Fuse blowing out on T1700HX

I am having an issue with my lawn tractor (model T1700HX), it runs fine but the moment I engage the PTO clutch to cut the grass, the 20 amp fuse blows out. I have tried replacing the regulator but it is continuing to do the same thing. The tractor runs fine when I unplug the magnetic clutch. The problem is when it is plugged in and I turn on the PTO switch. When checking the magnetic clutch wire that comes from the engine with a volt meter, I am not getting consistent voltage. Could the problem be the relay box? Does anyone have any other ideas of how to diagnose the problem or potential solutions I can try out? Thank you.