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Instruction Manual
IM-106-880, Rev 1.0
January 2007
7-3
OCX 8800
FAULT ISOLATION Faults in the OCX 8800 Transmitter are indicated by messages displayed on
the HART communicator. Fault indications that can appear are listed in
Table 7-1, Troubleshooting.
If a fault is indicated on the HART communicator, locate the fault indication in
Table 7-1. For each fault listed, there are related Probable Causes and
Recommended Corrective Actions. The Probable Causes are listed in the
order of most probable to least probable. Starting with the most probable
cause, inspect and test the unit to isolate the actual cause, then use the
Recommended Corrective Action listed to correct the problem.
Table 7-1. Troubleshooting
O2 Sensor R High (Oxygen sensor resistance high, > 5000 Ohms)
O2 Sensor Open (Oxygen sensor disconnected)
Probable Cause Recommended Corrective Action
Loose or open O
2
cell circuit connection Check O
2
cell circuit wires for breaks or loose connections. Repair lead wire break or
loose connections.
O
2
cell degraded or failed Check O
2
cell impedance by reading the O2 Snsr R value via HART (see Figure 4-3,
sheet 2). If cell impedance is zero, replace O
2
cell with cell replacement kit. If cell
impedance is less than 5000 ohms, check for cell housing ground fault. Repair ground
fault. If cell impedance is greater than 5000 ohms and no ground fault is indicated,
replace O
2
cell with cell replacement kit.
Ref Current Err (RTD excitation current error)
Probable Cause Recommended Corrective Action
Loose or open lead or circuit wire connection for
COe sensor or CJC sensor current loop
Check all COe and CJC sensor current loop wiring per Figure 7-3 and Figure 6-7.
Correct wiring faults.
COe sensor grounded Check resistance of COe sensor leads to ground per Figure 6-7. Replace COe sensor if
resistance is less than 10M Ohms.
COe sensor failed Check resistance of both COe sensor elements per Figure 6-7. Replace COe sensor if
resistance of sensor element is not between 100 and 250 Ohms.
CJC sensor grounded Check resistance of CJC sensor to ground per Figure 6-7. Replace CJC sensor if
resistance is less than 10M Ohms.
CJC sensor failed Check resistance of CJC sensor per Figure 6-7. Replace CJC sensor if resistance of
sensor is not between 100 and 150 Ohms.
O2 Temp Hi (Oxygen sensor heater temperature high, > 750ºC)
Probable Cause Recommended Corrective Action
High noise in OCX power supply Check power supply for line noise or voltage fluctuations. Install power line filter kit
(PN 6A00171G01) or high quality line filter for input power.
COe Temp Hi (Combustion sensor heater temperature high, 310ºC)
Probable Cause Recommended Corrective Action
High noise in OCX power supply Check power supply for line noise or voltage fluctuations. Install power line filter kit
(PN 6A00171G01) or high quality line filter for input power.
Table continued on next page