14
TP970 AND TP9600 SERIES PNEUMATIC THERMOSTATS
75-7134—1
TROUBLESHOOTING
See Table 7 for troubleshooting procedures.
Table 7. TP970 Series Thermostat Troubleshooting Procedures.
Problem
Possible Cause
Solution*
Excessive noise
If there is an antihum spring, it is not
touching the throttling plate.
Reposition spring to touch throttling plate.
Stick an adhesive paper dot on the throttling
plate across the hinge between the two rivets
so that the dot is directly below the “A” in MAX
printed on the bimetal.
If there is no antihum spring or cone,
the adhesive paper dot has fallen off of
the throttling plate.
Stick an adhesive paper dot on the throttling
plate as described above.
Air leak in restrictor block and filter
assembly.
Use a bubble solution to locate the leak and
repair it.
Replace the restrictor block assembly and
filter.
Install Stiffener Plate 14004609-001 on the
backplate.
Oil or moisture in lines.
Replace the restrictor block assembly and
filter. Also ensure that the air supply to the
thermostat is dry and clean.
Slow response
Inadequate air flow caused by a
partially clogged restrictor block
assembly and/or filter cartridge.
Replace restrictor block assembly and/or
filter.
Thermostat instability
System gain is too high.
Move throttling range adjustment toward MAX
position and then recalibrate.
Inaccurate readings
Inaccurate calibration.
Recalibrate thermostat.
Metal cover setscrews over-tightened.
Turn setscrews in.
Backplate over-tightened.
Install Stiffener Plate 14004609-001 on the
backplate.
Thermostat not switching
over at changeover pressure
Pressure at thermostat is incorrect.
Readjust compressed airline to proper
switching pressure.
Switchover pressure in thermostat is
incorrectly calibrated.
Turn switchover adjustment screw to
recalibrate pressure for proper switching.
Air leak
Branch line plug leaking.
Install Plug 14002172.
Cannot calibrate thermostat
Oil or moisture in lines.
Replace the restrictor block assembly and
filter. Also ensure that the air supply to the
thermostat is dry and clean.
*If these solutions fail, replace the thermostat.
