Autoclave Troubleshooting: What to Check, and When to Stop
A symptom-by-symptom guide to the faults clinic autoclaves show most often — what staff can safely check, and when the machine must come out of use until an engineer has seen it.
First rule: what goes into quarantine
A fault on a sterilising cycle is a patient-safety question before it is a repair question. Until the cause is found, treat the load as not sterile.
- Do not release any load from a cycle that aborted, failed or printed values outside its limits. Reprocess it once the machine passes its tests.
- After a failed Bowie-Dick, helix or vacuum leak test, run no patient loads until a repeat test passes — and if it fails twice, until an engineer has repaired the machine.
- Write down the error code or message, the cycle number and what was in the load before you switch anything off.
- Never open the panels, bypass a sensor or force the door. Steam and hot water under pressure cause serious burns.
Read next What your SOP should say about failures
Wet packs
Packs that come out damp — droplets inside the pouch, or water pooled on the tray — are not treated as sterile, because moisture can carry microorganisms through paper. Work through these checks in order.
| Check | What to look for | What to do |
|---|---|---|
| Load | Overfilled trays, pouches stacked flat on each other, heavy cassettes | Load less; place pouches in a single layer or on edge in a rack, as the manual shows |
| Cycle | Door opened before drying finished; a fast cycle used for a full load | Let the cycle finish; use the full cycle for full loads |
| Instruments | Instruments pouched while still wet from rinsing | Dry them fully before packing |
| Water | Poor-quality water, or scale in the steam generator | Use water of the specified quality; drain and refill the reservoir |
| Filters | Blocked chamber drain filter or bacteria filter | Clean the drain filter; the bacteria filter is replaced at service |
| Handling | Hot packs set on a cold metal bench or in an air-conditioning draught | Let packs cool on the tray or a rack before storing them |
| Machine | Wet packs continue after all of the above | A weak vacuum pump, valve or heater fault — call the engineer |
Read next How to load an autoclave
Failed vacuum, leak or Bowie-Dick test
Vacuum leak test fails
The chamber cannot hold vacuum. Most often the door seal or the chamber rim is dirty, cracked or worn. Clean both with a damp lint-free cloth and repeat the test under the conditions the manual sets — many require a cold, empty, dry chamber. A second failure usually means a worn seal or a leaking valve.
Bowie-Dick or helix test fails
Air is not being removed, or steam is not reaching the centre of the load. Before blaming the machine, check that the test was in date, placed where the manual says and run in an otherwise empty chamber after warm-up. If a correctly run repeat still fails, stop using the machine for patient loads.
Spore test positive
Treat it as a sterilisation failure until proved otherwise. Stop using the steriliser, repeat the test, review the cycle records since the last negative result and recall loads as your policy requires.
Read next How the tests workUjian autoclave (Bahasa Malaysia)
Door will not open, or will not lock
- Locked after a normal cycle: most autoclaves keep the door locked until chamber pressure is back to atmospheric and the temperature has dropped. Wait for the end-of-cycle signal.
- Locked after a power cut or aborted cycle: restore power and let the machine finish its own venting routine. Use a manual release only if the manual describes one, and only when the chamber is cool and unpressurised.
- Will not close or lock: look for a pouch, tray edge or debris caught on the seal, and check the seal is seated in its groove.
- Steam or water escaping round the door: let the cycle end, clean the seal and rim, and have the seal replaced if it is damaged. Do not release that load.
Aborted cycles and error messages
Error codes are specific to each make and model, so the manual is the reference. Most fall into a few groups.
| Error group | Common causes | What staff can check |
|---|---|---|
| Low water or water quality | Empty reservoir, wrong water, conductivity too high | Refill with the specified water; drain and refill after a quality warning |
| Used-water tank full | Tank not emptied, drain hose kinked | Empty the tank and straighten the hose |
| Vacuum not reached | Door seal leak, blocked filter, pump wear | Clean the seal, rim and drain filter, then retest |
| Temperature or pressure out of range | Overloading, sensor drift, heater or valve fault | Reduce the load and repeat once; if it recurs, call the engineer |
| Door or lock error | Door not fully closed, lock switch fault | Reseat the door and check nothing is trapped |
| Power interruption | Power cut or tripped breaker mid-cycle | Reprocess the load; ask an electrician about the circuit if it recurs |
Stained or spotted instruments
Most stains come from the water or the cleaning stage rather than the steriliser itself.
| What you see | Usual cause |
|---|---|
| White or grey spots or film | Minerals from the final rinse water or the autoclave reservoir |
| Brown or rust spots | Rust from damaged or non-stainless instruments in the same load, or from rust in the water |
| Rainbow or blue-gold discolouration | An oxide layer, often linked to detergent residue or repeated heating; usually cosmetic, but review your detergent and rinse |
| Pitting — small dark holes | Chlorides from saline, dried blood or bleach; withdraw instruments that are pitted |
| Dull film over the whole load | Residue in the chamber or poor water; clean the chamber and check water quality |
Read next Cleaning before sterilisationAutoclave water quality
Before you call the engineer — and after
- Have the model, serial number and software version ready, with the error code and the cycle printout.
- Note the recent test results, and anything that changed: a new water source, new pouches, a new staff member or a recent move.
- Photograph the door seal, any leaks and any stained instruments.
- After the repair, run the air-removal and leak tests, and a spore test if the repair could affect the cycle, before releasing patient loads.
- Keep the engineer’s written report with your maintenance records.
Read next Maintenance checklistServis autoclave (Bahasa Malaysia)
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