Truck will not start
Ok 03/99 F350 will not start. Drove it to work, drove around at lunch. After work no start. Clicks but no rotation of starter. Thought maybe I left my phones car charger plugged in pulled out the Edge and read a P0603 code. Researched on here and it was really I throw away code I seemed to gather, but the batteries were old anyway. So 2 brand new batteries were put in. Truck will still not start. Just click and nothing. I'm brand new to electrical to diesels so I went to Advanced and asked for a starter relay since the little black box drive side engine bay clicked and had 2 relays inside. After a 15 minutes explination on how diesels did not have these, he hands me a universal selenoid. I told the guy if these are what is wrong the truck has 2 of them on the top of the motor, another 20 mintues of him "teaching me" he said only one on the firewall. I walked out of their store.
Any input on what can be the cause of the trucks problem?