What Is This Alarm Actually Saying
The meaning of Fanuc SV0444 is actually very plain: inverter internal cooling fan stopped. What does this fan do? It cools the power section of the
servo amplifier. When the amplifier is working, the inverter part and the power devices generate heat. If the fan doesn't turn, the heat can't get out, and the temperature will climb up bit by bit. So Fanuc keeps watching this fan all the time. Once it finds it stopped, it throws you an SV0444. On some Alpha i amplifiers it directly shows Alarm Code 1.
Here there's one very key difference: SV0444 says "the internal
fan stopped." It does not say "the whole servo amplifier is dead." These two things are far apart. If you don't understand this point when buying parts, it's very easy to spend big money on a whole unit, when the problem could have been solved by a fan costing a few money.
Most of the Cases We Run Into Are Like This
1. Nine Times Out of Ten, the Fan Is Jammed by Dirt
CNC equipment that has been running in a workshop for a few years — the inside of the electrical cabinet can't possibly stay clean. Dust, iron chips, oil mist, coolant mist, these things get into the cabinet every day. As the fan turns and turns, a layer builds up on the blades, and dirt can also get into the bearing. At first it turns with difficulty, the noise gets louder, and later it just jams dead and doesn't move. Fanuc's side detects it — fan not turning — and the alarm comes.
I ran into a machining center once. The operator said it suddenly alarmed 444 while running. Opened the cabinet and looked, a clump of something like cotton wool was wrapped around the fan blades, mixed with iron chips. Cleaned it off, gave it a turn with a finger, the fan turned pretty smoothly. Put it back, powered up, the alarm was gone. This kind of situation is really not rare. So when you hit 444, don't rush to buy an amplifier. First cut the power, open the cabinet, and see whether that little fan actually turns, and whether something is jamming it.
2. A Loose Fan Plug Can Also Give You 444
There's another situation that's also very common, especially on equipment that just had the amplifier repaired, just had the control board replaced, or just had wiring touched in the cabinet. The fan plug may not be pushed all the way in, or it was pulled off and forgotten to be put back, or it is plugged in but the contact is poor. The amplifier looks, no fan signal, and still alarms SV0444.
This kind of fault is the easiest to make people misjudge. Because the amplifier itself has nothing wrong, the fan is good too, it's just that the plug wasn't sorted out properly. So if the first power-up after repair alarms 444, don't first suspect the amplifier is broken again. Go back and look at what places you just touched. Fan plug, control board, panel, were these put back in place.
3. The Mounting State of the Control Board and Panel
When Fanuc repair documents mention the fan alarm, they also have you check the mounting state of the control PCB and the panel. This point a lot of people ignore. Sometimes what you repaired wasn't the fan, it was removing the control board or the panel, and when putting it back it was slightly not in place, which can affect the fan's connection or monitoring. Especially that kind of "changed a board, and a new alarm popped up" situation, many times it's not that the new board has a problem, but that something wasn't done right during installation.
The Fan Is Dirty, Can It Still Be Used After Cleaning?
This depends on the fan's actual condition. If it's only dust, iron chips, oily sludge on the surface, the fan itself can still turn normally, and after cleaning it runs steadily, then you can keep using it for now, and watch it more later. But if the fan already shows clearly wrong speed, hard to start, stuttering as it turns, especially loud noise, a sticking bearing, or it still doesn't turn smoothly after cleaning, then don't make do with it. The cooling fan is a part that works continuously for long periods. When it's already clearly aged, if you force it to keep carrying on, maybe some day it alarms again, and in serious cases it could even heat the amplifier's power section into a problem.
At this time, directly replacing it with a matching model of Fanuc internal cooling fan is more reliable than continuing to use a half-dead fan.
When Replacing the Fan, Don't Just Look at Size, If the Model Doesn't Match It's Still Useless
Once you've confirmed the fan is bad and it's time to replace it, don't casually grab one with a similar size and put it on. Different Fanuc amplifier series, different power ratings, different configurations, the fans used inside may all be different. Same size doesn't mean same voltage, same speed, same connector, same monitoring method. You'd better first find out the servo amplifier's full model, and choose against the original fan's specifications.
If you really can't figure out the fan's specific model, take a photo of the amplifier nameplate, and take another photo of the fan plug and mounting position, and send them to your supplier. That's much more useful than only telling them "Fanuc alarms 444."
