That seems to be quite a common problem on the 1998 models , from what I have read it is caused by bad soldered connections inside the radio.
http://www.modifiedlife.com/1998-ford-explorer-car-radio-stereo-wiring-diagram/ Color codes for factory wiring
The factory radio does not have an aux Jack.
www.the12volt.com has all factory wiring diagrams for free.
Radio AAHS ended in 1998.
With premium sound system you have to bypass the factory amplifier and pretty much splice into the factory wires after the amplifier. A good place for questions is the www.clublexus.com forums or the www.lexusownersclub.com forums. Search the forums and your question has already been addressed. Myself i have a 1999 gs400.
junkyard
http://www.modifiedlife.com/1998-ford-explorer-car-radio-stereo-wiring-diagram/ Color codes for factory wiring
It displays on the factory radio. There is a button on the OEM radio to either show the time or radio station.
where is the factory amp in a 1998 2dr ford explorer sport
6x8
The radio display on my 1998 explorer lmtd. has a mind of its own. Fades in and out-usually out. If you've checked all the fuses and wiring, its probably the display itself, (esp. if it fades in & out like mine). I am an avionics tech. and I have to replace these types of displays on a reg. basis. They are flaky by nature.
I believe the push button switch for the factory fog lights is in the center stack of your dash , just to the right of the radio , near the bottom of the radio
The factory radio does not have an aux Jack.
the radio needs to be fixed or replaced
I think that the connections are different. 95 through 97 are the same but that was changed in 98 and I think it is still the same. A wiring connector may be available for about $20 from a internet company in Missouri that specializes in factory radios.
Ford Explorer radio display fixIf it is a case where everythying works fine but the display is blank, it can be fixed. It is caused by a design flaw that Ford acknoledges but refuses to fix. Anyway, I just sent my radio away to be fixed and will have it back today. I used these people www.videoservicestop.com . It cost me $110 and it is guaranteed for one year. It took less than a week from the time I shipped it until I received it back. .
open the passenger door in that fuse box