vehicle and/or electrical system manufacturer: Good support means the technicians are less likely to implement poor practices.

The idea is to use the four topics above as a guideline to ensure you have a great electrical system for years to come. The following will review how these points may affect your next vehicle.

Installation Practices

Numerous examples of poorly installed systems, both hardwired and multiplexed, can be found in the field. It is up to you, the vehicle purchaser, to ensure that quality standards are being used when building your vehicle. Before placing a bid, take the time to examine the electrical systems from a few vehicle manufacturers. Determine if you like how they are installed. Most manufacturers will offer multiplexed systems as an option.

Be sure the manufacturer builds more than 25 multiplexed systems each year. If a manufacturer only builds five trucks per year with a system that is different than its standard electrical system, you can probably count on one or more items of the four checkpoints not being up to par.

The System Itself

Do some research on multiplex systems. Have the multiplex manufacturer provide you with a presentation on its system. Determine all available options. Different vehicle manufacturers will implement electrical systems in different ways. Make sure you ask to see all of the onboard diagnostics, service information, switch states, and troubleshooting information you can. Next, if you plan on having a display, check out how the screens are laid out. Ensure they are intuitive for your department. If you already have a vehicle with a display, go over the screen layouts to make sure you get something similar on your next truck. Ask the multiplex manufacturer for test reports for each module it supplies to the vehicle manufacturers. If you get the runaround on test data, the manufacturer is probably not performing proper tests and you can check item two off the list as not being met.

Maintenance and Service

When you finally do get your vehicle, make sure you maintain it properly. If it is multiplexed, you can obtain information in one of three ways:

1. Onboard service information-if the vehicle has a display, it can likely have information about the vehicle including switch states.

2. Connect a computer with diagnostics software and extract or view the vehicle configuration.

3. Contact the vehicle manufacturer. Since the vehicle was configured with a computer program, it will have it on file and can easily print you a new configuration report.

If both hardwired and multiplex systems are designed well and installed properly, how do they stand up? We checked with a few ambulance remounters and found that they are replacing entire electrical systems more often when they are hardwired vs. multiplexed. We have even found that a few remounters started replacing hardwired systems with multiplex systems because each time they remounted a multiplexed truck they spent little or no time on electrical system updates or repairs.

Multiplex systems, after several years in service, have consistently been found to be very similar to their original manufactured state. Hardwired systems are less likely to maintain their as-installed state. This is partially because of poor maintenance practices and larger wire bundles.

Why would someone not use a multiplex system today? Sometimes a department cannot afford it because some manufacturers charge several thousand dollars for the option. It may not make sense to your budget. I have spoken with only a few that had a bad experience with a multiplex system. Typically, these issues were years ago. In some cases, a department thought it had a bad experience with a multiplex system but it was really a switch problem or another component. Talk with your technicians. I am amazed at how often they are not consulted when it comes to making decisions on what goes into a new piece of apparatus.

Last but not least, be sure to contact the multiplex manufacturer if you are not getting the help you need.

After ten years and many lessons learned, multiplex systems have proven themselves to be a viable way to wire fire apparatus. Keep in mind the four-piece guideline, and if you spec a multiplex system on your next apparatus, you should experience few problems over the lifetime of the truck.

PETER LUHRS is the director of multiplex solutions at Weldon, a division of Akron Brass. Under his direction, the V-MUX product was brought to production.

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