Troubleshooting Guide - Schwank P40U Owner's Manual

24. TROUBLESHOOTING GUIDE — HEATER OPERATION — FENWAL DSI
WARNING
SEQUENCE OF EVENTS (also see DSI Troubleshooting previous page)
APPLY 120 VOLTS - GREEN LIGHT
SET THERMOSTAT TO CALL FOR
COMBUSTION AIR BLOWER
YES
AIR PROVING SWITCH HAS
CLOSED 24 VOLTS IS PRESENT
AT "PSW" AT DSI CONTROL.
YES
BLOCKED FLUE SWITCH IS
CLOSED
24 VOLTS IS PRESENT AT "TH" AT
YES
SPARK IGNITER / SENSOR
YES
24V TO GAS VALVE - RED LIGHT
CONTINUED
Improper adjustment, alteration, service or maintenance can
cause property damage, injury or death. This heater must be
installed and serviced only by a trained gas service technician
NO

REMEDY 120 VOLTS SUPPLY FAULT

CHECK 120V TO DSI AT "L1"
NO

CHECK 120V OUT AT "IND" FROM DSI TO
NO

FAULTY RELAY SWITCH IN DSI — RE-
PLACE DSI

CHECK TUBING TO SWITCH IS CON-
NO
NECTED AND NOT BLOCKED OR KINKED

CHECK AIR PRESSURE WITH MANOME-
TER

CHECK FOR OBSTRUCTION IN THE AIR
INTAKE

CHECK TUBING TO SWITCH IS CON-
NO
NECTED AND NOT BLOCKED OR KINKED

CHECK AIR PRESSURE WITH MANOME-
TER

CHECK INTEGRITY OF SWITCH
NO

CHECK DSI CONTROL FUSE FOR CONTI-
NUITY

VISIBLY CHECK IF IGNITER IS SHORTING
OUT

CHECK GROUND WIRING

REMOVE AND INSPECT IGNITER AND
LEAD

CHECK BOOT OF THE IGNITION CABLE
FOR SIGNS OF MELTING OR OVERHEAT-
ING

IF "YES" ... TAKE PROTECTIVE ACTION TO
SHIELD CABLE AND BOOT FROM EXCES-
SIVE TEMPERATURE; REPLACE ANY DE-
FECTIVE COMPONENT
35

REPLACE DEFECTIVE SWITCH
P40U-F / P40U-IF I&O Manual
IM101220
RD: MAR 2014
RL: 4B