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Here's my personal contribution, just as additional reference:
  • RT-AC86U manufactured in 2019, running in Router mode
  • No add-ons, no VPN, no ethernet connections, 2.4GHz radio at 20MHz, 5GHz at 40MHz (80MHz is not currently needed, resulting in 4-5C lower 5GHz temperature)
  • After upgrading from 384.19 to 386.3_0 (with several NVRAM/Factory resets, etc.), I observed a consistent CPU temperature increase of 6C
  • The router now idles at 48C above room temperature - that delta is very regular within an ambient temperature range of 17C to 24C
  • No change detected after the upgrade to 386.3_2 (also a "clean" install)
Thank you all.
that you have tracked both ambient and CPU temps and have observed a (rather reasonable) stable delta is commendable.

actually, now that I think about it, the other ARM device I am following temperatures on in this house is a RasPi4 set up as a kodi media center/streaming box and its CPU temp varies +/- 5 degrees from 50C between idle and activity. 50C is a decent temp AFAIC for SoC machines (most electronics, actually) to run at for a long time - all it really needs is decent airflow to stay in "the zone"...so if your AC86 is getting too hot for your tastes, look to router placement, and try blowing some dust out before getting crazy with fans/active cooling. (the replacement of the thermal pads with actual metal heatsink material, while ridiculously awesome in result, is beyond most peoples' abilities around here)
 
I left my AC86U on 384.19, since I was not comfortable with the big jump in temperature when I went to the first 386.x release. I recently updated it to 386.3_2 and the temperature is now much closer to how it performed on 384.19. So far, I’ve observed only a 10 degrees increase at most for all three readings.
 
I didnt set any cooler or anything, this is temp when 5g is off, with 5g temp goes up to 80+
IMG_20210924_165849.jpg
 
I bought AC86U an year ago and noticed it was running on 100c+- constantly So i bought a cheap 5v usb fan and it was blowing air at the ack of the router and i could reduce the temps to about 80-85c.
From seeing some people here bought an copper shim and used it with a thermal pad and got quite good results without using any fan. So i bought 1.5mm Copper shim and had some Thermalright Odyssey 1.5mm thermal pads laying around..
I opened my unit and after i removed the "heatsink" there were no thermal pads none on the WIFI chips and CPU. Don't know if that how it supposed to be or not by anyway...
I put the thermal pad on the cpu chip and on top of the pad i put the 1.5mm copper shim that i bought.
This is my results with 18 devices connected one of them is a NAS, downloading 10gb file and also at the same time playing 7 hour 4K60 video on Nvidia Shield also on Wifi, yeah not the best but that's typical usage in my case,
Room temp about 28-29c.
Temps never went above 70c while downloading 10gb file and playing 4k60 7 hour video on YouTube at the same time and that's without using any fan. Pretty happy now with the results :)
Now i wonder if i should try putting some thermal pad on the wifi chips as well since they had none from the beginning or nah... :D

ac86uboard.jpg


ac86unewtemps.jpg
 
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people have had lower temps with both the copper shims and a fan...40C or lower IIRC. You couple the heat source with a heatsink and then force air across that. More heatsink surface area meeting more airmass and that heat energy will go away very quickly.
I'd love to see if anyone can get it SO efficient that the processor temp is the same as room temp
 
I opened my unit and after i removed the "heatsink" there were no thermal pads none on the WIFI chips and CPU. Don't know if that how it supposed to be or not by anyway...
I don't think so. If you look at photo 10 of the FCC filing it clearly shows that there are meant to be thermal pads for those three chips. Looks like they were accidentally left out at the factory which would explain your initial temperature problem.
 
I don't think so. If you look at photo 10 of the FCC filing it clearly shows that there are meant to be thermal pads for those three chips. Looks like they were accidentally left out at the factory which would explain your initial temperature problem.
Yup that's what i though...
Anyway it's much cooler now without the fan and will be even more when summer ends.
Any clue what thickness the pads on the wifi chips? @Tech9
 
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Any clue what thickness the pads on the wifi chips?
No idea. The FCC documents don't go down to that level and it's something that could change with each hardware revision. Better that you measure the gap for your particular router anyway.
 
What CPU temps are you getting with your RT-AX68U? How is the CPU performance for you on the RT-AX68U?
 
FWIW, RT-AC68 user... had this router for many years now, and it felt like it was getting warm, so I bought the dual-fan kit sold by AliExpress (mentioned earlier on this thread - thank you!). Got it today, put it on.

Room temp = 72F (22C)
Original temps = 53, 57, 84C
With dual fan, it dropped to these values in about 30 minutes = 42, 46, 61C

All are on 384.19 FW... I resisted updating because there were mixed reports of increasing temps, so I figured I should do this before updating. Next step will be to update the FW to the current version... but probably not until the weekend.
 
Any clue what thickness the pads on the wifi chips? @Tech9

The RF chips gap is about 1.5mm. You can use 2mm pads, but it depends on the material. The original pink ones are very soft and squishy. If yours are similar, cut the pads smaller than the cutout in RF shield to allow expansion. The CPU gap is about 2.4mm.
 
