Service manual

— Page 73 —
© January 2013 Aqua-Hot
®
600-D01 Series Hydronic Heating System Service Manual - Rev. A
SECTION 9: DIESEL-BURNER COMPONENTS
Flame Sensor:
The flame sensor is a photo resistive device which
supplies the diesel-burner’s controller with a DC
voltage signal when it detects a flame. When the
flame sensor senses the light of the flame, it will
shut the ignition coil off, and send a signal to the
diesel burner controller indicating that everything is
working properly. If the flame sensor does not
sense the flame, it will shut the diesel burner down
in a default after 20 seconds.
The Flame Sensor may fail in two different ways:
1. The Flame Sensor may fail to sense the flame. If
it fails to sense the flame, the burner will fire up
for approx. twenty seconds and then default.
2. The Flame Sensor may also fail, where it already
think there is a flame before there actually is,
which will result in the coil not operating. If
this occurs the burner will not default, and will
continue to spray raw diesel fuel into the
exhaust, until the Diesel Burner Switch is
turned to the OFF position.
Component Test: Ohms
1. In order to perform the following procedures it is
necessary to detach the diesel-burner. Be sure to
review the detaching/attaching instructions in sec-
tion 9.
2. Once the diesel burner has been removed, Locate
and detach the flame sensor’s green and blue wires
from the C-plug harness wires.
3.
Connect the flame sensor’s green and blue wires to
an ohmmeter.
4.
Check resistance by placing a shop rag over the
flame sensor’s glass surface, to simulate a no flame
condition, and then remove the rag and expose to a
light source, to simulate a flame condition.
5.
If the flame sensor is operating properly, the ohm-
meter should register high resistance, over 100K Ω
when the glass surface is covered, and less than 200
Ω when exposed to a light source.
6.
If these resistance numbers cannot be obtained, ver-
ify the flame sensor’s glass surface is clean. If the
flame sensor is clean and the resistance numbers
cannot be obtained, the flame sensor must be re-
placed.
Flame Sensor Maintenance:
1.
For light dirt, dust, and/or carbon deposits, simply
wipe off the flame sensor with a soft cloth.
2.
Should heavy carbon deposits be present, complete-
ly remove the flame sensor from the photo disc and
clean with brake cleaner.
NOTE:
In order to perform the following procedures it is
necessary to detach and reattach the diesel-burner
head. Be sure to review the detaching/attaching
instructions.
NOTE: Be sure to calibrate your ohmmeter prior to check-
ing the flame sensor to proper resistance values.
Flame
Sensor
Green
Wire
Blue
Wire
Figure 49