Practice Tips #28: Troubleshooting Sterilizers- Part 2

Temperature-related problems are very common in sterilizers. A lag thermometer will help diagnose heating related issues. When experiencing heat-related issues (either low or high) leaving a lag thermometer in the sterilizer for a complete cycle will verify the maximum temperature achieved during that cycle. Sometimes it’s just a bad thermometer/temperature gauge on the sterilizer giving an erroneous reading and not a temperature malfunction at all.

Lag Thermometer #RP-113

Excessive (High) Temperature

Excessive temperature can damage your delicate and expensive equipment and is more frequently encountered than many might expect. Heating elements are almost NEVER the cause of excessive temperature. Heating elements are designed to get hot when power is supplied to them. Other components control when electricity goes to the heating element(s) and would be the cause of overheating. In order of relative frequency/likelihood, the following can cause overheating:

  1. Low water- running dry can increase the heat in the chamber. Check water level as shown in our previous issue: Trouble Shooting Sterilizers- Part 1, under “Poor or No Water Flow”.
  2. Overheat thermostat- with age thermostats can get stuck or corroded. Usually you will need to verify resistance with a multimeter. Call our techs for the specs of your make and model. Some overheat thermostats are simple hydraulic thermostats and a visual inspection may give an indication of a stuck condition.


    Pelton & Crane Overheat Thermostat

  3. Other temperature control devices- there can be secondary heat sensors, thermistors, etc. that will also affect the temperature.


    Pelton & Crane Surface Heat Sensor

  4. Circuit board/controller- again a multimeter will normally be needed to check this component. There may be a potentiometer (variable electronic control) incorporated that can be calibrated as well.
  5. Electrical short- look for signs of scorching on any of the wiring and loose or frayed wires, including those on the heating element(s)

Note: To check the electrical components listed above in 2-5, you will generally check for continuity or resistance values. Call our technical support staff with your make and model of sterilizer for what readings you should find.

Low (or No) Heat

While excessive temperature is not normally attributed to the heating element, low (or no) heat can be the result of a failed heating element. However, the same components are involved as above and should be checked as well.

  1. Does your sterilizer incorporate a heat light of some sort? The heat light indicates that current should be flowing to the heating element and makes it more likely that the problem is in the element itself if the heat light is illuminated. Once again, a simple visual inspection of the element may indicate the condition of the element. If the element checks out, then check the controller/circuit board.
  2. If the heat light does not come on, this indicates current is not flowing, most likely due to a failed or stuck (overheat) thermostat. As above, you will need a multimeter to check this component.
  3. If you do not have a heat light/indicator you will simply need to run through all of the temperature components in order. It’s best to begin with a visual inspection. Frequently, worn components can be identified on sight. If nothing is apparent, then check all of the temperature related components in the order listed above for OVERHEATING, adding the heating element(s) to the end of the list. The heating element will have resistance values specific to your make and model of sterilizer. You will need a multimeter to check this (see our issue of Practice Tips on Multimeters for more information on how to use this helpful tool).

Note: we reference heating element(s) above. Many sterilizers use several heating elements but some will only have one. If your sterilizer has multiple elements and fails to heat at all, this further reduces the likelihood of a failed element being at the root of the problem (as simultaneous failure of multiple elements is unlikely). However, if your sterilizer is taking much longer to heat than normal and uses multiple heating elements, a single failed element is very likely. It’s a good first step when encountering any heating issue to simply identify how many heating elements your sterilizer uses.

One more note on heating elements- some sterilizers will use an element that is inside the chamber, while others will have a plate or plate(s) on the outside of the chamber. Sometimes there is a layer of insulation wrapped around the chamber which you will need to remove to expose your heating element(s). You can also always call our Tech support staff and we can advise how many elements you should have as well as their location based on your make and model of sterilizer.


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