Schwank P40U Owner's Manual page 29

SERVICE CHECKS
Flame current passes through the flame from the
sensor to ground. The minimum flame current
necessary to keep the system from lockout is 0.7
microamps. To measure flame current, connect
an analog DC microammeter to the FC- FC+ ter-
minals per figure at right.
Meter should read 0.7 µA or higher. If the meter
reads below "0" on scale, meter leads are re-
versed. Disconnect power and reconnect meter
leads for proper polarity.
TROUBLESHOOTING - FENWAL DSI
(also see Heater Troubleshooting Page 33)
SYMPTOM
1. Dead
2. Thermostat on
- no blower output
3. Pressure switch input okay,
but no Trial-for-Ignition
after purge delay
4. Valve on, no spark
5. Spark on, no valve
6. Flame ok during TFI, no
flame sense (after TFI)
Multipurpose Meter
RECOMMENDED ACTION(S)
A. Miswired - check electrical supply (120Vac ± 5%)
B. Transformer bad (24Vac ± 10%)
C. Fuse/Circuit breaker bad
D. Bad control (check LED for steady on)
A. Miswired
B. Bad thermostat no voltage @ terminal W
C. Bad control (check LED for steady on)
A. Miswired (check PSW terminal voltage: 24Vac ± 10%)
B. Flame sense problem (existing flame: check LED - 2
flashes)
C. Bad control (check line voltage between L1 & IND)
A. Shorted electrode
B. Open HV cable
C. Bad control
A. Valve coil open
B. Open valve wire
C. Bad control (check 24Vac voltage between V1 & V2)
A. Bad electrode
B. Bad HV igniter wire
C. Poor ground at burner
D. Poor flame (check flame current)
29
Use Microamp
scale
P40U-F / P40U-IF I&O Manual
IM101220
RD: MAR 2014
RL: 4B