S4C rebooting on it's own...

tomC

I've been having some trouble with one of our controllers (S4C/M98/6400) - it was spontaneously rebooting on it's own in the middle of a program.  When we looked into it we found that three of the fans for the Drive Units were dead!  Yikes!  Replaced the fans and was fine for a while, but it just did it again.  I'm afraid that maybe one of the Drive Units is permanently damaged.  Does anyone have any experience diagnosing these issues?
And on another note, does anyone know the original CFM specs for Drive Unit fans - I got the closest match in voltage/amps that I could find on short notice, but I couldn't locate the info in the manual (it just says fan unit in the manual).

Thanks,
tom