If you are having temperature problems with your Pelton Crane autoclave and the heating element and electrical connections are OK, then the problem is probably the thermistor. However, you will only find this particular issue on the OCM, OCR, OCR Plus, and Sentry models, because the others do not have this particular device. If you have one of these models, here is the solution to your temperature problem.
A thermistor sounds scary, but it’s really just a fancy term for a temperature sensor. It looks like a probe and depending on your model you will find it located on the back of the chamber or next to the pressure release valve. It detects temperature changes inside the chamber and sends a signal to the printed circuit board telling it when to turn the unit on and off. The printed circuit board then controls the heat inside the chamber based on its programming.
This little temperature probe doesn’t just turn your autoclave on and off. It sends a signal to the PCB whenever there is any fluctuation in temperature. The thermistor and printed circuit board act as a team to control the temperature inside the chamber and keep it at a constant level.
You’ll know it’s definitely a thermistor problem if:
- Heating elements do not turn on at all (no heat)
- Heating elements turn off too soon (low heat)
- Heating elements won’t turn off at all (uncontrollable heat…temperature keeps rising)
How to Test the Pelton Crane Autoclave Thermistor
Before any autoclave repair can be carried out, you must ensure that you have located the source of the problem. If you have tested your heating elements and found them to be within the acceptable range, and cannot find any other cause for the symptoms your autoclave is exhibiting…this is the next part to test.
Don’t worry. Testing the thermistor is easy. All you will need is an ohmmeter.
Locate the thermistor in your autoclave and trace the two black wires to the PC board. You will find that these wires are connected to the board with a modular plug or the connection is hardwired (soldered). All you need to do is test those connections.
To test, simply insert a probe into each of the two plug openings (or into each wire where they connect to the solder). Either way, it doesn’t matter what color probe goes where for this test.
Note: The thermistor is very sensitive to heat and it is important that it be at room temperature (~72 degrees) when performing this test.
Your reading on your ohm meter should be close to 1 meg ohm. If not, the thermistor is defective and will need to be replaced.
Then, if you get a reasonable reading on the thermistor (allowing for temperature conditions), have someone take a rag soaked in hot water and wrap it around the probe inside the chamber, while you watch the readings on your meter. .
You should instantly notice a substantial drop in resistance reading. This tells you that it is working. That is, the thermistor is responding to the temperature change. If you don’t see this answer, then you know you need to replace it. And believe it or not, as simple as it has been up to this point… the testing you’ve already done here is more complex and difficult than the repair will ever be.
To repair your autoclave, simply remove the wires from the board and, using a wrench, unscrew the thermistor from the chamber and install a new one…then reconnect the wire.
You’re done! And you’ve just saved yourself potentially thousands of dollars in repair bills and lost billing.