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
Well Gang,
To anyone who cares, the problem has been fixed. A very long story short. It was exactly what I thought it was. A broken wire/bad contact pin, in one of the three wires that make up the J1939 Data link. It was the green one. A very strange situation if I must say so. After lots of investigation, unplugging connectors, checking resistance, continuity and general condition of all the connectors involved in the J1939 data link.
Well, with a bit of help, the engine was running and I was at the helm watching the gauges. My son was under the coach, tweaking and wiggling wires. Eventually he found the problem area. I shut down the engine and got under there with him. He pointed out the general spot. I got under there the next day and went to work on trying to find and pinpoint the exact spot. It was very tough. I eventually narrowed it down to a connector or, an inch or two in either direction of it. I ended up braking part of the connector so, I finished the job.
What I found was, a broken green wire right where it enters the back side of one of the pins. The Yellow and black one was perfect. I ruled out the thought about stress on the wire(s). If that was the case, then why didn't the yellow and black ones break also???? So, what I figured was the original installer just goofed up when stripping the green wire and cut it too deep and cut off most of the strands of the copper wire too. It took 49,000 miles to vibrate/break off the rest.
So, I cut off the entire connector and installed a Weather Pack one and all is back to normal. All my gauges work as they are supposed to. So, I hope this never happens to anyone of you, it's a severe pain in the a$$ hunt down and trace the broken section.
Scott
To anyone who cares, the problem has been fixed. A very long story short. It was exactly what I thought it was. A broken wire/bad contact pin, in one of the three wires that make up the J1939 Data link. It was the green one. A very strange situation if I must say so. After lots of investigation, unplugging connectors, checking resistance, continuity and general condition of all the connectors involved in the J1939 data link.
Well, with a bit of help, the engine was running and I was at the helm watching the gauges. My son was under the coach, tweaking and wiggling wires. Eventually he found the problem area. I shut down the engine and got under there with him. He pointed out the general spot. I got under there the next day and went to work on trying to find and pinpoint the exact spot. It was very tough. I eventually narrowed it down to a connector or, an inch or two in either direction of it. I ended up braking part of the connector so, I finished the job.
What I found was, a broken green wire right where it enters the back side of one of the pins. The Yellow and black one was perfect. I ruled out the thought about stress on the wire(s). If that was the case, then why didn't the yellow and black ones break also???? So, what I figured was the original installer just goofed up when stripping the green wire and cut it too deep and cut off most of the strands of the copper wire too. It took 49,000 miles to vibrate/break off the rest.
So, I cut off the entire connector and installed a Weather Pack one and all is back to normal. All my gauges work as they are supposed to. So, I hope this never happens to anyone of you, it's a severe pain in the a$$ hunt down and trace the broken section.
Scott
