Ignition Problem

Hi all, I have a 93 LSE with a 300tdi conversion, it has recently developed an ignition issue. When I am turning off the engine the ignition needs to be in position 0 for it to turn off the engine.
Any idea's as I'm at a loss, I have noticed that there is power going to the fuel pump with the ignition at position 1 and I've rummaged around the engine bay to see if I can notice anything.
I'm in the middle of replacing the heater fan so I have the dash out and have tons of room in the cab to see if there is any wiring issue causing this or is it the ignition itself that is causing the problem?????
Thanks in advance

Try a squirt of switch cleaner - NOT WD40 or branded equivalent - in the keyhole and work it a few times. You may find that the slides and contacts inside have got a bit gummed.