Preheater on Voyager RG models is stand alone. if any problems with glowplugs or relay / fues you will NOT get any warning or error in engine control.

Glowplug fuse is hiden in the harness behind battery. It's just a pice of wire , I change wire after glowplug wire short with the servo oil can bracket. with 2 pices of wire and a std. fuse blok and 80amp. fuse. Working great.