When 601 appears, it simply means the fan has stopped
A
servo amplifier produces heat while it's working. The inverter section and power components in particular give off quite a lot of heat. The
cooling fan fitted to the radiator is there to blow that heat away. Fanuc keeps watching whether this fan is turning. Once the system detects that it has stopped, it gives you SV0601 or 601.
This alarm isn't exactly the same as "servo amplifier overheating." It means that the internal cooling fan has stopped, not that the amplifier has already burned out. That difference matters, and it's one of the easiest things to misjudge on site. If the fan is the problem, fitting the correct Fanuc cooling fan may clear the alarm straight away.
Why does the fan stop? Dirt is the most common cause
After a Fanuc servo amplifier has been in use for years, its internal fan will naturally start to age. Worn bearings, increased turning resistance, or a weak fan motor can eventually stop it completely.
The working environment also makes a big difference. Electrical cabinets collect dust, and machining areas are full of metal chips, oil mist, and coolant mist. Once this dirt gets into the fan, the blades become harder to turn. Eventually, the fan may jam.
I once worked on a machining center where the customer said alarm 601 had suddenly appeared. He thought the amplifier had failed. We shut off the power first and opened the electrical cabinet. The fan blades were covered with oily dirt mixed with metal chips, and I couldn't even turn them by hand. After cleaning the fan and reconnecting the plug, we powered the machine back on and it worked normally.
Once you've done this kind of work for a while, you realize that many fans aren't burned out. They're simply clogged with dirt.
Another common situation happens after repair work. The fan itself is fine, but the connection wasn't restored properly. Maybe the servo amplifier was repaired, the control board was removed, and the fan connector wasn't pushed in fully when everything went back together. The fan cable may also have been damaged during removal or installation.
Fanuc maintenance information specifically tells you to check the fan motor connector, cable, and the installation of the related control board and panel. If alarm 601 appears the first time the machine is powered on after a repair, don't assume the amplifier has failed again. Go back and check everything that was just touched.
Once you're on site, first check whether the fan is turning
After completing the necessary safety checks, shut off and isolate the power, verify that the circuit is safe, then open the electrical cabinet and inspect the fan on the radiator.
If the fan clearly isn't turning and you can see dust, metal chips, or other material blocking the blades, the cause is fairly obvious. Remove the dirt using the maintenance method allowed for that equipment, then see whether the fan can turn normally.
If the fan isn't jammed but still won't turn, check the connector and cable. Sometimes a loose connector is all it takes. Push it back in properly and the alarm disappears. In that case, there is usually no need to replace the whole amplifier.
But if the fan makes a lot of noise, has trouble starting, runs at an unstable speed, or still won't move after cleaning and reconnecting it, the fan itself is probably worn out. Replacing the Fanuc servo amplifier cooling fan makes much more sense than replacing the whole SVM.
Does alarm 601 mean the whole servo amplifier needs replacing?
Usually, no. At least not straight away.
For a βi SVM system, Fanuc's maintenance approach is to deal with the fan-related problems first, then consider replacing the SVM.
If the fan, connector, cable, and installation have all been checked, but SV0601 or 601 still refuses to clear, the problem may not be the fan itself. It may be in the circuit the amplifier uses to monitor the fan.
If you've fitted the correct replacement fan and it's turning normally, but the CNC still shows SV0601, don't keep changing fans. There's no point. The servo amplifier should be professionally tested to find out whether the monitoring circuit or another internal part has failed.
Don't choose a replacement fan just by looking at its size
Once you've confirmed that the fan needs replacing, don't grab one that looks about the right size and fit it. First find the full model number of the Fanuc servo amplifier. Then use that model to identify the correct replacement fan.
Different Fanuc servo amplifiers may have different power ratings, internal layouts, supply voltages, and fan arrangements. Two fans can look almost identical and still be completely incompatible.
When buying a replacement Fanuc cooling fan, the most useful information usually isn't "alarm 601." It's the full servo amplifier model number. If possible, take a clear photo of the amplifier nameplate. Take another photo showing the fan connector and mounting position. Send both to the supplier. That will make it much quicker to confirm the right fan.
Don't leave alarm 601 unresolved for too long
Some machines may still be able to run after the alarm appears. The customer then thinks, "It's only a fan. The machine can still cut, so we'll keep using it for now."
But the internal cooling fan in a servo amplifier isn't optional. It cools the inverter and power section. If the fan stops and the machine keeps running for a long time, heat will slowly build up inside the amplifier. That can eventually affect how the amplifier works.
SV0601 should be dealt with as soon as possible. Don't let the machine keep running with the alarm for a long time. Even if no serious fault has appeared yet, you still need to find out whether the fan needs cleaning, reconnecting, or replacing.
If a new fan doesn't clear the alarm, check the amplifier's monitoring circuit
If you've installed the correct fan and confirmed that the connection is good, but alarm 601 still won't clear, the servo amplifier needs further testing.
This is especially true if the new fan is clearly turning normally while the CNC still displays SV0601. At that point, the fan isn't the only suspect. You need to confirm whether the amplifier can correctly detect the fan's movement and condition.
If the monitoring circuit is faulty, the amplifier may need repair.
Professional testing is particularly useful for discontinued or older Fanuc servo amplifiers. What the customer really wants to know often isn't, "Can I buy a new amplifier?" It's, "Can the original one still be repaired?"
If the amplifier works normally in every other way and only the fan monitoring circuit has a problem, repairing it may make more sense than replacing the whole unit.
In the end, alarm 601 doesn't mean the whole amplifier is dead
On applicable βi SVM systems, Fanuc cooling fan alarm 601 or SV0601 means that the inverter cooling fan on the radiator has stopped. In other words, alarm 601 doesn't mean that the whole Fanuc servo amplifier is beyond repair. A lot of the time, the only part that needs replacing is the internal cooling fan.
Only after you've confirmed that the fan and its connections are normal should you start deciding whether the SVM itself needs repair or replacement. If you still can't sort it out, you can contact
SongWei CNC directly.
