Fuses for the hazard flashers and turn signals in your 1999 Ford F-150 are in the passenger-compartment fuse panel. The fuse panel is below the dashboard, to the left of the steering wheel, near the brake pedal. Check the yellow 20A fuse in slot No. 13 and the red 10A fuse in slot No. 23 first. If the fuses are good and the electronic flasher isn't the problem, you may have a faulty multi-function switch.
Park the truck in a well-lighted area. Open the driver's door to the full-open position. Adjust the seat to its full-rear position.
Lay down on the floorboard and look up under the instrument panel around the base of the steering column to locate the auxiliary relay box. There will be a blue relay and a black relay plugged into the box.
Pull the blue flasher relay straight out of the box. Align the contacts on the new relay with the terminal slots in the box, then plug the new relay in. Test the operation of the turn signal flasher.
