The F40 code indicates a communication problem between the main machine control and the blower motor control board. According to your symptoms, it is likely that this problem is being caused by a blown thermal fuse. I recommend the thermal fuse for continuity.

Unplug the dryer before accessing this component. Access this fuse and pull one wire off. Measure the resistance across the leads of the fuse using a volt/ohm meter. You should measure near zero ohms of resistance (continuity) if the fuse is good. If you measure infinite resistance (open), then the thermal fuse is blown and will need to be replaced.

NOTE: If the thermal fuse is blown, check for a restriction in the exhaust vent to the outside of your home. This type of problem will cause the fuse to blow.
You can order a new thermal fuse from the Sears PartsDirect website. The part number is 3390719.
This should fix your dryer problem.