![background image](http://html1.mh-extra.com/html/l-b-white/guardian-ab100/guardian-ab100_owners-manual-and-instructions_3180946016.webp)
AIR PROVING SWITCH WITH SAIL (FLAPPER)
MODEL AB250
IMPORTANT
On heaters so equipped, make sure you don’t tear or destroy
the foil face fiber gasket located between pilot bracket and
burner casting face. Doing so will cause pilot outages.
Always make sure that if you must remove it for cleaning the
burner area that it is replaced and properly positioned.
1. Shut off the gas supply to heater.
2. Disconnect the heater from its electrical supply.
3. Let the appliance cool down so the pilot assembly is
cool to touch.
4. Loosen the wing screw at the pilot assembly by turning
counterclockwise. It is not necessary to remove the
screw entirely from the pilot assembly. You need to
loosen it just enough to allow you to remove the pilot
shield.
5. When loosened, pull up on the pilot shield, exposing
the pilot bracket, pilot orifice, and thermocouple.
6. Using a soft brush or compressed air, clean the pilot
stack (pop-riveted on inside of pilot shield), of dust
and dirt, paying attention to the throat of the pilot
stack and the flame spreader at the top of the stack.
7. Brush off the top of the pointed pilot orifice making
sure dust and dirt have not plugged orifice hole. If the
orifice must be removed, use the appropriate size
wrench to loosen and remove the compression fitting
and pilot tube from the inlet of the pilot orifice. Use a
wrench to loosen and remove the pilot orifice from the
pilot bracket. Hold the orifice up to the light to see if
the hole in the orifice is clear and open. If not, blow
out with compressed air.
8. To replace the shield and the pilot orifice, reverse
above procedure.
9. Check for gas leaks.
IMPORTANT
The hole in the pilot orifice is drilled to a specific diameter to
match the fuel and gas pressure being used. Do not poke or
push sharp instruments into the hole. Doing so will enlarge
the hole, creating pilot light outage problems. Clean the
orifice only with compressed air, a soft brush, or a dry rag. If
necessary, replace the pilot orifice.
Do not use a pliers to remove the pilot orifice. Pliers will
“round off” the hex head nut on the base of the orifice,
creating difficulty in servicing at a later time. Only use a
wrench of appropriate size.
PILOT LIGHT ASSEMBLY
16
See Fig. 12
BLOWER OUTLET
OF HEATER
AIR PROVING
SWITCH
ARM OF
FLAPPER
AIR PROVING
SWITCH ARM
FAN WHEEL
PIVOT POINT
OF FLAPPER
EDGE OF
FLAPPER
PIVOT POINT
OF FLAPPER
FLAPPER
31.7 MM TO 34.9 MM
1. Shut off the gas supply to the heater.
2. Disconnect the heater from its electrical supply.
3. Make sure there is not any dust, dirt, etc. that may
cause “binding” on the pivot points of the sail as it
rides within the blower housing. If debris is found, use
a soft brush, or compressed air, to clean the area as
necessary.
4. The “arm” of the sail should engage the arm of the
airflow switch when the trailing edge of the sail body is
lifted and is approximately 31.7 mm to 34.9 mm off
the blower housing bottom. At this distance you will
hear a “click” which are the contacts closing within the
switch mechanism. You may also check for continuity
within this circuit.
5. If the switch contacts do not close within this distance,
then manually push in the arm in the switch to make
sure the switch is not defective. If a “click” is heard,
the switch is good and the sail arm then needs to be
adjusted to engage the switch arm.
6. Using a needle nose pliers, gently bend up the arm of
the sail (NOT TTHE S
SWITCH AARM) in increments until
the sail arm engages the switch arm, closing the
contacts of the switch when the sail body trailing edge
is 31.7 mm to 34.9 mm of housing bottom.
FIG. 11