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Mitsubishi AC Interface Issue



  • Anton Johnsson

    Hi Justin,

    I want to preface this by saying that I don't have a lot of cases on this specific unit so my experience is a bit limited.

    However, by the description, this sounds like some sort of buffer full issue considering that it occurs some time after boot. Is the L6 light blinking constantly until everything stops working? Since L6 blinking indicates that there's traffic on the BACnet line, if it's constantly blinking then maybe there is some kind of overload.

    Another theory is if a setting in the AC prevents communication after a certain time. A Mitsubishi technician could probably answer this.

    You mentioned that you've tried with another Intesis unit of the same type so hardware issues on the Intesis are at least ruled out. It could still be an issue on the BACnet line or in the BACnet system. Since it was used for an MS/TP connection previously, are there any artifacts left from this connection in the BMS?

    You could also try resetting the Intesis device to see if that solves anything. This procedure is not commonly used so the method is not very user friendly but it's possible this way:

    Using Tera Term to perform Factory Reset.
    After installing the software we need to configure it.
    1.-Choose correct com Port

    2.-SETUP -> Terminal ->
    New-Line -> Receive = Auto and Transmit = CR+LF. Check Local echo.

    3.-SETUP -> Serial ->
    Flow control = Xon/Xoff and close with click on "New setting".

    4.-Enter Comm. In Terminal.
    Info? = Info about the device connected.
    defaultcfg = Factory reset

    At this point the device has been reset and the default IP is

    These are just the notes I can think of on top of my head. Let me know your thoughts and progress on this.

  • Justin Miller

    I went back and while the gateway is sending BACnet data, the L6 LED flashes at about the same rate as the Ethernet port LED, but not at an extreme rate. When it stops sending BACnet data, the Ethernet port LED will still show activity, but the L6 LED will stay solid on.

    I'm assuming I'll need a USB cable to use the Tera Term software. I didn't have one that would work on hand. I did try the Restore Settings option in the Web UI, but it didn't fix the issue as the gateway was only sending data for about 5 minutes.

    One other thing I noticed is that when looking at other gateways of the same model we have installed elsewhere, they seem to have a later firmware (Firmware, Application Software Version Those are using BACnet MS/TP, but they do not have this problem with BACnet communication. It's a long shot, but I'm wondering if the one I am having issues with would need a firmware update.

  • Anton Johnsson

    Yeah, the LED behavior sounds normal so I wouldn't worry about that. And yes you do need to connect over USB for the reset method.

    I will create a ticket in our support portal from this thread as we can't post files directly to the forum (it's a security measure) and there is a newer FW file that we can try with.


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