just got my fathers 77 gmc 2500 siera classic camper special. 98,000 miles he bought it new. i have been able to get everything working again except the factory cruise control , all vacume lines are new box has power, how do i check box or what could be wrong ?
If everything is hooked up correctly, and your speedo is working, you probably need to replace the cruise control transducer, what you are calling the "box." Very simple to change. They come in two wire and three wire versions, so just make sure you get the correct one. They're about $60. JP
