This demonstration guide answers one field question about an open brake, seat, or PTO switch in the start path. Measurements come before parts, and the notes are not a generic equipment FAQ.
Diagnose before replacing parts
Start with continuity through the start-interlock series. That reading separates an open brake, seat, or PTO switch in the start path from adjacent faults that share the same complaint.
If the measurement is out of spec, treat the failed interlock switch as the primary path. If it is in spec, do not replace the failed interlock switch just to complete a parts list.
Repair the failed system
The usual correction is the failed interlock switch, installed to the documented spec for this complaint.
A demonstration shop records the finding so the next technician is not repeating a guess about an open brake, seat, or PTO switch in the start path.
Stop before you make it worse
Do not bypassing every switch because one is hard to reach. That shortcut hides the original measurement and creates a second failure.
If the machine still fails after the failed interlock switch is corrected, convert the visit to a broader diagnosis rather than stacking parts.
Written and published by Ridgeline Small Engine.