Who knows about FCCC "MMDC" and its issues?
Gents, I've searched and read many issues regarding the old "VDC" units and the newer MMDC units. I'm thinking I may have developed an MMDC issue. Here's the scenario. We're presently on vacation and...
Forum Discussion
The J1939 data link is the network that allows controllers from different manufacturers to all communicate with each other.
The communication travels over a twisted pair of wires that connect all of the controllers together. (the wires are usually green and yellow) At each end of these wires there is a 120 ohm resistor. Here is a drawing I drew of how the network would be typically wired.
Because there is a 120 ohm resistor at each end of the backbone, there should be 60 ohms of resistance between the yellow and green wires at any point on the circuit.
You said there is a 10 pin connector. If you wanted to check to see if the unit was connected to the J1939 data link, make sure all of the controllers are powered down then identify the pins in the connector for the data link and check the resistance value between the two pins. If it is around 60 ohms, you are connected to the data link.
The communication travels over a twisted pair of wires that connect all of the controllers together. (the wires are usually green and yellow) At each end of these wires there is a 120 ohm resistor. Here is a drawing I drew of how the network would be typically wired.
Because there is a 120 ohm resistor at each end of the backbone, there should be 60 ohms of resistance between the yellow and green wires at any point on the circuit.
You said there is a 10 pin connector. If you wanted to check to see if the unit was connected to the J1939 data link, make sure all of the controllers are powered down then identify the pins in the connector for the data link and check the resistance value between the two pins. If it is around 60 ohms, you are connected to the data link.
