Why would the windshield wipers quit working in a 2004 Ranger?

Answer 1

The system is more complicated than it needs to be. I guess this is one of those "better ideas." Power is controlled to the circuit through relays which are switched on by something called a "smart juction box(SBJ)." It is the fuse panel, but it has electronic computer circuitry built in. Why? Who knows, but that is the way somebody at Ford decided to make it. Anyway ground comes out of the SBJ to the coil side of the wiper relays(there are 2 of them) in the BJB-Battery juction box. The power side of the coils are fed by the ignition switch-on circuit. When the SJB decides to turn on the wiper relays, it provides a ground to the BJB relays which have power on the other side of the coil windings whenever the key is on. You decide what you want the wipers to do, by turning on the switch. The switch sends a resistance signal to the SJB, which in turn, makes that happen by turning on the appropriate combination of relays. There is a high speed relay and a low speed relay. Intermittant speeds are created by having the SBJ time the switching on and off of the relays. So now you know, that you have a switch, SJB, BJB, two relays(plus a third for washer operation), a fuse(position #5 in the SJB), the wiper motor itself, and all the wiring. A problem anywhere at all in that system can cause a wiper to not function.