There are three controls for the wipers, which work together to make them run, park, and intermittent.

The multifunction (turn signal) switch sends a signal to the GEM module which tells it what function to select. The GEM then controls relays in the underhood junction box to make the wiper motor run (or park) in the selected manner.

Look in your owners manual for the W/S/W run/park relay and the W/S/W high low relay. Try unplugging them one at a time and replacing each with a known good relay. If the relays do not fix the problem, then you need to troubleshoot the switch and GEM.

You will have to take the cover off the steering column between the instrument panel and the steering wheel, then get the wipers to start running. If they quit when you unplug the multifunction switch connector (rectangular-shaped, at the base of the turn signal lever) then you need to test the switch, or try a known good switch.

If the switch does not fix the problem, then there may be a contact sticking within the GEM. This is a real problem, since I have not found a source that repairs the GEM, and Ford wants an arm and a leg for a new one, and any GEM installed in your truck has to be reprogrammed to match your truck by a dealer or someone with a very advanced scanner/programmer.

Try removing both battery ground terminals for a few minutes, then reconnect and see if that helps the problem. If it doesn't, then try switching relays and report back.