Practice Tips #28: Troubleshooting Sterilizers - Part 2

Unlike the last Practice Tip, part 2 focuses on troubleshooting temperature issues with your sterilizers. Temperature-related problems are very common in sterilizers, so having a lag thermometer helps diagnose these issues.

When experiencing heat-related issues (either low or high) leaving a lag thermometer in the sterilizer for a complete cycle helps to verify the maximum temperature reached. Sometimes it’s just a bad thermometer/temperature gauge on the sterilizer giving an erroneous reading and not a temperature malfunction at all.

PHOTO: 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. They are designed to get hot. Other components control when electricity goes to the heating element(s) and often cause overheating.

Causes of Overheating (In Order of Relative Frequency):

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. Overheated Thermostat. With age, thermostats can get stuck or corroded. Usually you 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.
   

   PHOTO: Pelton & Crane Overheat Thermostat

3. Other Temperature Control Devices. There can be secondary heat sensors, thermistors, etc. that also affect the temperature.
   

   PHOTO: Pelton & Crane Surface Heat Sensor

4. Circuit Board/Controller. Again, use a multimeter to check this component. There may be a potentiometer (variable electronic control) incorporated that can be calibrated as well. Read more about multimeters in Practice Tips #25.
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, 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, check the same components mentioned above 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. It 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. Does the heat light turn on? If the heat light does NOT come on, this indicates current is NOT flowing. This most likely indicates a failed or stuck (overheated) thermostat. As above, you will need a multimeter to check this component.
3. No heat light/indicator? If you do NOT have a heat light/indicator, run through all of the temperature components in order. Start with a visual inspection. Frequently, worn components are identifiable 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. Use a multimeter to check this.

NOTE: Many sterilizers use several heating elements, but some 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. Simultaneous failure of multiple elements is unlikely. However, if your sterilizer takes longer to heat than normal and uses multiple heating elements, a single failed element is very likely. As a first step when encountering any heating issue, identify how many heating elements your sterilizer uses.

When it comes to troubleshooting a temperature issue on your sterilizer, fixing the heating comes down to knowing your heating elements. Some sterilizers use an element that is inside the chamber, while others have a plate or plate(s) on the outside of the chamber. Sometimes the chamber has a layer of insulation wrapped around it, which you need to remove to expose your heating element(s). You can also always call our technical support staff and assist you.