Last time I checked, the clutch gets 12 volts and ground. The 12 volts it gets is after all of the pressure switches - if you have 12 volts and ground to the clutch, the rest of the electrical is up to par enough to engage the clutch.
I would check the tolerance in the clutch to see if the electromagnet force can lock it up.
If you can post what it's doing, the smart folks in here can probably help a little more.
Good luck.