Prohashing Mining Pool Forums

Hey everyone,

Need some serious help here. I noticed that one of my L3s had its hashing power drop to nearly zero.
The problem I am noticing has to do with the speed of fan#2 only spinning at around 870 rpm --compared to 4900rpm usually.
There doesn't seem to be any issue with any of the chips and the temperature is nominal.

I read on the Bitmain site:
9.Issue: The miner works with normal hash rate when it was booted firstly. After a while, there is no hash rate.

Reason: One of the fans was not detected. Only when two fans are detected can miner work well.

"Switch the fan and IO board in turn to find out which one is defective."

It is asking me to replace the fan?
What could be the problem exactly, and does switching the fan resolve the problem?

800 - 900rpm is roughly what a fan spins at when it fails and is being driven by the air from the other fan. That's why your hashing has stopped. If you want to test, you can switch over the fan leads on the control board to see if the "other" fan shows the same low rpm.
I keep several spare fans and when I see this happening, I just replace the fan without troubleshooting. It has always fixed the problem for me. The more troubleshooting you do with a problem like that, the more likely you are to fry your miner.

Also, those are some pretty Heavy Duty 4-pin fans on the L3+.

Pretty sure they have a feedback as to their RPMs for the control board sensors.
So guessing server grade fans. Be sure to replace 4-pin with 4-pin fans.
I'm not sure you will be able to find them at your local BEST BUY store, you may need to order one online.
I had a fan blow out and I tried with a 3-pin and I do not think the miner would operate until the 4-pin replacement was plugged in.

Think I got 3 fans when I had 1 fail just to be covered for down the road.

CSZiggy wrote:Also, those are some pretty Heavy Duty 4-pin fans on the L3+.

Pretty sure they have a feedback as to their RPMs for the control board sensors.
So guessing server grade fans. Be sure to replace 4-pin with 4-pin fans.
I'm not sure you will be able to find them at your local BEST BUY store, you may need to order one online.
I had a fan blow out and I tried with a 3-pin and I do not think the miner would operate until the 4-pin replacement was plugged in.

Think I got 3 fans when I had 1 fail just to be covered for down the road.

You have to use the proper 4 pin fan. The RPM speed is part of the feedback. If you have more than one L3+ miner, it's worth picking up a couple of fans for spares. If you have only one miner then you'll have to decide if it's worth the money since they are barely profitable. You can find them on ebay but be sure the RPM and amp rating are the same or very close. Buying from BITMAIN once you pay for shipping isn't worth it. BTW- if you're going to buy 1...buy 2 in case one doesn't work when you get it or the other fan fails.

Worth a try
I had one of my 18 L3s come with a fan that just did not want to spin. I disconnected it, looked around inside, I connected the other fan to that power, and it worked, cursed some, put it back together the way it came, and it just started working haha.
Mad4mining is right however, you can get replacement fans for these on Ebay, but if you got one you can swap out or test that unit's fan on the failed fan's connection, you will better know if you need a new fan or not.
Goof

Edit CS=Mad4mining

Thanks for all the great feedback, everyone.

I've replaced the fan, it seems I still have the same problem where the fan speed is still running under 500rpm.
I'm going to switch the cable headers on the board to see if the problem goes to the other fan, and if so, I guess it's a problem with the board?


**I've switched the fans and the issue persists but instead of Fan 2 being slow, now it's Fan 1, doesn't this mean it's the fan and not the board?**

If the same fan/replacement plugged into 2 different ports both gives 500 RPMs and the good fan plugged into both gives 4500, then I would say its a bad fan and NOT a bad board.

Did you get a replacement 4-pin 4500+ rpm server/system fan with proper feedback pin?

Even if its backwards it should still function, but double check the arrows on the edge of the fan molding to make sure it's pointed the correct way.

CSZiggy wrote:If the same fan/replacement plugged into 2 different ports both gives 500 RPMs and the good fan plugged into both gives 4500, then I would say its a bad fan and NOT a bad board.

Did you get a replacement 4-pin 4500+ rpm server/system fan with proper feedback pin?

Even if its backwards it should still function, but double check the arrows on the edge of the fan molding to make sure it's pointed the correct way.

I've switched the ports that they were plugged into to see if it was just the fan, but even with the new fan, and having tried both old ones, and still getting low RPM, I've determined it's the bored. Most people seem to simply switch the fan and see the problem resolved, but for me it's not the case, unfortunately.