Data Sheet for Product

Technical Instructions
Document Number 155-065P25
February 7, 2022
Page 10 Siemens Industry, Inc.
Table 3. Troubleshooting Guide.
Problem
Check
Cause
Action
Control pressure
stays at
approximately zero
Air supply
Low supply pressure
As required
Nozzle or flapper
Dirt on nozzle or
flapper
Clean nozzle or
replace thermostat
Restrictor
Clogged restrictor
Replace restrictor
Calibration
Out of calibration
Recalibrate
Control pressure
stays at
approximately
supply pressure
Nozzle
Clogged nozzle
Clean nozzle or
replace thermostat
Calibration
Dirt on either supply or
exhaust valve seat
Alternately close and
open nozzle by gently
pushing down the
bimetal
Excessive air
leakage from
exhaust port on left
side of thermostat
Supply and return
line connection
Connections are
interchanged or
connection to port is
incorrect
As required
Chassis Tube Connector
and Restrictor Plate
Replacement
1. Remove thermostat chassis from wall. Terminal does not have a ball check valve.
NOTE: You must close off the supply air. For example, use a connector with the supply
air terminal plugged.
2. Remove two Phillips head screws from connector on back of thermostat chassis. Pull
connector out of recess. If necessary, pry connector loose with a screw driver, but be
careful not to damage restrictor plate and gasket.
3. Remove gasket from under connector. Remove restrictor. Remove second gasket
from under restrictor.
4. Use restrictor replacement kit 192-321 to replace gasket, restrictor, and second
gasket.
NOTE: The restrictor plate is keyed to ensure proper orientation during installation.
5. Remove filters from existing connector and insert in new connector. Or, if filters are
dirty, use restrictor replacement kit 192-321 to replace filters.
6. Use chassis tube connector replacement kit 192-525 to replace connector and
mounting screws.