When I put the key in the ignition of my 1983 300 SD it turns freely and seems to engage in all the positions but nothing at all happens. It seems to be stuck in either the Accessory or the On position because the warning lights on the dash (next to the glow plug light) remain on and the ignition buzzer continues to buzz. I can't get the glow plug heater light to go on, nor can I engage the starter. I disconnected the battery to keep it from running down. I also looked under the dash at the back of the switch but all the wires were connected and tight. I'm thinking the whole switch needs replacement (although this was done about 8-10 years ago)? Any suggestions?