If you’re having temperature problems with your Pelton Crane autoclave and the heating element and electrical connections all check out fine, then the problem is probably the thermistor. You’ll only find this particular problem in the OCM, OCR, OCR Plus and Sentry models, though, because the others don’t have this particular device. If you have one of these models, then here’s the solution to your temperature trouble.
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’ll either find it located at the rear of the chamber or next to the pressure release valve. It senses temperature changes inside the chamber and sends a signal to the pc board telling it when to turn the unit on and off. The pc 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 pc board every time there’s any fluctuation in temperature. The thermistor and pc 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:
- The heating elements are not turning on at all (no heat)
- The heating elements are turning off too soon (low heat)
- The heating elements are not turning off at all (uncontrollable heat….temperature keeps rising)
How To Test The Pelton Crane Autoclave Thermistor
Before any autoclave repair can be accomplished, you want to be sure 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 no other cause can be found for the symptoms your autoclave is exhibiting….this is the next part to test.
Don’t worry. Testing the thermistor is easy. All you’ll need is an ohm meter.
Locate the thermistor on your autoclave and trace the two black wires back to the pc board. You’ll find that these wires are connected to the board with either 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 openings on the plug (or each wire where they connect to the solder. Either way, it does not matter which color probe goes where for this test
Note: The Thermistor is intensely sensitive to heat and it’s important that it be at room temperature (~72 degrees) when conducting this test.
Your reading on your ohm meter should be close to 1 meg ohms. If not, the thermistor is defective and will need to be replaced.
Next, 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 observe the readings on your meter.
You should instantly notice a substantial drop in the resistance reading. This tells you it’s working. That is, the thermistor is responding to the changing temperature. If you don’t see this response, then you know you need to replace it. And believe it or not, as simple as it has been to this point….. the testing you have already done here is more complex and difficult then the repair will be.
To repair your autoclave, simply remove the wires from the board and using a wrench, unscrew the thermistor from the chamber & install the new one…… then reconnect the wire.
You’re done! And you’ve just saved yourself potentially thousands of dollars in repair bills and lost billings.