Detcon FP-624D-HT - Manual (Page 39)

Model FP-624D-HT
FP-624D-HT Instruction Manual Rev. 1.1 Page 35 of 44
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 15 Replaceable High Temperature Combustible Gas Sensor
Sensor Current/Voltage Fault
Probable Causes: Open Sensor – broken wire or contact in sensor
Remove sensor and check red wire against green wire, then blue wire against green wire. Normal reading is 1-
4 ohms and failed reading is an open circuit.
Replace sensor if verified as Open Sensor
Zero Fault
Probable Causes: Sensor has drifted
Perform AutoZero calibration per Section 3.4.1
Replace the High Temperature 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).
Check validity of span gas and flow rate (check MFG date on cal cylinder).
Make sure correct cal factor is set
Check for obstructions through stainless steel sinter element (including being wet).
Replace the plug-in sensor.
Stability Fault
Probable Causes: Failed sensor, empty or close to empty cal gas cylinder, or problems w/ cal gas and delivery
Check bridge voltage (should be 2.7 +/- 0.2VDC).
Check validity of span gas and flow rate (check MFG date on cal cylinder).
Make sure correct cal factor is set
Check for obstructions through stainless steel sinter element (including being wet).
Replace the plug-in sensor.
Clearing Fault