The glow plugs usually either work correctly or not at all. We recently had an issue on a low hour truck and the relay was bad.
Just a fyi..
On the newer equipment, the glow (QGS) controller for the glow system is built into the VCM. Also, the newer trucks with the QD32 engine only use's one relay where as the older models used two.
This is ONLY to be used to report flooding, spam, advertising and problematic (harassing, abusive or crude) posts.