Thank you for your question and I understand your concern.
The "F13" fault code will display on the HE4t washers if the dispenser motor is not able to be driven to the proper position. This could be caused by a jammed dispenser motor or linkage. The dispenser motor sits on top of the dispenser assembly accessible by removing the top panel. You could make visual inspection of the linkage. If you are careful, you can apply some torque to the dispenser cam and see if you can rotate the cam and dispenser motor. Sometimes turning the cam will unjam the dispenser motor.
I hope this is helpful. If I may be of further assistance as more details become available, please reply to this post along with the model number of your washer.
If you get to the point where you need to have a service technician diagnose and repair this failure, you can schedule service through this link:
Sears Home Services.