Anyone know how the stop solenoid works on a Kubota T1600?

Hi just acquired a T1600 which won't stop when the ignition is switched off, I've not applied +12V to the solenoid yet to eliminate it, but if I attach a voltmeter to the lead then no volts are detected when the key is switched off, so I assuming that whatever should apply +12V to this wire is not doing so. Anyone any idea where this voltage is derived in the off position please? Thanks in advance.