Hi. 
All the time Tech Pendat is showing Control Fan in Control Box Stopped, when it showed for the first time the fan was not working, so I replaced but the warning never clear 
, some times is necessary shut down the controller in order to move the robot manually(I'm not shure if is due to this), but when is running on Automatic, have not problem.
I will appreciate any commentary or suggestions.
Thanks
any fuse burned?
No, and Fans are working.
What is your system? (erc, mrc, xrc, nx100, dx100)
XRC whit UP6
This alarm occurs when one of the two fans is over the cpu fails
These fans (Brushless DC Minebea 2410ML-05W-B70) have 24v, 0v and a detector which gives an output to indicate it works and is what causes the alarm
Fans are 3610PS-23T-B30-A00 on 230 Volts, are connected directly to fuse box. So have a temperature sensor or some thing like that???.
have tried this twice...
once with XRC...replacing the fan solved the problem....
but.... 
with my Nx100, i couldent (and have still not) solved the problem. I have replaced it with a brand new fan from MOTOMAN (and seen that it is running perfect)....so i guess that the input that is mesuring the rpm on the fan might be blown.
after 8 hrs of continuesly running the robot stops, and i have to power off and power on the controller.....
Definitely replace the fan. You may need to take the whole CPU rack on the XRC to do so. If you don't, you'll get an alarm every 72 hours and be forced to power down.... 
How to clear the alarm 7491 related fan error in control box. Cooler fan functioning well and servo van on but when we push the test/ start fwd the alarm appear
