the o/d button will prevent it from going into higher gears, to test operation of the switch you need to bring your truck up to 55mph, let off the gas and hit the button, if you feel the engine slow the truck down it is functioning and your bulb is blown in your lever. If you feel no function you will need to pull the plastic cover off your column and test voltage to the switch, or replace the entire lever. Sometimes it is a simple fix of the wires that rubbed loose or broke, sometimes it is a faulty lever. If you need a replacement order dorman 905-109. Unless you want to go pay 80+$ from ford for oem. good luck

 

yep, prolly a shorted wire in the colum not uncommon

 

Mine came unplugged! Check to see if its unplugged or replace the switch


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Here's a good link for how to check the OD wires, on a '99 it's fuse #19 Not #45 as later trucks but there a re great pics here to help.

https://b7445ba3-a-62cb3a1a-s-sites...eA2je_7WPojBvlyTJq1_PO4I9cHjlG2I-HJeNoHig2XlB24AUPvYDwYDViSt5_H2&attredirects=0

 

http://www.powerstroke.org/forum/99-03-7-3l-powerstroke-problems/199538-99-03-od-wire-fix.html