12v fan on 5v supply?

Hi DigitalVT 

I am using a GSM7248Pv1h1. The stock Delta fans that are in it are red (+), black (-) and blue (sense/tacho)

I have tried a few different manufacturers of coolers that match the spec for voltage, current, power, starting voltage etc and they all do the same thing - spin up for a second then stop.

Sunon and others use yellow wires for the sense pin, and the red and black remain the same as you'd expect. When trying Noctua fans, I'm pretty sure I had to reverse the +/- pins as they were the other way around on the switch, but it's been a while since I did that so I could be wrong!

I have also tried different fans in a GSM7248. That device has 3 fans. Trying new fans on the headers for 1 & 2 did the same thing, spin for a second then stop, but when I tried a new fan on the header for 3 it worked. The stock fan connected to 3 was 20mm deep, the ones connected to 1 & 2 were 15mm deep, but the fan on 3 was the noisest. Whether stock or not, it seems to run at full tilt from power on, and having the sense pin connected or not made no difference at all. It is deafening.

Some of the stock fans may have onboard controllers or dependant hardware that the switch may be looking for and if it doesn't see them, cut the power I guess.

I'm going to keep trying when I have time, but may eventually have to call it a day and get rid of them and drop in some silent HP equipment instead. Shame really as I have mountains of Netgear kit and would prefer to stick with one vendor.

Well, my replacements, havent spun up.

I suspect when yours have spun up, it was on the initial power up and then the temperature sensor noted the temperature was low enough that the fans could idle, and lowered the voltage, hence why yours stopped spinning as the voltage wasnt enough for those fans?

My predicament is that the colour coding on my old ones don't make sense, you'd think it would be standardised.  See picture, stock Negear fan on left, new connector on right.  My OCD is saying that Red and Black are positive and negative.  And the Blue and yellow are the sensor.  But the pins all move about!!

I agree with you. 

I would pop the pins out on the new fan, stick the yellow one in the middle and then with the connector of the new fan facing the same way up as the old one (not as in your last picture) swap the red and black around.

I've tried quite a few now and the cabling on the left is definitely correct for v+, v- and sense.

Thanks pn23.

Would you then agree with the pin config as overlaid on the right plug in the following pic?

Yes, that's how I've done every one I've tried.

They've at least spun up, but then stopped after a second.

Success.  The Pin config has worked.

The two pairs of 20mm deep fans span up briefly and then stopped, like your others.  But the deep 28mm work full time.  They are noisey!!  Having said that, the volume of air they pass is incredible!  Nothing is going to get warm inside of here!!  I'd almost consider just running one!  The noise level is about 55db about half a metre above!

Just having issues, logging into the switch.  Will report back if I can control them!

Good work!

I'd be surprised if you can control them though. The originals I have in mine run at around 55db each as well and the speed never changes.

Well, these are the ones that worked.  They do spec 40db per fan.

https://www.aliexpress.com/item/32381567224.html?spm=a2g0s.9042311.0.0.27424c4dkENqYg

I've just updated the firmware and now not a peep out of the network ports.  :smileymad:

Am going to give it a rest for a few days...

Hey DigitalVT did you manage to get any further with this and were you able to resurrect your switch?

Hi pn23,

Yeah, the fans installed okay.  My switch issue was that when I did the firmware update, I guess either it performed a factory reset or I did and came back on the default IP address (192.168.0.239), which is not in my subnet (172.16.0.x).  So couldnt see it.

So it is back and working, but noisey, still, even louder in the rack case!!  So back to square one.

Was considering the new line of Netgear switches, but don't have any cash to spend at the moment!

pn23, did you progress purchasing a replacement fan yet?

Yeah, other than the Noctuas, I have tried Sunon HA40201V4-1000U-G99 (3 wire with RPM/tacho feedback) and Sunon MF40201V3-1000U-F99 (3 wire with locked rotor detection) and had no luck. Same behaviour as all of the others, they spin up for a second then stop.

I'm completely stumped.