1986 Suburban Electrical issue

This is a hard to answer this question,but i will say this,there is a short,if it only doe,s it under electrical load,i would start by checking the truck,s battery draw under this load,some suburban,s have to have a beefed up alternator,to tote it,s massive wiring system,may need to upgrade,the truck probably,has a 13.2 amp alternator,you can get one that has 14.3 amp,may help,and again this old of model there could be other wiring issue,s all so.