i have a ( 1991 Gmc Sonoma 4.3 v6 ext cab truck )
i went to go and start it the other day it worked i then turned on my heater and the truck just died and never re-gained it's power back
with that said
 
i changed my ( ign switch on the lower column ) and changed the fusible link in the starter soliod ) neither one of these did anything for me i checked my battery and it is good
checked links on m alt they are good
 
i have head lights brake lights and a dome light that works
 
when i put my key in and tuen it to me i get the radio to work but that is all that works in my truck

no dice i looked at the power wire going to the starter and it's good
looked at the ground wire and it's good
 
i re-re-placed the fuseable link on the soloind no dice
 
looked for loose wires around the engine all good
 
looked under the dash panel at the fuses
 
all are good -except i found one ( shunt fuse ) that would not light up on my tester light what does a ( shunt fuse ) do any way