Thermal Issues With Home Internet Gateway/Router as a Cause of Dropped/Slow Internet or Wi-Fi Connection

Userlevel 2

I am a Newbie here and a fairly new T-Mobile Home Internet customer. But my background is electrical engineering and I've been around a while. Like many community members I have experienced frustrating degradation of my internet connectivity after a period of operation, which is temporarily fixed by cycling the Gateway's power (otherwise known as a soft reset, not the paperclip nuclear option). The standard fix per T-Mobile Tech Support is to just perform that reset, which isn't a “fix” at all. Though many others have noted the thermal connection, I feel it’s time we get organized on this.


Without going into great detail and after surfing a number of forum threads and through my own direct experience, I have become convinced that the primary cause of the various complaints expressed by posters is heat buildup in the Gateway's enclosure and a subsequent compromise in performance in one or several of the Gateways numerous devices. There could be multiple devices affected, manifesting in different failure modes, but one primary cause – heat.


What I'm asking community members to do is to test this theory by keeping a record of the time from device reset (powering down, then back up) to failure or degradation of either internet or wi-fi connectivity or any other failure mode, and then to apply some means of enhanced airflow through the Gateway's enclosure, whether it be placing a muffin fan on top of the Gateway (blowing up, not down) or simply sitting the Gateway atop an A/C vent in your home with constant airflow and recording any difference in the time between reset and the failure. Repeating this sequence several times and then posting your results here, on this thread, will be most helpful.


If, as I strongly suspect will be the case, a correlation between enhanced airflow and increased “up-time” is documented in one place (here) by multiple forum members, we will have a powerful tool to get T-Mobile's management to fix this problem. Please don’t post here unless you have performed the requested action; there are many other threads to use.


What do you say?

34 replies


I have now not had a loss of internet since June 10th.  The fan solved the problem so far.  

The 5G cylinder sits in the exact same place as it did during the many May failures.  It is just raised about 1 inch by sitting it on top of the USB fan. I made no other changes to the setup, not even rotating the 5g cylinder.  

I went from seemingly random failures to none.

I recently added t-mobile’s YouTube TV offer and no problems.   I was concerned it wouldn’t show local channels with the home internet jumping around, but the location is determined by your cellphone. Very pleased so far.  

I now have gone over two months without a reset since adding the fan below the unit.  Plus my usage has gone up as we now have YouTube TV in use regularly.  I get 80 to 120 down and 20 to 50 uploads.  One thing I forgot to report is that I have the WiFi turned off.  I go out the Ethernet port to an eero mesh system to supply WiFi coverage in my house. 

It is obvious to me there is a heat problem at a minimum in the design of the 5g cylinder.  

I have now passed FOUR months with the fan running, as I discussed months ago, and have not had a single internet dropping out failure.  It is obvious to me there is a heat problem with the 5g cylinder.  

I've been having issues for 4 weeks and support blamed towers that were being worked on and then just kept saythey were investigating the issue, being super nice, but never offering a solution. 

I felt for heat and felt a little but didn't think it was bad, I decided to try a laptop cooling fan anyway and within around 10 minutes everything came back blazing fast.  It's stayed so far longer than it has in 4 weeks.  


I decided I'd search to see if anyone else agreed about the overheating and I found your post.  I think you are definitely right and it irritates me badly that they know about this and never say a word!

My TV is over the internet and it has been awful.  Thank you for sharing your findings  

I bought usb fans for my overheating issue. And the gateway still self reboots all the time. In fact, the majority of the time, I use cellular in my home, and not through the gateway. 

when it DOES work, I get crap speeds I’m literally at a loss of what to do. The only other internet option where I am is Spectrum and I left them in October for TMobile  suggestions? Because T-Mobile customer service isn’t helpful at all  


I’ve done the reset reboot and everything then found what works , I have my gray tmobile 5 g on its side with a holmes small air purifier on high blowing air into the top side of it , and it has worked for over a month like this , it has fixed the thermal issue . Engineers should have put fans into the modem!

I can say without a doubt this is an overheating issue. The first gateway lasted 8 months without any issues and only 2 bars. D/L speeds of over 50 most of the time close to 100. Once the issues started the gateway would reboot every 5 to 10 minutes during heavy throughput, 4 to 5 devices connected. When I lost connections, I would walk over to the gateway and it was powering back up every time. This went on for several days until I got it replaced with my second gateway. Within a few days the same problem started and I put a fan on it and the problem went away. Took the fan off and problem came back. I’m now on my 3rd trash can and have not seen any issues yet. I do not have the time nor am I going to do what T-Mobile should have already done, collect the stats to confirm the issue and rectify it.    


To above:


100% a thermal issue... After sticking a 80mm fan on the side the issues are gone..  Went through 3 routers all having the overheating issue..  And losing signal/having to soft reset after only a few hours of use. They could have charged another $10, put a fan in there and saved 98% of their customers headaches..  Ever since cooling it down it's been a beast. Im rural and this is by far the best internet option for me. And it's not terrible with gaming as long as the signal is good and router is cool. 


What do you say?


Definitely a heat issue. More than a few times I was having issues with slow speeds. Couldnt even run a Google speed test or Jitter it was so slow. So went to the router (did not power it down) and turned on the fan and pointed it right at it and within 5 minutes my speeds go up. You can feel the outside. Its not hot hot but pretty warm. Once it cools down speed goes up. 

Tested this method time and time again. Its like “hey my internet is slow. Oh yeah I forgot to turn the fan on.” 

Hope this helps. 


A USB fan will not plug into the back of the Sagemcon, it has to be a c end to plug in. 

Userlevel 4
Badge +3


A USB fan will not plug into the back of the Sagemcon, it has to be a c end to plug in. 


Just buy an adapter from whatever type of USB plug your fan has to a USB-C plug. My fan has a USB-A plug on it, so I use a USB-A to USB-C adapter, and the fan works perfectly.