SERVICING
43
S-314 CHECKING FLAME SENSOR
A flame sensing device is used in conjunction with the ignition
control module to prove combustion. If proof of flame is not
present the control will de-energize the gas valve and “retry”
for ignition or lockout.
The following drawings illustrate from a bottom view, the
approximate distances for the ignitor and flame sensor to the
gas inshot burner. You will note they are in the main burner
stream, not in the carry over ports as shown in the following
figure.
Flame Sensor
Models with Integrated Ignition
Control & Flame Sensor Probe
(80% Upflow Model Shown, Counterflow Similar)
WARNING
HIGH
VOLTAGE
D
I
S
CONNECT
ALL
POWE
R
BEFO
R
E
S
E
R
VICING
O
R
IN
S
TALLING
THI
S
UNIT.
M
ULTIPLE
POWE
R S
OU
R
CE
S
MAY
BE
P
R
E
S
ENT.
F
AILU
R
E
TO
DO
S
O
MAY
CAU
S
E
P
R
OPE
R
TY
DAMAGE,
PE
RS
ONAL
IN
J
U
R
Y
O
R
DEATH.
1. Disconnect the orange flame sensor wire from the sensor
.
2. Connect a micro-amp meter in series with this wire and
the sensor terminal.
3. Place the unit into a heating cycle.
L
INE
VOLTAGE
NOW
P
R
E
S
ENT
WARNING
4. As soon as flame is established a micro-amp reading
should be evident once proof of flame (micro-amp
reading) is established, the hot surface ignitor will be de-
energized.
5. The Integrated Ignition controls will have 1 to 4 micro-
amps. If the micro-amp reading is less than the minimum
specified, check for high resistance wiring connections,
sensor to burner gap, dirty flame sensor, or poor
grounding.
6. If absolutely no reading, check for continuity on all
components and if good - replace ignition control module.
NOTE:
Contaminated fuel or combustion air can create a
nearly invisible coating on the flame sensor. This coating
works as an insulator causing a loss in the flame sense signal.
If this situation occurs the flame sensor must be cleaned with
steel wool.
