I'm having a strange issue my RAMPS1.4 and my cooler fan. My printer seems to need to warm up(about an hour) before the fan stays on (using Sli3er and Pronterface) but using Simplify3D I have no issues at all with the fan. I just don't get it...My fan speeds in Sli3er is set to 100% and it is set to be always on. Also I can sometimes jump start the fan by giving it a little spin but doesn't always work.

Hi,

If you want your fan always on, just wire it to your PSU, and forget about any software.

++JM

Make sure you've set the minimum percentage of the fan speed so that it can spin up to rev. Use 50% as minimum for example. If auto fan control is on the fan speed depends on layer times. See the cooling section of slic3r. If the print layer time is much longer it may be that the fan speed is off or too low. Depending on the print, at the end the layer time may drop down within the range set in cooler settings, at which point the fan starts spinning.