Ex120-3 beeping with key off

I inherented this machine from my old boss from ten years ago that now subs work out to me. I have done lots of work to this machine over the last ten years, I was telling him I no longer wanted to deal with it so he told me it was mine to keep. As soon as you try to start it looks normal on the dash and led button lights. Then when you turn the key to off, everything remains on except for dash lights ie oil pressure, glow plug light area then a constant beep until you disconnect the...

Ex120-3 beeping with key off

Ex120-3 beeping with key off