go through std stuff like:
- battery strength
- grounds clean and tight
- pto lever disengaged and safety switch functioning
- speed control lever in neutral position and safety switch functioning
- the fusable link under the oil filter is ok but given dash power should be fine
- the brake pedal should have a safety switch in that model make sure its working. same as seat safety switch making continuity correctly
- do all the steps in section 8 troubleshooting steps of the operators manual
- check the 10a-15a-20a fuses for continuity
would be where i would start