Speedometer works sometimes. If using wipers w/headlights,blower dash goes dim on 1996 Ford Ranger

Using any more than 1 of these accessory the dash goes dim ,headlights go dim , blower won 't work and the wipers go slow or stop ,directionals won't work
all while the speedometer stops working. The code p0500 came up on the scanner. Could this be more than a speed sensor ?

Asked by for the 1996 Ford Ranger