There is also a strip fuse under the cover in the glow module under the hood, located @ front left inside fender. Those modules are known for dying as well. It is what processes the temp sensor readings to time the glow plug power and light. Also I have noticed (in my car) that if one of those temp sensors becomes unplugged the glow plugs appear to not work (no glow light), might check that too. The temp sensors are located in reducer bushings in the head freeze plug holes just above the IP, between the glow plugs. Some have only one, others have two.
-Chris