ECA 450 MaintenanceInstruction 0024-9400 674.4.3 HC Sensor ReplacementUnlike the other sensors that are held in place by their associated bayonetholders, the HC sensor is plugged into its printed circuit board which, inturn, is secured inside the sensor compartment with four screws. Remove thisboard and replace the sensor as follows:Material Required:• Medium Phillips screwdriver• Small flat blade screwdriver• Replacement HC sensor (refer to Section 6.1)Procedure:1. Gain access to sensor compartment by first removing two screws from thesensor-cover plate, and then removing plate (see Figure 4-3).2. Unplug the HC sensor’s printed circuit board from its connector jack.3. Remove the sensor’s printed circuit board by first removing the board’sfour corner screws, and then lifting the board with the HC sensorattached out from the sensor compartment.4. Unplug old sensor and discard.5. Remove replacement sensor from its plastic canister; then plug sensorinto its printed circuit board.6. Install and secure the HC sensor’s circuit board inside the sensorcompartment using the screws removed in Step 3.7. Install sensor-cover plate that was removed in Step 1.8. Place analyzer in an area of fresh air and turn it ON. After the warm-upcycle completes, observe that no sensor error messages should haveappeared.9. Calibrate the new sensor per Section 3.
