Who knows about FCCC "MMDC" and its issues?

dougmac wrote:
I am not following the acronyms ... but it sounds like you are talking about your electronic dash/info center. It sounds like the dash has lost its data connection to the chassis J1939 data link. If you can locate the connection where the data cable connects, the resistance between the two wires coming from the chassis should be around 60 ohms.

dougmac,
In essence, you're correct. I've talked with Freightliner on this and that's one explanation of the problem but, the other is the MMDC is possibly bad. Incedentally, the "MMDC" is the Multiple Module Data Computer. The "Medallion" information center is the receiving end of the MMDC and displays what the MMDC tells it to. My "Trip-Tek" is an option from Itasca/Winne that is an auxiliary way of observing engine ops, i.e. oil pressure, odometer(s), turbo boost, and many other instruments. And it shows all of it on the monitor of the Sony rear view/back up camera. So, in our rig, and I suppose many others out there, we have a redundancy of displays of engine info.

1, the gauges themselves
2, the Medallion Info Center
3, the Trip-Tek info system on the rear view camera monitor

all displaying much of the same thing. And yes, after talking with the service writer at a Freightliner Service Center in El Paso TX, he agrees that it's most likely a bad connection of the data link (J1939)to the MMDC. But, the MMDC is a runner up in this problem. So, we'll see. At this present time, I've got the MMDC off and in my hand. But, I have no idea what the "data link-J1939) looks like and how to check it. I was sent a trouble shooting schematic and guide but, so much of it is way over my head. Talk about Acronyms, wow, that document is full of them. Whew!
Scott

John Wayne,
Boy, you're close on this one I think. You see, I had an issue with the Annunciator panel and gauges a while ago. Long story short, A call to Freightliner and a nice lady talked me through some checks on that "10" pin connector on the back of the MMDC and, through her guidance, I found I had lost the grounds to that system. Now, not knowing where the grounds come from, I figure a ground is a ground, so, I made my own, "Tee-d" into the ground wires on the back of that 10 pin connector and YAHOOOOOOOOOO, it all started working again. Buzzers, gauges, annunciator panel, and all, went back to normal operation.

So, could this just be a bad ground, quite possibly but, where to check is the question. And, according to the trouble shooting schematic and guide that Freightliner sent me, You got to be real careful on your checking of certain wires or you could "Poof" some gauges!
Scott

Executive,
Yes Sir, that's one of the first things I checked prior to making the decision to drive this rig farther after I had this issue develop. I got out my little trusty volt/ohm meter and checked ALL the battery voltage. That's the chassis and house batteries while the engine was running. All were over 13 volts. Around 13.2 on the chassis and around 13.3 or so on the house batteries. So, that gave me the "go-a-head" to drive this thing to a nicer town. So, I'm pretty sure it's not the alternator. Thanks for the suggestion.
Scott

And thanks for all the help here.