Detcon FP-624D - Manual (Page 38)

Model FP-624D
FP-624D Instruction Manual Rev. 1.2 Page 34 of 42
6. Troubleshooting Guide
Refer to the list of Failsafe Diagnostic features listed in Section 3.6.2 for additional reference in
troubleshooting activities. Listed below are some typical trouble conditions and their probable cause and
resolution path.
Figure 16 Replaceable Combustible Gas Sensor
Sensor Current/Voltage Fault
Probable Cause: Plug-in sensor has failed
Remove plug-in sensor and verify resistance between PIN 5 and PIN 7 and PIN 2 and PIN 4 using an
ohmmeter. At room temperature, the normal reading range should be 2.5-3.5 ohms for both catalytic beads.
Replace plug-in sensor if either measurement is open circuit or significantly out-of range.
Figure 17 Plug-in Sensor (Bottom View)
Zero Fault
Probable Causes: Plug-in sensor has drifted
Perform AutoZero calibration per Section 3.4.1
Replace the plug-in sensor.
AutoSpan Calibration Faults – (Range, Stability, and Clearing)
To clear any AutoSpan Calibration fault, the AutoSpan process must be completed successfully (Section 3.4).
Range Fault
Probable Causes: Failed sensor, cal gas not applied or not applied at appropriate time, or problems with cal
gas and delivery
Check bridge voltage (should be 2.7 +/- 0.2VDC).