WHAT YOU DESCRIBED IS MOST OFTEN A INTERNALLY DEFECTIVE BULD. (FILAMENT BROKE) CHANGE THE BULB. the multi-function switch has a internal relay that has gone bad.the multi-function needs to be replaced. that is the turn signal switch itself. I concur with the first answer, first. In other words, replacing the bulbs (even if they seem fine) is easy, cheap and often does the trick. The second answer may be correct if the easy first step doesn't fix the problem.
The correct answer is the Lighting Control Module Under Driverside dash (M.F.S.) as stated above is bad. 650-1000$$$
There are a couple of reasons why the turn signals will not work on a 1998 Ford Explorer. The light bulbs may need replaced or a fuse has blown.
Three - 1998 Blink of an Eye was released on: USA: 16 February 1998
Check to make sure all bulbs are flashing could be a bad turn signal flasher
The 1998 Lincoln Navigator trailer turn signal fuse will be in the fuse box. The trailer turn signal fuse will be one of the auxiliary fuses at the bottom of the second column.
Most likely its a problem with the turn signal/high beam switch. Its a very common problem with that year. It's an expensive part to replace. could also just be the hazard switch..try giving it a vigourus work out.
I'll check for a blown fuse(fuse relay box), ground problem, and your bulb.
multi function switch in steering column
LOOK ON FUSE BOX COVER M
The fuse for the abs system is blown. Check under the driver side of dash for the fuse panel.
Check the fuse for the brake lights. If that fuse is blown it will not come out of park.
location of thermostat in 1998 Lincoln continental
Smoke Signals was released on 06/26/1998.