Electrical nightmare
 

In the midst of a K3500 crewcab, 4x4, 6.2 head swap something happened. Not sure what but now my glow plug relay, glow plug controller, volt meter, glow plug indicator light, and fuel gauge do not work. (Already replaced the glow plug relay and controller, glow plug inhibit switch tests OK, low voltage is going to the new glow plug controller brown wire, nothing out on the light blue wire), Symptoms were present before and after the new controller and relay were put it. Any ideas what I might have done? Thanks in advance, Dewey

Broken/missed ground somewhere,you don't post the year involved so I can't direct where to look.

electrical nightmare
 

Sorry, 1983. Seems like there are a billion grounds on this motor. One battery to frame, one battery to block, one block to firewall, and one from an insulated connector on the driver side fenderwell to the lower AC bracket. all are squeeky clean. I will keep digging for more grounds. Thanks