Nighthawk AC1900 C7000v2 Downstream Channel Indicator Light Blinking with slow speeds

[dan333]

I am having issues with my Netgear Nighthawk AC1900 WIFI Cable Modem Router, Model C7000V2. It is about 5 months old. It was working fine for the last four months. Over a month ago, the indicator light that shows if downstream channel is locked is blinking green, which signifies downstream channel is not locked. Xfinity tells me I have strong signal. My Xfinity plan is 100 Mbps, wirless and wired connection speeds vary from 3-5 Mbps or 20-30 Mbps. Sometimes, the downstream indicator light stays solid green, but most of time is blinking. I have tried resetting it multiple times. I called Xfinity and they said no issue with lines and signal is strong. Can someone please tell me how I can troubleshoot this. I don't want to pay 90$ for a 6 month Netgear support contract if it something I can fix with help from the community. Thanks for your help. 

[plemans · Accepted solution]

If you've checked all the cables/connectors to ensure you're good, then the ISP needs to check the line as you have power issues (out of spec) and a bunch of errors

[plemans]

A screen snip of your cable connections page and event logs help us check your signal. Xfinity's first response is always "the line is fine". 

Start with removing any amplifiers, signal attenuators, or splitters from the coax.
From there check the line for kinks, damage, moisture in the line.
Check the connectors for improperly made ends, foil touching the copper coax line, bad/old/cheap connectors, or corroded connections. Replace them if you do.
If you can, simply connect the modem right where the coax comes into the home. This prevents wiring in the home from being the issue. And some ISP’s charge if the wiring issue is in the home. So this helps prevent this.

[dan333]

Cable connection screenshot:

[plemans]

You have a ton of errors in the line, your power is way out of spec, and you have non locked channels. 

Start with removing any amplifiers, signal attenuators, or splitters from the coax.
From there check the line for kinks, damage, moisture in the line.
Check the connectors for improperly made ends, foil touching the copper coax line, bad/old/cheap connectors, or corroded connections. Replace them if you do.
If you can, simply connect the modem right where the coax comes into the home. This prevents wiring in the home from being the issue. And some ISP’s charge if the wiring issue is in the home. So this helps prevent this.

If non of the above help, the isp needs to check the line. 

[dan333]

I don't have any amplifiers, signal attenuators, or splitters. No kinks, damage, or moisture in line.  No improperly made ends, foil touching the copper coax line, or bad/old/cheap connectors or corroded connections.

I connected modem where coax comes into home. When I plugged into coax cable that connects to outside of house, the download speed went up to 75 Mbps, but the indicator light flashed showing no downstream channel connection. Please see cable connection results below when modem is connected directly to coax cable coming into home from outside.

When I hooked it up back inside house, I got slower speeds, but the downstream channel locked. See screenshot below. 

[dan333]

Now after the modem being back online for about three hours, the downstream channel light is blinking again and my download speed went from 35 to 13 Mbps. See screenshot below for cable connection values. Looks like more errors and downstream channels not being locked again. 

[plemans · Accepted solution]

If you've checked all the cables/connectors to ensure you're good, then the ISP needs to check the line as you have power issues (out of spec) and a bunch of errors

[dan333]

It was a lot of work to get Xfinity to come out and check the line, but they finally agreed with the agreement that I would pay $100 if the issue was with my line or modem. The Xfinity technician who came out determined the issue was with their line. Their connection at the top of the pole had let water in causing the issue. Now that it is fixed, all downstream channels are locked, with power in spec, and with no errors, and my download speed is back up at 85 Mbps. Thank you so much for helping me trouble shoot this. I had no idea what to do, and now I am back up and running without any additional cost on my end. When I called Xfinity, they tried to tell me the issue was with my modem and that I needed to call the modem manufacturer or that I needed to rent a modem from them. Based on your help, I was confident on what the issue was, and I actually got it resolved. 

[plemans]

Glad that fixed it!

It is a pain with xfinity as I've had to go through the "we'll charge you if its on your end" battle with them before. 

I've actually had to rent a modem from them before because they still claimed it was on my end until I could prove it wasn't the netgear modem and then their modem. 

Stinks when you have to fight just to get them to ensure a good signal. 

But either way, its working again!

Happy to hear it. 

[dan333]

Thanks again for giving up your time to help someone in need. It's very much appreciated.