I have tried to read as many threads as possible before posting this question. Have a glow plug system issue where the Wait Light does not come on, GP Relay cycles every few seconds about 6 times then stops cycling (GP Relay 1 year old) and no start. Batteries are fully charged, Engine Control Fuse OK, put in a working GP Control Card and still same symptoms. I have not yet changed the Wait Light bulb. If the bulb is bad would that interrupt the system from working properly? If not, is there any suggestions I can try?