The RF chips gap is about 1.5mm. You can use 2mm pads, but it depends on the material. The original pink ones are very soft and squishy. If yours are similar, cut the pads smaller than the cutout in RF shield to allow expansion. The CPU gap is about 2.4mm.
I used Thermalright Odyssey pads on the cpu mod i did, they are pretty soft from what i can tell.. softer than the Arctic Cooling pads.
 
Thermal transfer pads are different for different applications. The ones Arcadyan used (the manufacturer of most Asus routers) are perhaps uretane sponge with silicone grease. Those are the soft gap filler ones. Some thermal pads are aluminum/zinc oxides and support mesh sandwich type, used for fine imperfections. Those are the hard ones, used between IC/transistors and direct contact heatsinks. You can easily tell what type yours are. The spongy ones are thicker and feel like oily rubber, the hard ones are thin and brittle.
 
Thermal transfer pads are different for different applications. The ones Arcadyan used (the manufacturer of most Asus routers) are perhaps uretane sponge with silicone grease. Those are the soft gap filler ones. Some thermal pads are aluminum/zinc oxides and support mesh sandwich type, used for fine imperfections. Those are the hard ones, used between IC/transistors and direct contact heatsinks. You can easily tell what type yours are. The spongy ones are thicker and feel like oily rubber, the hard ones are thin and brittle.
The ones i used on the CPU pretty soft, I've got an Arctic Cooling Pads and they are harder.
I'll try with 2.0mm first and if it will be too much, I'll switch to 1.5.
 
Since going from 384.19 to 386.3_2 on my AC86U and noticing the temperatures were up, but not as bad as the initial 386.x release, I thought I would monitor the temps for a bit earlier whilst normal use was underway, so simultaneous home working, console gaming, video streaming, both wireless bands active, and the CPU peaked at 83 degrees.
 
FWIW, RT-AC68 user... had this router for many years now, and it felt like it was getting warm, so I bought the dual-fan kit sold by AliExpress (mentioned earlier on this thread - thank you!). Got it today, put it on.

Room temp = 72F (22C)
Original temps = 53, 57, 84C
With dual fan, it dropped to these values in about 30 minutes = 42, 46, 61C

All are on 384.19 FW... I resisted updating because there were mixed reports of increasing temps, so I figured I should do this before updating. Next step will be to update the FW to the current version... but probably not until the weekend.
Just for the record, again with my RT-AC68... did the upgrade to 386.3_2 this weekend. Had to do a hard reset, as the GUI never came back (waited 24 hours with no luck, but routing worked the entire time). During the entire time, temperatures stayed low.
Currently seeing: 40, 45, 58 (ambient is 69F, so the slight drop here makes sense)

Bottom line, AC68 doesn't seem to get "hotter" with the 386.x firmwares, but I'll still keep the fans on as it can't hurt, after all.
 
Just read this thread, all the 24 pages as I recently upgraded to 386.3_2. I was happy that everything worked out well, until I noticed the 92-93C temperature of the CPU, while the machine was idling. I tried the
Bash:
pwr config -eee on
"hack" but it literally did not change anything, except now I see the Energy Efficient Energy: ENABLED while running
Bash:
pwr show
I am 1500km away from the router in the middle of the 4th wave of COVID-19...hm.

And before anybody asks why I needed the upgrade: I had a weird issue related with OpenVPN, and I needed the upgrade from the 384 firmware
 
upgrade from the 384 firmware
Sorry to hear about your experience, seems some aren't affected and some are. I just left 384 myself but my AC86U is on AP duty only. I was on 384.18, that seemed to me to be peak firmware for the model. I haven't noticed the temp issue post "upgrade", but in addition to going minimal duty, removing all scripts and USB drive reformatting to factory etc., the 2.4ghz radio went way unreliable, so I've retired that radio and farmed out 2.4ghz to an Airport Extreme that was gathering dust.

Back in its heyday, the AC86U was highly performant, now I'm only enjoying its excellent 5ghz coverage hoping that doesn't get messed by some latent feature creep which I'll try to avoid, we had a good run. I've graduated to an open source DIY firewall appliance with AP's model, and feel like I have my network under more secure control.
Screenshot_20211107_193103.jpg
 
Sorry to hear about your experience, seems some aren't affected and some are. I just left 384 myself but my AC86U is on AP duty only. I was on 384.18, that seemed to me to be peak firmware for the model. I haven't noticed the temp issue post "upgrade", but in addition to going minimal duty, removing all scripts and USB drive reformatting to factory etc., the 2.4ghz radio went way unreliable, so I've retired that radio and farmed out 2.4ghz to an Airport Extreme that was gathering dust.

Back in its heyday, the AC86U was highly performant, now I'm only enjoying its excellent 5ghz coverage hoping that doesn't get messed by some latent feature creep which I'll try to avoid, we had a good run. I've graduated to an open source DIY firewall appliance with AP's model, and feel like I have my network under more secure control.
View attachment 37248
Disabling 5GHz finally lowered the temperatures from 94 Celsius to 84 in average. Still not ideal, just ordered a new dedicated firewall hardware as I am fed up with tweaking things constantly.
 

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