What voltage do you get with tractor off and how does that compare with tractor on? do you get any voltage on temp sender? did you check fuses any? as the name implies voltage regulator work along with the alternator to " regulate" good charging voltage. That should not directly effect gauges. need to dig in more.
If the tractor starts and runs normally I would look for a main fuse or possibly a defective ignition switch. Of course if it's not charging the battery will eventually go dead from starting the tractor.