Symptoms
Knocking sound at top of loop, NDT due
Likely causes
- 01Faulty E-stop relay (most common after 3+ seasons of weather exposure)
- 02Loose terminal on safety loop wiring
- 03Failed proximity sensor on harness lock circuit
- 04Corroded ground bond between platform and main control cabinet
Diagnostic steps
01
Verify safe to approach
Lock out main disconnect. Tag the panel. Confirm hydraulic pressure is bled before opening any cabinet.
02
Inspect E-stop chain
Walk the entire E-stop loop with a multimeter. Each node should show continuity in the run state. Note any node that drops voltage.
03
Check ground bond
Bond resistance between platform and main panel should read under 0.5Ω. Anything higher and the safety circuit will throw faults intermittently.
04
Reset and observe
Power cycle the controller. Watch the fault history log on the HMI for the first three minutes of operation.
When to call a pro
- Fault code repeats after one full reset cycle
- You see arcing, smoke, or smell burning insulation
- The fault is on a primary safety circuit (E-stop, harness lock, position sensor)
- You don't have a current copy of the ride's electrical schematic