Alright, here's the deal. My mom owns a 1998 Expedition and the headlights won't work on high beam. The bulbs have been changed, but they still don't work. Any idea what is wrong with it?

 

More than likely it is the multi-function switch in the column.

 

check your fuse. there should be a separate fuse for low and high beams.

 

I have a variation on this problem for which I need help. I have 1998 Expedition. Placed new headlight bulbs. Both work on low beam. When momentary high is activated, only drivers side goes to high beam while passenger side stays at low beam. When full time high beam is activated, drivers side goes to high beam and passenger goes out! High beam indicator does come on panel. Have also checked passenger side bulb and it is in good working order.

 

Have also checked the passenger side bulb and it is fine.

 

Just to be thorough, swap both of the new bulbs with each other to see if the problem moves with the bulb.

 

Good idea, but problem DOES NOT follow the bulb. Wiring split for high beams after drivers side?

 

Be aware that the harness in the steering column is notorious for melting the connector from the multi-function switch and causing high-beam problems due to the current going through the high-beam wires and the switch. It is also possible to have problems from the wires being pulled on when tilting the wheel, cycle after cycle, year after year. There is a procedure to add a relay to the high-beams which will make the lights brighter and significantly reduce the current through the switch and plug. If you find that you need to open the column, the connector is on the top. I would *really* recommend adding the relay. I don't have a link to the procedure here, but I am sure it's on this site. I did it years ago and never looked back. Had I not done it, I am sure I could have had some electrical short in the column at some point.

One thing I almost forgot... if you ever need to replace the multi-function switch, be very careful to get the correct one. The difference is in the resistance for the delay setting on the wipers. If you put the wrong one in (looks identical btw), then the wipers will do weird things like turn on by themselves, etc.

...and... if you tape the wires in the column for any reason, do not use plain vinyl electrical tape. It will degrade from the heat. Use professional self-sealing rubber electrical tape.