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Manufacturer
Model
What This Guide Helps With
Troubleshooting failed shock delivery caused by model operation, shock-button timing, electrode connection, battery condition, readiness faults, or internal therapy failure.
Step-by-Step Troubleshooting
1. Ensure Patient Safety First
Do not perform extended troubleshooting while the AED Plus is required for an active resuscitation.
If a shock is advised but not delivered:
- Continue CPR according to the facility’s emergency-response protocol.
- Obtain another verified AED or defibrillator immediately.
- Transfer defibrillation capability to the replacement device as soon as possible.
- Do not delay resuscitation by repeatedly testing the questionable AED.
- Keep everyone clear whenever the device may be charged.
Expected outcome: CPR and defibrillation remain available without relying on equipment with uncertain therapy delivery.
Continue Clinical Engineering troubleshooting only after the AED has been removed from patient use.
2. Identify Whether the AED Is Semi-Automatic or Fully Automatic
Confirm the exact AED Plus version.
- Semi-automatic AED Plus: The rescuer must press the flashing shock button after the “Shock Advised” and “Press Flashing Shock Button” prompts.
- Fully automatic AED Plus: The device automatically delivers the shock after its countdown without requiring the shock button to be pressed.
Expected outcome: The reported behavior is compared with the correct operating sequence for that specific version.
A fully automatic unit should not be classified as having a failed shock button merely because the button was not used.
3. Document the Exact Rescue Sequence
Obtain the operator’s description and available event data.
Record whether:
- “Shock Advised” was heard or displayed.
- The shock button illuminated or flashed.
- A countdown occurred.
- “Release Shock Button” was announced.
- “Shock Delivered” was announced.
- The device returned to CPR prompts without confirming a shock.
- The unit displayed “Unit Failed,” “Change Batteries,” or another warning.
- Anyone continued touching or moving the patient during analysis or charging.
Expected outcome: Clinical Engineering can distinguish an operating-sequence issue from an actual failure to discharge.
4. Inspect the Readiness Indicator
With the AED turned off, inspect the status-indicator window near the handle.
- A green check indicates the unit passed its readiness checks.
- A red X or periodic beeping indicates that the AED should not remain in service.
ZOLL instructs users not to place the AED Plus in service when the red X is displayed or the unit is beeping.
Expected outcome: The unit shows a green check and is not beeping.
If a red X or beeping condition is present, remove the AED from service and continue only with controlled bench evaluation.
5. Inspect the AED and Shock Button Externally
Check the enclosure and shock button for:
- Cracks, impact damage, or liquid intrusion
- A button that is stuck, recessed, loose, or physically obstructed
- Contamination around the button
- Damage to the front overlay or indicator lights
- Evidence that the unit was dropped during the rescue
Press the button only during an approved simulated test when the analyzer and AED indicate that it is safe to do so.
Expected outcome: The button moves normally, returns after release, and has no visible damage.
If the control is physically damaged or remains stuck, stop troubleshooting and remove the AED from service.
6. Check the Electrode Cable Connection
Confirm that the electrode cable connector is fully seated in the AED.
Inspect for:
- A loose or partially inserted connector
- Bent, recessed, contaminated, or damaged contacts
- A cut, crushed, or sharply kinked cable
- Damage where the cable enters the connector
- A “Plug in Cable” prompt
ZOLL directs that the electrode cable remain connected to the AED Plus and identifies checking the cable connection as part of readiness troubleshooting.
Expected outcome: The compatible ZOLL electrode cable is fully connected and no cable prompt occurs.
If reseating the cable corrects the simulated failure and the AED passes all required testing, document the correction and stop.
7. Inspect the Electrode Package and Pads
Verify that the connected electrodes are:
- Compatible with the AED Plus
- Within their expiration date
- Unopened before the reported rescue, unless they were used during that event
- Free from tears, punctures, moisture, or damaged packaging
- Appropriate for the patient category
- Properly adhered during the reported event
For controlled retesting, use an approved defibrillator analyzer and the appropriate test adapter or manufacturer-approved test electrodes. Do not deliver a test shock into unused clinical pads.
Expected outcome: The AED recognizes the connected test interface without electrode or connection warnings.
If replacing a damaged or expired accessory resolves the issue and the unit passes verification, document the result and stop.
8. Check Battery Condition and Battery History
Review whether the AED issued a “Change Batteries” prompt or showed signs of weak power during charging.
Confirm that:
- All ten batteries are the approved type specified for the unit.
- Batteries were installed as a complete matched set.
- Old and new batteries were not mixed.
- Battery contacts are clean and undamaged.
- No corrosion or leakage is present.
- The battery-replacement date is within the facility’s established interval.
ZOLL specifies replacing all ten batteries together and not mixing old batteries with new ones.
