My RT-AC86U Merlin 386.2 shows only Core 1 (Core 2 disappeared), High temp --> How to adjust to be a normal

[JKP]

Hi,
As per topic; My RT-AC86U Merlin 386.2 shows only Core 1 (Core 2 disappeared), High temp --> How to adjust to be a normal
My AiMesh System is...
AC86U...main router
AC88U...node #1...Ethernet cable backhaul
AC68U...node#2...Ethernet cable backhaul

All of them were applied Merlin 386.2
Usually number of clients are 35-52
Ambient temperature 28-35ฺฺ Degree Celcius, no additional fan

Many thanks for your suggestions.

 

[Wade Coxon]

This has been covered at exhausting length in a few threads now. Here is one that is dedicated to the topic and should contain all the info and links you need:

Router temperatures

Hello everybody With this release, temperature of my RT-AC86U has risen again. It's around 96°c. and logs shows CPU turned off due to excessive heating. CPU Wait is ENABLED. Anyone else experiencing this? Thanks

www.snbforums.com

In short, the 386.x firmware series introduces some new CPU hungry features, in combination with switching off some power-saving settings that result in pushing some rt-ac86u units over the line from "quite hot" to "too hot" due to a poorly designed thermal interface between the CPU and heatsink.

The heat issue was actually much worse on the initial 386.1 beta as there was an additional CPU WAIT feature that was disabled by default which caused a very steep rise in temperatures.

You can switch the power saving "Energy Efficient Ethernet" option back on via the command line, and you can also cut down on heat generation by using as few LAN ports on the router as possible (use an external switch if you need more connectivity).

Those measures can drop your temperature a good 10 degrees or so and get the CPU back into a safer zone.

To go any further, you can install an aftermarket fan to bring temperatures down, or in an extreme case, you can disassemble the router and fix the thermal contact issue, but that comes at some risk.

The info you need should be in that link.

 

[JKP]

Hi, many thanks for your advice about reduce the heat generation and heat reduction. I try to fix it as commented.

 

[JKP]

Update the result after installing 2 Fans (5V 60mm.) on AC86U backside and push-in airflow.
That's so a big improvement - decrease around 36-37 Degree Celsius.
Before: CPU temp...104 Degree Celsius
After: CPU temp...67-68 Degree Celsius @ambient temp 30-31 Degree Celsius....

Both Core 1 and Core 2 are working fine.
Log file:
Apr 6 19:41:39 kernel: thermal cooling_device1: turn on CPU#1
Apr 6 19:41:39 kernel: CPU1: Booted secondary processor

3 Gigabit LAN port are occupied.

Thanks for your advice @Wade Coxon.
and give credits to all folks contributing in this thread...

Router temperatures

 

[Tech9]

Good job and fast reaction, @JKP. See what happens with copper shimmed CPU on AC86U and a fan:

Why is this overheating happening I tried to explain in my post here:

Router temperatures

yes, and even the slightest bit helps. I had wired a 120mm 12v fan to a usb plug and taped it on my 86U and got 66C temperatures. This last time, I just set it standing on its edge about 4 to 5 inches away, not "pointed" at the chip, just towards the router, and that got me the same 66C temps...

www.snbforums.com

 

[mromero]

This has been covered at exhausting length in a few threads now. Here is one that is dedicated to the topic and should contain all the info and links you need:

Router temperatures

Hello everybody With this release, temperature of my RT-AC86U has risen again. It's around 96°c. and logs shows CPU turned off due to excessive heating. CPU Wait is ENABLED. Anyone else experiencing this? Thanks

www.snbforums.com

In short, the 386.x firmware series introduces some new CPU hungry features, in combination with switching off some power-saving settings that result in pushing some rt-ac86u units over the line from "quite hot" to "too hot" due to a poorly designed thermal interface between the CPU and heatsink.

The heat issue was actually much worse on the initial 386.1 beta as there was an additional CPU WAIT feature that was disabled by default which caused a very steep rise in temperatures.

You can switch the power saving "Energy Efficient Ethernet" option back on via the command line, and you can also cut down on heat generation by using as few LAN ports on the router as possible (use an external switch if you need more connectivity).

Those measures can drop your temperature a good 10 degrees or so and get the CPU back into a safer zone.

To go any further, you can install an aftermarket fan to bring temperatures down, or in an extreme case, you can disassemble the router and fix the thermal contact issue, but that comes at some risk.

The info you need should be in that link.

12 volt CPU fan derated to 5 volt using Merlin 384.19