F 250 Chimes

My 2000 F 250 Super Duty 7.3L Diesel chimes 5 times, 5 times in a row when the engine is turned on and then every 30 minutes thereafter. Does anyone know what is causing this? It sounds like the seat belt alarm but they are all connected. Does anyone know what is causing the continual chiming?

No dash lights to go along with the chimes then?

My 2000 Explorer, V6, did this when the airbag warning light burned out. Learned that trick form www.seriousexplorations.com, a Ford Explorer and Ranger forum. Check out which warning light doesn’t light up when you first turn the ignition on. I wound up pulling the dash cluster and replacing that light and all the backlight bulbs, since two of them were also burned out.