Expected outcome: The AED powers normally without battery prompts or abnormal resets.
If battery replacement is required, replace the entire set according to the manufacturer’s instructions. Do not replace only selected cells.
9. Power-Cycle and Perform the Manual Self-Test
With the AED disconnected from any patient:
- Turn the unit off.
- Wait briefly.
- Press and hold the ON/OFF button for more than five seconds to initiate the manual test.
- Listen for the “Unit OK” message.
- Turn the unit off after the test.
- Wait approximately two minutes.
- Confirm that the green check returns and no beeping occurs.
ZOLL recommends removing the unit from service when it repeatedly fails the manual self-test.
Expected outcome: The AED announces “Unit OK,” completes the test, and returns to a green readiness indication.
If the self-test fails, stop and escalate the unit for repair.
10. Test Shock Delivery With an Approved Defibrillator Analyzer
Only qualified Clinical Engineering personnel should perform this step in a controlled bench area.
Using an electrically compatible, calibrated defibrillator analyzer and approved connection method:
- Connect the AED to the analyzer.
- Select a rhythm that the analyzer presents as shockable.
- Allow the AED to complete its analysis.
- Confirm that “Shock Advised” occurs.
- For a semi-automatic unit, verify that the shock button flashes and press it only when prompted.
- For a fully automatic unit, verify the countdown and automatic discharge.
- Confirm that the analyzer detects the delivered shock.
- Verify delivered energy and sequence against the facility’s approved acceptance criteria and current manufacturer documentation.
- Repeat only as required by the approved test procedure.
Do not touch the analyzer connections, AED electrodes, or conductive surfaces while the device is charging or discharging.
Expected outcome: The AED delivers therapy at the correct point in the rescue sequence, the analyzer detects the discharge, and no fault occurs.
If the unit advises a shock but does not discharge into the analyzer, remove it from service. Do not open the enclosure or attempt board-level repair.
11. Confirm Final Readiness
After testing:
- Disconnect the analyzer.
- Install a sealed, compatible, unexpired electrode package.
- Confirm the electrode cable is connected.
- Turn the AED on and verify the expected pad-identification and “Unit OK” prompts.
- Turn the AED off.
- Wait for the green check to return.
- Confirm the AED is not beeping.
- Verify that all required accessories are present.
Expected outcome: The AED passes functional testing and displays normal ready status.
Return the unit to service only when the reported failure has been explained or corrected and all required tests pass.
If the Problem Persists
When the AED advises a shock but cannot deliver therapy during a controlled analyzer test, common external causes have been ruled out. The problem may involve the shock control, charging circuit, discharge circuit, internal connection, or another therapy-related component.
The AED should be:
- Removed from service
- Labeled Out of Service
- Replaced with a verified AED
- Sent for authorized repair or qualified bench evaluation
- Accompanied by rescue-event information and test results when available
Do not disassemble the AED Plus or continue repeated shock attempts. ZOLL warns that internal disassembly presents an electrical-shock hazard and directs servicing to qualified personnel.
Knowing when to stop is proper troubleshooting.
Clinical Use Tip
Never troubleshoot uncertain shock delivery on an active patient. Continue CPR, obtain another verified defibrillator, and move the affected AED to a controlled bench environment before testing.
Work Order Documentation (CCR Method)
CCR = Complaint, Cause, Resolution
Complaint
What was reported by the clinical staff.
Example:
"Clinical staff reported that the ZOLL AED Plus announced “Shock Advised,” but no shock was delivered when the flashing shock button was pressed."
Cause
What was observed during troubleshooting.
Example:
"Bench testing reproduced the failure; the AED recognized a shockable analyzer rhythm and illuminated the shock button, but no discharge was detected despite verified electrodes and a complete new battery set."
Resolution
What action was taken.
Example:
"Removed the AED Plus from service, labeled it Out of Service, provided a replacement AED, and forwarded the unit for authorized therapy-circuit evaluation."
Helpful Details to Include (If Known)
- Semi-automatic or fully automatic version
- Exact voice and display prompts
- Shock-button illumination
- Whether “Release Shock Button” occurred
- Whether “Shock Delivered” was announced
- Readiness-indicator condition
- Beeping or red X observed
- Electrode type, lot, and expiration date
- Electrode cable condition
- Battery type and replacement date
- Manual self-test result
- Analyzer make, model, and calibration status
- Selected test rhythm
- Delivered energy measured
- Event-data retrieval status
- Unusual sounds, heat, odor, or physical damage
- Final device status
Final Thought
A failed AED shock is a high-risk complaint. Protect the patient first, verify the model’s intended sequence, eliminate external accessory and power causes, test with an approved analyzer, and escalate immediately when therapy delivery cannot be confirmed. Complete CCR documentation preserves both patient-safety and repair-history information.
That is successful troubleshooting.