Fyrite Pro 125 Sensor and Internal Filter Replacement

When it is necessary to replace the Oxygen, Carbon Monoxide Sensor or internal filter in the Pro 125, read the manual and follow the steps below.

Do remember that when the Carbon Monoxide sensor is replaced, it is absolutely necessary to calibrate the sensor.  To read about calibrating the CO sensor in a Fyrite Pro, click here.

When an Oxygen sensor is replaced, no calibration is necessary as the instrument does an 'automatic' power up of the Oxygen sensor during the 60 second warm up period each time the instrument is turned on.  This means that the sensor is 'assuming' the oxygen content in the air is 20.9%.

The internal filter provides protection to the pump and may need to be replaced depending on the type use the instrument gets.

To access the internal components, remove the strap and batteries.  You will find 4 phillips head screws, one at the bottom of the battery compartment and three more in the other corners of the instrument.

Remove the 4 screws, flip the instrument back over and gently remove the front of the case.

Disconnect the three plugs - two red and one white from the circuit board.

Lay the circuit board back to expose the sensors and filter assembly.

The CO sensor is here:

The Oxygen sensor is here:

And the internal filter is here:

Carbon Monoxide Sensor Replacement (Fyrite Pro 100, 120, 125)

The CO sensor plugs into the bottom of the board.  To replace it, simply unplug the old sensor and install the new one.  You will notice a guide which allows the sensor to be plugged in only one position.  Again, remember that any time a CO sensor is replaced, the sensor needs to be calibrated.  To read about calibrating the CO sensor in a Fyrite Pro, click here.

Oxygen Sensor Replacement (Fyrite Pro 120, 125)

To replace the Oxygen sensor, remove the old sensor from the bayonet type socket.

Make certain that when the Oxygen sensor is removed, the old gasket comes out as well.  When you get the new sensor, a new gasket will be provided.

The gasket has a peel off backing which has to be removed and the gasket applied to the sensor.

Note:  Often, a new Oxygen sensor has to stabilize once it has been installed.  When a new sensor has been installed and the instrument reassembled and turned on, an 'Oxygen Sensor Error' message may be displayed after the 60 second warm up period.  Should this occur, turn the instrument off and try it again in a couple of hours.  Generally, 3 to 4 hours is sufficient, occasionally it takes overnight.

Internal Filter Replacement (Fyrite Pro 100, 120, 125)

An easy way to tell if the internal filter is plugged is to listen to the sound of the pump with the hose and probe assembly removed.  Put your finger over the 'GAS' port on the bottom of the instrument.  If you hear the pump motor 'bog' down, the filter is probably clear.  If you don't hear any change in the pitch of the pump motor, the filter probably needs cleaning.

To change out the filter, unscrew the two halves.  The 'male' half is the part containing the filter screen,  Remove this half from the tubing and replace.

Reassemble the instrument in the reverse order.