I have been having that issue on my VF4SS. I spoke to Haas and they said to turn setting 245 off. Supposedly there is no actual sensor.
This is what I wrote to Haas; "I have been getting an excessive tool imbalance alarm #966 about once a day for the past couple weeks. I have tried to replicate the alarm and have been unable to do so. The only thing I know for sure is it happens when ramping up to speed, typically over 10k rpm. Now today I have gotten the alarm 4 times within an hour and a half. I spoke to one of your service reps, and was told that I should turn the hazardous tool vibration setting #245 to high or off. This doesn't sound right to me. This machine is 2 months old. Turning that setting off seems like putting a piece of electrical tape over a check engine light. It covers up the problem, but doesn't fix the issue. Is this a spindle issue, faulty sensor issue, something else?
This is per the Haas service tech; "There is currently no sensor, only a software provision to add one in the future. The alarm is erroneous and is no indication of any problem."
Needless to say, I have documented this just in case.
