DIY OCXO Thermistor

If the temperature control on your oven does not seem to be responding it may be because the thermistor has shorted out. A thermistor is an electronic component that functions as a variable resistor. The thermistor senses and responds to changes or fluctuations in heat. An oven controlled crystal oscillator, or OCXO, is a thermistor used for heat control inside ovens. The OCXO is mounted inside the metal shell of the oven. Installing an OCXO thermistor takes approximately one to two hours.

Things You'll Need

• Screwdriver
• Soldering iron
• Needle-nose pliers
• Solder

Instructions

1. Shut off the power to the oven from the breaker box circuit.

2. Consult the oven owner's manual to identify the exact location of the thermistor, as they may be located in different spots from model to model. Most, however, are mounted on a small circuit board located on the back side of the oven.

3. Open the oven door and remove the mounting screws with a Phillips screwdriver. Set the screws aside in a safe place and then slide the oven out from the wall if the oven is a wall-mounted unit. If it a freestanding oven-stove combination, slide the whole unit from the wall and then remove the back panel screws in each corner to access the oven's inside.

4. Plug the soldering iron in. Place the tip of the iron to the old thermistor's solder connections and melt it. If the soldering is equipped with a solder sucking ball, use it to suck the old solder off the circuit. If it is not, use a moist sponge to wipe the old solder off.

5. Pull the old thermistor from the circuit board with the needle-nose pliers.

6. Insert the leads of the new OCXO thermistor into the circuit board terminals.

7. Hold the solder just above the thermistor wire lead and place the tip of the soldering iron against it to melt a dab of solder onto the connection. Repeat to solder the other thermistor lead.

8. Replace the back panel of the oven with a screwdriver if the oven is a free-standing unit. If not, slide it back into the wall and insert the mounting screws. Tighten the mounting screws with the screwdriver.

9. Restore power to the oven at the breaker box by flipping the circuit switch.

References

• Oven and Stove Repair; Daniel Gates