Adding a fan to a hot modem

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Tomioka

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Finally got a new cable modem after years of paying a cable modem lease. It is Arris' top of the line modem but it runs uncomfortably hot so I measured the unit's temps using an IR temp gun and came out at 60C. The CPU has a heatsink and plenty vents to keep it cool but it relies on the airflow in the room. The area where the unit sits does not have very good airflow so I added a fan to force air into the unit to help with stability and longevity because it's mine now.

The unit has many vent holes on the side but relies on room airflow to keep it cool.
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Digged around in the old computer parts bin for a 120mm fan and USB cable. A USB port provides +5VDC so the fan will run at a low, quiet speed vs full speed with 12v from a computer power supply. Cut wires, strip, match red to red, black to black, splice and tape splices. Test for operation. Attach fan using double-sided sticky tape. Fits perfect!
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CAUTION FAN like on a truck's fan shroud. All up and running. Unit temps are now 30-33C, way cooler than with no fan.
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Great job. I'm sure it will increase the life of your modem. Heat is bad news.

In our server room all those small devices are put right in the way of the various fans. The place is really noisy because of all the fans but keeping the heat down is important. Besides the built in temp gauges and alarms we use an IR gun, too.
 
Originally Posted By: Rat407
One would think that it running that hot something has to be wrong not to mention the power it is using.


I have this unit and I just touched the exterior and it was barely warm.
 
They are known to run hot. Lots of refurbs.
I have the black version, bought refurbished for around $50. No issues so far, but I may end up doing this as well...had a similar setup on an old DSL modem for a few years.
 
Originally Posted By: Kibitoshin
so I added a fan to force air into the unit

Did you try reversing it to suck hot air out of the unit?

Wondering which scenario would result in better performance....
 
Originally Posted By: Quattro Pete
Originally Posted By: Kibitoshin
so I added a fan to force air into the unit

Did you try reversing it to suck hot air out of the unit?

Wondering which scenario would result in better performance....



What he has now is unquestionably the better performing setup. Sucking hot air across a heat sink is significantly less efficient than blowing cooling air across the heat sink. From someone with 40 years electronics experience.
 
I did the same on my Arris modem with 80mm fan more than 1 year ago.
As a matter of fact, it already burnt one fan so far.
I replaced it with another in the stash from old computer CPU fan.

It does increase the reliability and speed running cooler at 27C.
 
Last edited:
Originally Posted By: Quattro Pete
Originally Posted By: Kibitoshin
so I added a fan to force air into the unit

Did you try reversing it to suck hot air out of the unit?

Wondering which scenario would result in better performance....


The old negative vs positive pressure debate. Because of the unit's orientation (fan blow on side to heatsink then vents to top) the positive pressure push method seems to work well.
 
the motorola(same unit) time warner issued the shop ran so hot it smelled like it was on my reflow bench.
since it was theirs i didnt care.but when they started renting them i put a fan in mine as soon as i bought my own.ran it off the 12v but used a 24v fan.
theirs died at 2 years and its replacement 6 months.added heatsinks to the hot chips and replaced the cheap caps while i was in it.
 
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