If a Midnight crane displays USW ERR, keep it out of paid play until the fault has been investigated. A restart that clears the display is useful evidence, but it does not establish that the underlying problem is fixed.
Research limit: an exact US Fun Midnight service manual defining this code for a specific controller revision was not verified during this guide's October 20, 2026 research. The letters alone do not confirm an upper-switch fault or identify a replacement part. This is a safe fault-isolation and service-preparation guide, not an official Midnight repair procedure. Obtain the matching manual or written guidance through US Fun's official contact page before electrical testing or adjustment.
1. Capture the failure before resetting anything
Start with the exact display, not a paraphrase such as “crane broken.” Photograph the message clearly. Record whether it appears at power-up, when a play starts, during lowering, during lifting, while returning to the prize chute, or after a prize is delivered. Note where the claw and carriage stop.
Make a brief record of the last normal activity. Was the cabinet moved, cleaned, refilled, serviced, or supplied with a different prize mix? Did the problem start after a power interruption? Does it occur every time, only after several plays, or only near one side of the cabinet? These observations can narrow the technician's next test without requiring a diagnosis from a short video.
If the cabinet is safe to observe, record the failure from outside with all guards and doors in their normal operating positions. Do not recreate an event involving grinding, a stalled motor, damaged wiring, or uncontrolled movement just to obtain a better video. Write down what happened instead.
2. Separate guest protection from service access
Disable paid play using the venue's established method, label the game unavailable, and handle any affected customer's credit under the refund policy. Tell the next shift which game is isolated and why. An error message on the display is not a reliable substitute for removing an unavailable game from service.
Before reaching inside, switch off, disconnect power, and control access to the plug. Address stored mechanical energy and unsupported moving parts through the machine's service procedure. OSHA's hazardous-energy standard distinguishes a controlled, unplugged cord-and-plug arrangement from situations requiring a fuller energy-control process. A power button alone does not establish safe isolation.
Internal electrical diagnosis belongs to a suitably qualified technician using the matching documentation. Do not bypass an interlock, hold a switch closed, bridge terminals, or defeat a travel limit to make the game run. Those actions can remove information the controller needs to stop movement safely.
3. Identify the cabinet and controller separately
A cabinet name is only the first identification field. Obtain the manufacturer plate, serial number, controller-board markings, visible firmware information, and the part labels relevant to the suspected area. Record previous modifications, especially replacement control boards or harness changes.
Use a phone photo for each item and a wider picture showing its installed position. A close-up of an unlabeled switch without its location may be difficult for support to interpret. Photograph connectors in place before anything is disconnected, and avoid removing labels or routing ties simply to improve the picture.
Ask support to confirm three things: what USW ERR means on that controller, which input or movement it monitors, and what the expected operating sequence is. The useful answer should connect the error to a documented test. “Try another switch” is not enough information to select the right terminals, contact type, or replacement.
4. Inspect the visible mechanical path with power isolated
After safe access has been established, look for a prize, loose cable, displaced cover, damaged cord, foreign object, or visibly misaligned part that could obstruct travel. Compare the current arrangement with the manual and any photographs taken when the machine worked correctly. Keep fingers clear of suspended assemblies and pinch points.
Record the condition before moving anything. A cord outside its intended route, a loose mounting screw, and a broken bracket are different findings. Removing the visible obstruction may be one part of a repair; establishing why it entered the movement path is another. Do not force the carriage or pull on the claw cable to “free it up.”
If the confirmed fault involves a switch, inspect its mounting and the part that is intended to operate it. A switch can remain electrically functional while a loose bracket prevents it from being pressed correctly. Conversely, an actuator can move while the internal contacts fail. Omron's basic-switch troubleshooting guide documents loose mounting, contamination, excessive force, and actuator damage as distinct failure mechanisms. These are general possibilities, not a diagnosis of this crane.
5. Separate the observation from the conclusion
| Observation | Question it raises | What it does not prove |
|---|---|---|
| The fault appears immediately at start-up | Which starting input or expected condition does the controller reject? | It does not prove that a motor or switch is defective. |
| The mechanism stops repeatedly at the same physical position | Is there an obstruction, travel problem, or missing position feedback there? | It does not establish a specific part number. |
| The mechanism reaches its expected position but the error remains | Does the documented feedback signal reach the controller? | Visible movement does not prove correct electrical feedback. |
| The switch visibly moves or clicks | Do its documented contacts change reliably under the approved test? | A click alone does not establish contact condition. |
| A restart clears the fault temporarily | What changed, and when does the fault return? | It does not demonstrate a durable repair. |
Use this table to choose the next question, not to skip to a replacement. The same visible symptom can originate in a mechanical problem, the feedback path, a connection, or the controller's interpretation of the signal.
6. Test only against the correct specifications
A technician should use the manufacturer-confirmed procedure to distinguish the component, its wiring, and the controller input. Begin with isolated inspection and documented checks. Any powered measurement needs the correct test points, expected values, suitable instruments, and an appropriate safe-work method.
Do not copy a voltage, connector pinout, wire color, or switch setting from another crane. Even a physically similar replacement may have a different contact arrangement, actuator geometry, or suitability for the signal being switched. Omron's switch-selection guidance explains why insufficient actuation, unsuitable contacts for small electrical loads, contamination, and other conditions can prevent reliable switching.
Request measurements in a form another technician can understand: the test condition, exact component or documented test point, expected result, observed result, and instrument used. “Continuity good” without the terminal pair and actuator position is incomplete. The acceptance value must come from the correct service information; this guide intentionally supplies no guessed resistance or voltage thresholds.
7. Make one justified repair and preserve the evidence
Change the part or adjustment supported by the diagnosis. Keep the original item labeled until the repair has been verified. Record the approved replacement identifier, the installation guidance followed, and any setting that was changed. Retain the original setting so it can be restored if support requests it.
A movement or feedback fault is not a reason to change claw strength, win-related settings, or pricing. Mixing unrelated changes makes the next result harder to interpret and can introduce a second operational problem. Likewise, replacing several boards and switches at once may get the game running while leaving the actual cause unknown.
If the fault remains, update the service case with the new evidence. Describe exactly what improved, what stayed the same, and whether the original error now appears at a different point. Stop repeated experimentation when the next step requires information you do not have.
8. Verify the complete play sequence before reopening
After the repair, restore all guards, covers, wiring restraint, and doors required by the manufacturer. Follow its return-to-service procedure. Observe start-up, a normal paid-credit sequence, movement, prize delivery where applicable, and return to the ready state. Check several normal operating conditions rather than repeating only the easiest movement.
Use the manufacturer's required test count and conditions when specified. If none are provided, agree on a documented acceptance check with the service provider rather than calling one successful cycle a repair. Include the condition that originally triggered the fault, provided it can be tested safely.
Record the return-to-service time and arrange a follow-up observation during normal operation. If the error recurs, remove the game from play and link the recurrence to the original service record. A useful repair history shows repeat faults, not just repeated notes saying “restarted, working.”
A service request that can be answered
- Identification: Midnight cabinet serial number, controller markings, firmware if available, and relevant photographs.
- Fault: exact USW ERR display and the point in the play sequence where it appears.
- Conditions: frequency, final claw position, recent work or refills, and whether a restart changes the behavior.
- Inspection: visible findings with power isolated, without interpreting them as a confirmed failed part.
- Tests: only documented tests already performed, with expected and measured results.
- Request: correct manual, code definition, approved diagnostic sequence, and replacement identification if a fault is confirmed.
This approach turns an error display into a traceable service case. It also gives the next person enough information to continue the diagnosis without repeating unsafe or inconclusive experiments.