How not to add switches

Go directly to: switch locations to consider
cluster-switch-front

I see many questions in the forums regarding the switches in the lower left dash panel, known as the cluster switch panel. Seeing so many empty spots (up to 5 depending on the options purchased), and having a need to add a switch or two for some accessory they’re adding to the vehicle, they probably think they can substitute a switch in place of a blank spot, and voila – hook up some wires and they’re done.  Actually, a few years ago this was a nice alternative, as the switches were all independent of each other, but that isn’t the case in very recent vehicles where switches are communicating* to their master computer modules via one wire, rather than simple power-on or power-off, and this switch assembly, and the switches in your steering wheel, are good examples of that.

As shown in my edited diagram below from Mazda’s service manual (to show how all 6 switches can be accommodated), the switches for DSC, TPMS Set, BSM, LDWS and potentially two others all control a resistor array so that via one wire, the Instrument Cluster knows the selections of all 6 switches (when and which option has been chosen), and from there communicates to other appropriate modules controlling those functions.   Another wire for that circuit is Ground (Battery -) and another pair of wires accommodate nighttime LED back-lighting for the switch labels.

So unless your able to communicate with the cluster module, adding a BSM switch for example, without actually having that option, would maybe activate the BSM lamp in your Instrument Cluster, but you wouldn’t be able to do much else.  On the other hand, if you were able to create a new module and that communicates with the cluster module, then adding switches to this panel could be very fruitful.  You wouldn’t even have to add a switch, as you could just “listen” for a long push of the DSC button (as opposed to a momentary push, as an example) and use that signal to toggle your own option(s).  A Russian entrepreneur has done just that by developing a module that controls an add-on front camera for Mazda 3 vehicles and listens for the option control signals as the cluster module is talking across the CAN network to the Dynamic Stability Control module.

*    When these momentary-on switches are pressed, they change the input voltage on the wire connected to the instrument cluster. There is a set “resting” voltage but when a switch is pressed, the voltage changes as it is going through one or more resistor(s) before going to the instrument cluster.   In the case of the DSC switch, which takes priority as it offers no resistance, the voltage is dropped to zero.

cluster-switch

Here’s a photo of the rear of the cluster switch assembly to confirm the 4 connection harness pins I’ve described and that you would gain nothing by adding any switches without creating a module and doing some programming as well.

cluster-switch-rear


Switch locations to consider

⇓    Two options to consider:

  • Rocker switch similar to what is used for the footwell illumination option.  If you don’t have that option, that area  above the hood release is a nice location for an option switch you might be considering.
  • In Europe, Canada and some other regions, where the trunk release isn’t offered, that location too, is another switch location to consider.

footwell light switch

⇓    Another switch that might be easier to adapt for other purposes is the one designed for the MX-5 Retractable Fastback (RF) option; a dedicated 2-way switch with momentary-on contacts, while being pushed up or down.  It is unknown at this time whether the switch can be added to the air bag message panel assembly, or if the entire assembly would have to be replaced, but either way this option sounds expensive.

2017-mazda-mx-5-rf-switch

rf-button1

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