I recently had a repair person to my home and he discovered a weak signal to the DVR in my living room. That explains why sometimes the picture just fades out. He told me that there was nothing wrong with the Comcast wiring and that there might be a problem with the wiring in my wall and that I should hire an electrician to investigate this. The wiring in the walls is only 12 years old and there is no reason for it be faulty. I need someone from Comcast to figure this out for us. How should I proceed?
I wonder if your issue is somewhat similar to mine in a certain way. Just like in your case, the cables in my house are 12 years old as well. I don't know your case in particular, but in my case I have a few variables to consider like the cable , a smart TV, the cable box and a wifi router. Those three devices are very close to each other, and I am suspecting magnetic interference creating some type of problem. Thus I am leaving the cable for last.
I don't know the extent of the troubleshooting the technician provided at your case, but if you are able, you should do a visual trace of that cable wherever that cable is visible (outside/attic/etc). if the cable is a high quality cable like the one used by Comcast, runs straight from the main entrace point all the way to the DVR without a coupler or splitter and is clear of any kink, sharp bend or any other damage, I would wait on getting that line replaced. On the other hand, If the cable is an unbranded low quality cable, you definitely need to replace it.
Assuming you live in a house and have easy access to the main entrance point, one way to test the line is to buy some length of a high quality coax cable (50ft) and move the DVR and a TV to a place the cable can reach. If everything works after that, it might be the line if nothing else was affecting the DVR. If it does not work and you are using a high quality test cable, it will not be the line unless everything has gone bad at once!
If someone has old cables installed in the wall, you can at least unscrew the outlet plate and check the cable connections on the back of the plate.
Using a new RG6U quad-shield cable just run through the room to your current set-up would show if the cable in the wall is the problem. If the new cable works you can just run it along the baseboards behind furniture. Most cables found inside walls were installed as the house was built.