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LAARS HEATING SYSTEMS
NORMAL SEQUENCE
EVENT
CONTROL FUNCTION
VERIFIED
LIGHT CONFIRMS EVENT
A. Power switch on.
Integrated boiler control
(S9301A).
Green "POWER" light on.
Note: If internal pump is
running unit may be in
lockout. Reset power
switch.
B. Pre-purge low limit
aquastat or thermostat
calling (2-17 secs).
1. Internal pump starts.
Red "PURGE" light on
NOTE: If unit is in purge
mode without light, stack
switch is not proving air
flow.
2. Low limit (HW-only),
operating control, safety
limit, system or
differential pressure
switch, stack switch.
3. Blower starts.
C. Ignitor heats up and
remains on (17-39
secs).
Ignitor via S9301A.
Red "IGNITOR" light on.
Red "PURGE" light off.
Blower continues to run.
D. Gas valve
energized (37-43
secs).
Gas valve opens.
Red "VALVE/FLAME" light
on.
E. Ignitor off (39 sec)
Gas valve energized
(39 - 43+ sec).
Ignitor, air & gas source. Ignitor monitors flame via
flame rectification to ground
(0.6 - 1.0 microamps).
Quick Reference Trouble Shooter
S9301A Control Module
FAILURE TO COMPLETE EVENT CYCLE
NO LIGHT OR
BLINKING LIGHT
ACTION FOR DIAGNOSIS
1. No. 120 VAC supply.
1. Read voltage betwen black & white
wires at back of (120 VAC) plug.
2. Defective 24 VAC
transformer (Check 3
AMP inline fuse).
2. Read voltage between yellow wires at
back of (VAC 24XFMR) plug.
3. Defective S9301A
module.
3 Replace S9301A module
part #2400-224.
1. Internal pump
defective or air bound.
1. Check for 120 VAC at module pins
marked "CIRCULATOR" (opposite
brown & white).
2. Defective low limit,
operating control, safety
limit, or system
differential pressure
switch.
2. Jump control wires, one control at a
time to identify open circuit in control (no
continuity) FOR DIAGNOSIS ONLY.
3. Defective inducer
(blower).
3. Check for 120 VAC at module pins
marked "INDUCER" (opposite gray and
white wires).
Ignitor does not heat up -
look for heat up at ignitor
base.
Check for 120 VAC at pins marked
IGNR (blue wires) during "IGNITOR"
light "ON".
1. Stack switch does not
confirm air flow.
2. Gas valve has short.
Check for 24 VAC between orange and
yellow wires on gas valve when red
"VALVE/FLAME" light is on.
Unit transfers to purge
12-15 seconds after
valve/flame light on and
repeats sequence.
See trouble shooting section under
"cross contamination" and "short
cycling" in service manual.
