I cannot get the glow plugs to work on my F350. When i turn the key on I have power to the two small leads on the glow plug relay and I have constant power to the one big lead but no power to the glow plug lead. I was told the relay is bad but I tried 3 brand new relays and they all do the same. Any ideas on what can be wrong? The truck has gone thru a frame off restoration. All electrics work except this problem.