92 ford van cruise control?

Where can i find a wiring diagram or breakdown sycamatic for the cruise control or speed sensor for a 1992 ford E-250 econoline van. I have looked in several different brands of shop manuals and they just have general info.I need voltage details because i am not getting power to or from the cruise switch on the steering wheel.If it was just me i wouldn't care if it worked but its my dads and he has alot of problems with his legs and feet.I dont have the money to take it to a shop to fix it.I will be very thankful for any kind of help. Thank you and God bless you