How do you know which fuses go to what on a 1986 Ford Econoline Van?
Read your owners manual
Answer Look in the engine compartment for the power distribution box. There will be some fuses and relays in it. The top of the box should let you know which one it is. There is a diagram in the owners manual (page 125 for fuses, page 129 for relays). Check out http://vehicleownersmanuals.blogspot.com/ to download it for free.