The Chiller cools off the spindle. If it's not working it may contribute to overheating. I pull the hose out (the one that pumps the Dowfrost) and make sure it has flow from time to time. Last time the Fadal technician was here he showed me that trick. Ours was not pumping and I ordered a new pump. The drive tang was broken off. It never caused the spindle to alarm out though.
Some guys on this site are more into repair than I am and may be able to describe this better than I have. I can take a picture if you need. Bottom line if the pump is not circulating the Dowfrost you need to address this issue.
Do you have a non-contact thermometer. See how warm the spindle gets. I'm sure someone here can tell you what temperature is too hot. Bearings may be going bad, they will heat up on you. Hopefully it's nothing too serious.
Good Luck,
Don
Neal must have been typing at the same time I was. Chiller and spindle bearings seem to be likely causes.
Still working in the "D".