Hi guys. I have a 2004 f250 with the 6.0. The other day the battery light began to flicker intermittently. I have a scan-gauge and it said that the voltage was 11.6 volts. The next day I checked the batteries and noticed that the positive leads on the batteries were corroded. before i cleaned them I checked the voltage on the batteries and they both read 11.8 volts. I cleaned the positive post and started the truck. After running for couple of minutes the voltage went up to 13.9 volts. I turned the truck off and checked the voltage on the batteries and both were reading 12 volts. After driving for about 5 miles the battery light began to flicker again intermittently. The scan-gauge showed the voltage at 13.4-13.6 volts. Do I have a bad alternator or batteries?