Instruction Manual
D200126X012
2502 Controllers
June 2017
24
Table 4. Troubleshooting Chart for Fisher 2502 Controllers (continued)
Fault
Possible Cause
Check
Correction
2. Controller controlling off setpoint
or switching point.
2.1 Supply pressure not set
correctly.
2.1 Make sure regulator supply
pressure is set correctly. Make sure
regulator IN supply pressure is within
limits.
2.1 Reset the supply regulator
pressure. If the condition occurs
again, rebuild or replace regulator.
Provide a regulator input pressure
within regulator limits.
2.2 Leak in the controller loop.
2.2 Use soap and water to check for
internal and external leaks.
2.2 Replace or repair leaking parts
as necessary.
2.3 Leaking displacer.
2.3 Insure the displacer is not filling
with process fluid.
2.3 Refer to sensor maintenance
procedures in the appropriate sensor
instruction manual.
2.4 Flapper adjustment.
2.4 Insure the flapper is not loose on
the torque tube shaft and is
centered on the nozzle.
2.4 Replace or tighten flapper
assembly as necessary and/or center
flapper on nozzle.
2.5 Process variable changed.
2.5 Insure the process variable has
not changed from original
calibration settings or, displacer not
design specific gravity of process.
2.5 Change process variable back to
original specification or recalibrate.
If necessary, provide replacement
displacer of correct size and
recalibrate.
3. Controller cannot attain full
output range.
3.1 Supply pressure not set
correctly.
3.1 Make sure supply pressure is set
correctly. Make sure regulator IN
supply pressure is within limits.
3.1 Reset the regulator pressure. If
problem reoccurs, replace or rebuild
the regulator. Insure regulator IN
supply pressure is within limits at all
operating levels.
3.2 Flapper adjustment.
3.2 Insure the flapper is not loose on
the torque tube shaft and is
centered on the nozzle.
3.2 Replace or tighten flapper
assembly as necessary and/or center
flapper on nozzle.
3.3 Process variable changed.
3.3 Insure the process variable has
not changed from original
calibration settings or, from
displacer design specific gravity.
3.3 Change process variable back to
original specification or recalibrate.
If necessary, provide replacement
displacer of correct size and
recalibrate.
3.4 Relay malfunction.
3.4 Check for relay malfunction by
using the testing relay deadband
procedure.
3.4 Depress plunger to clean out the
fixed restriction. Replace relay using
the procedure in the Maintenance
section.
3.5 Leaking controller loop.
3.5 Use soap and water to check for
internal and external leaks.
3.5 Replace or repair leaking parts as
necessary.
4. Controller remains at full or zero
output pressure.
4.1 Supply or output pressure gauge
malfunction
4.1 Insure the pressure gauges are
registering correctly.
4.1 Replace pressure gauges. Use
corrective action given in section 3
of this table.
4.2 Flapper adjustment.
4.2 Insure the flapper is not loose on
the torque tube shaft. Insure the
flapper is centered on the nozzle.
4.2 Replace or tighten flapper
assembly as necessary and/or center
flapper on nozzle.
Removing Controller from Sensor
WARNING
To avoid personal injury in the following steps, turn off the supply pressure and carefully release any pressure trapped in
the controller before breaking any pressure connection. Provide a bypass for the control device if continuous operation is
required during maintenance.
Refer to figure 14 for key number locations, unless otherwise indicated.
1. Disconnect the supply and output pressure tubing from the controller.
2. Loosen the hex nut (key 40) that secures the operating arm base or pointer assembly (key 68 or 51) to the torque
tube rotary shaft. Do not lose the two link bearings (key 87, not shown).
