The good news is the fault code (P1395) indicates the problem is with one or more of the glow plugs on only Bank 1 of your Ford F350 Diesel. This at least eliminates any of the glow plugs on Bank 2, plus indicates the fault is not effecting the entire bank and should lessen the diagnosis required.
Trouble code P1395 is a monitoring fault; meaning your Ford's ECU (engine control unit) has detected a failure while monitoring the glow plugs on bank 1. The glow plug system is monitored whenever the glow plugs (either bank 1 or bank 2) are commanded on for more than 35 seconds and the truck's battery voltage is between 11.5-14 volts. P1395 (for bank 1) or P1396 (for bank 2) will set if the reading is less than 39 amps on either bank. Monitoring usually occurs at start-up, and as such, if the fault is not repaired, you'll notice the check engine light turn on soon after starting the engine, even if the trouble code has been cleared from the ECU.
The fault is more than likely caused due to loose fitting pins in one of the glow plug circuit connectors. You should inspect all bank 1 glow plugs, glow plug wiring and connections. Any electrical fault which might cause high resistance in the glow plug circuit and not allow at least 39 amps to be measured by the Bus Bar will trigger a P1395. It should be noted that P1395 indicates one or more glow plugs are failing the monitor, as opposed to P1391 (P1393 for bank 2) which indicates all four glow plugs on bank 1 are experiencing a fault. Should this have been the case, we'd recommend inspecting for a complete defective glow plug circuit and/or glow plug relay.
