I extended my cable line to my garage, at first it seemed all worked ok. I started having issues on just certain channels, weather channel, and some other local channels. Contacted comcast as a power failure and they reset everything but made no difference. I don't understand why some channels are fine and some aren't. I checked all connections and cables. even switched boxes around, no difference. Help
I used rg6 cable. I checked my signal strength as you suggested on my unit in the house. 34.33
the problem is on one of the smaller boxes, that remote does not have the buttons to access the diagnostics unless there is another way. I called comcast but keep getting recordings to call again later due to storms?
This could be caused by a weak signal, which can affect only certain channels. Check the connections to the cable box, especially the incoming coax, and eliminate any unnecessary splitters.
To check signal strength with a Motorola box, tune to the offending channel, turn off the box with the remote, then within two seconds hit "OK/Select." This will bring up the diagnostics screen. Select "Inband Status" (probably page d04) and look for "SNR" for the tuner(s). This value should be in the mid to upper 30s. You may be able to improve the signal strength by adding a signal amplifier to the incoming cable line.
It also may be a weak signal caused by problems outside your house, in which case a call to 1-800-COMCAST to have them send out a tech to check on it may be of benefit.