Alarms 444 Right After Repair, First Review What You Just Touched
Suppose a machine was originally running fine, just had the servo amplifier repaired, and on power-up again it alarms SV0444. At this time what you should do is not immediately tear down the amplifier, but think back over the repair process: was the control board removed or not? Was the panel removed or not? Was the fan plug pulled out or not? When putting it back, was it pushed all the way in? Was the fan blocked by cables or a board? These all look like small things, but they can really make you search for half a day.
Second-hand Fanuc amplifiers also often run into this kind of thing. Some amplifiers sit in a warehouse too long, the internal fan bearing dries out or sticks, and the customer installs it and alarms 444 on the first run. Sometimes the amplifier's electronic part has no big problem, it's just that the fan reached its life, and replacing one fan lets it keep being used.
Still Alarms 444 After Replacing the Fan, Then Think Toward the Monitoring Circuit
If you've already confirmed the fan has no foreign objects, the plug is in well, the control board is also mounted in place, and after power-up SV0444 or 444 still repeatedly appears, then you have to change your thinking. At this time the problem may not be in "is the fan bad or not," but in "can the amplifier correctly detect that the fan is turning."
Here there are two possibilities: one is the fan really isn't turning; the other is the fan is turning fine, but the amplifier's monitoring circuit didn't recognize it. These two faults are troubleshooted in different directions. If you replaced with a correct model new fan and the alarm is still the same, then don't keep replacing fans, you have to consider whether the amplifier's internal fan monitoring circuit has a problem. This kind needs further professional testing.
Alarm Code 1 on Alpha i Amplifiers
Some Fanuc Alpha i servo amplifiers, when they meet internal cooling fan stopped, show Alarm Code 1 on the panel, and the CNC side shows SV0444 or 444. So if on site someone only tells you "the amplifier shows 1," this information actually isn't enough. You'd better also write down the complete alarm on the CNC screen. Different amplifier models display in different ways. When consulting, getting a quote, booking repair, give out the amplifier's full model, the CNC alarm, and the amplifier LED display together, and judgment will be much faster.
Why Fanuc Insists on Watching This Fan
Because the servo amplifier's power section gives off no small amount of heat when working. Especially when the machine runs continuously, axes move frequently, and the load is also fairly large, the amplifier itself is continuously bearing heat load. Once the internal cooling fan stops, air volume drops, and the working temperature of the power devices may slowly rise. So from a maintenance point of view, even if the machine can still move for now, SV0444 also can't be left alone for a long time. If you continue to let the amplifier run with the fan not turning, this risk isn't worth taking. The alarm itself is reminding you: the internal heat dissipation condition has a problem.
When Should the Amplifier Be Sent Out for Testing
If you've already replaced with the correct fan, and also confirmed the connections are normal, but 444 still won't clear, then it's worth taking the servo amplifier for further testing. Especially when the new fan is clearly turning fine but the CNC still shows SV0444, at this time you can't only suspect the fan. You have to confirm whether the amplifier can correctly detect the fan's turning and state. If the detection circuit is bad, the amplifier may need repair.
For discontinued or old model Fanuc servo amplifiers, professional testing is especially valuable. Because what the customer really wants to know is often not "is there a new amplifier to buy," but "can this original one still be repaired." If the amplifier's other functions are all normal and only the fan monitoring circuit has a problem, then repairing it may be more suitable than replacing the whole thing.
What Our SongWei CNC Can Help With
Our
SongWei team has long been doing Fanuc servo amplifiers, servo motors, CNC boards and these Fanuc CNC parts, and we also provide testing, repair and replacement support for servo amplifiers. If you're running into Fanuc SV0444, Fanuc alarm 444, or Alarm Code 1 on an Alpha i amplifier, it's best to provide the servo amplifier's full model, the CNC model, and the amplifier LED display together. If conditions allow, take another photo of the fan state inside the amplifier. This can help us judge whether it's the fan jammed, the plug loose, the fan itself bad, or whether after replacing the fan the amplifier still needs further testing.
Finally, once the fan is confirmed bad, you can find a matching replacement fan based on the specific amplifier model; if the fan is normal but the alarm is still there, then you have to check toward the amplifier itself.
Final Thoughts
Fanuc SV0444 or 444, the core meaning is: inverter internal cooling fan stopped. It doesn't mean the whole servo amplifier has to be replaced. Many times, it's just that cooling fan inside that has aged, or is jammed by dirt. First find out the real source of the fault, then decide whether to replace the fan, repair the amplifier, or replace the whole unit, this way is the most reasonable. For customers who need to buy Fanuc parts, giving out the servo amplifier's full model, the CNC alarm code, and the amplifier display information together is often the fastest way to confirm the correct part.
