1. Is power available in wall outlet?
MONITOR 441 HEATER
GENERAL CHECKS
Is power available in wall outlet?
Is power plug inserted in wall outlet?
Has there been a power interruption?
(Display window shows 88.88).
Has Circulation Fan stopped?
Is there fuel in tank? Is tank valve open?
Has Fuel Constant Level Valve Set Lever
raised and lowered?
Is ON/OFF switch ON?
Is operation mode on Manual?
Is set temperature in High position?
Is Fusible Link Valve "open"?
NOTE: Air Damper in the following Flow Charts refers to the round disk that is installed over the flue pipe air intake flange.
There are different ones for the standard installation and installations with flue pipe extensions.
pg. 46A

2. 1. Is Igniter red? Check visually through the Combustion Chamber
viewing window or feel igniter
cover after 3.5 minutes
prepurge preheat. It
should be warm to
the touch.
Replace or check
Circuit Board
Failure of Circuit Board
Incorrect wiring of Flame Sensor or
Ground
Correct wiring.
Is there flame? 1.
Yes
Correct or change
Is RUN
lamp lit?
Flame Sensor Rod touching burner
parts.
Yes
No Ignition No
Replace Air
Pressure Switch
Yes
Does
Combustion
Blower motor
operate?
Failure of Air Pressure Sensor
Replace Solenoid Pump No
Failure of Solenoid Pump
Yes
Reset the fuel
Constant Level Valve
Has Constant Level Valve safety
tripped? No No
Replace Combustion
Blower Motor
NOTE:
PCB stands for
Printed Circuit
Board
Failure of Combustion Blower Motor
1. Push ON/OFF Switch OFF
2. Remove Igniter
3. Disconnect wiring for
Solenoid Pump.
4. Push ON/OFF Switch ON
Is wiring
correct?
Yes
Failure of Circuit Board
Replace or check
Circuit Board No
Incorrect wiring
Correct wiring
Soot adhering to combustion
chamber interior
Clean gently with
brush, etc.
Is Igniter red?
Yes
Failure of Solenoid Pump
Replace Solenoid Pump
Is Display
Window lit?
Replace Igniter
Yes No
Failure of Igniter
Is there 110V
at "B" pins on
Circuit Board?
Replace or check
Circuit Board
Failure of Circuit Board
Yes No
Correct wiring
Incorrect wiring
Failure of Igniter relay
on PCB. Replace board
Check Fuse
(F1)
Is there 110V at "B" plug?
Normal No
Replace or check
Circuit Board
Failure of Circuit Board
Put in Manual mode
Open
Is on Auto operation mode?
Change
Fuse; plug in power
cord
Replace or check
Circuit Board
Failure of Circuit Board
Normal
Previous Fuse open
Leave in new Fuse
Short circuit of lead wire
Correct or change
Open
pg. 46B
Failure of Circuit Board
Replace or check
Circuit Board

3. 2. 3. 4. 5. Is Solenoid Pump operating? Is there water in the fuel?
Water gathering in fuel tank
Discharge water
Is air trapped
in fuel line?
Yes
Yes
Yes
No fuel feed;
No Ignition
Fuel not fed because of surface
tension of water
Clean burner joint
Burner joint clogged (Fuel Line pas-
sageway into Combustion Chamber
near base of Burner Pot)
Replace handle of
fusible link valve or
open valve No No No
Check wiring to
plug "K"
Fusible link valve closed on M-422
Reset fuel Constant
Level Valve
Normal
Tripped safety on fuel Constant
Level Valve
Replace Solenoid Pump
Correct or replace wires
Failure of Solenoid Pump
Abnormal
Wiring failure
Straighten fuel line to
remove air pocket, or
correct fuel line
installation
Air lock 3.
Is Fuel Constant
Level Valve Lever
set?
Yes
Push Fuel Constant
Level Valve Lever
4 or 5 times
Extinguished
soon after
Ignition
Fuel not entering into valve
1. Push ON/OFF
Button to "OFF"
2. Refuel heater
3. Turn heater on No
Fuel shortage
Overheat condition
1. Unplug heater
2. Remove air-flow
obstructions and/or
determine cause of
overheating
3. Replace cover &
restart heater
Make GENERAL CHECKS from
previous page.
Is fuel head too low? See Section 2: INSTALLATION
If using a Lifter, check Lifter installation specifications.
Is unit placed horizontally?
Is fuel line length correct? 4.
Normal
Air present in fuel line
Flame does
not increase
when set
at "High"
Is Display
Window lit?
Yes
Correct fuel line
Failure of Solenoid Pump
Replace Solenoid Pump
Wiring failure
Correct wiring No
Failure of Solenoid Pump
Replace Solenoid Pump
Failure of Circuit Board
Replace or check
Circuit Board 5.
Abnormal
Not as specified
Correct as specified
Allow heater to cool
completely.
Tighten all
connections.
Poor flame; sounds of combustion;
soot at the reat of the heater.
Is not a failure, but is apt to occur.
Loose flue pipe
pg. 47

4. 6. 7. Is unit placed horizontally? Is flue pipe too long
or have too many bends?
See Section 2:
INSTALLATION
Does
Combustion Fan
work properly?
Check for obstructions
such as wasps nests
in exhaust or
air supply
piping 6.
Does
Damper Solenoid
work
properly?
Normal
Normal No
Smoke produced
when set "High"
Failure of Damper Solenoid Assy
Replace Damper
Solenoid Assy
Yes
Check outside
of flue pipe for
flow of air and
exhaust
Abnormal
Abnormal
Abnormal
Clean out intake and
exhaust ducts
Intake or exhaust line clogged
Normal
Is Air Damper
installed according
to specifica-
tions?
Yes
Fuel Solenoid Pump malfunctioning
Replace Solenoid Pump No
Install Air Damper ac-
cording to specifications
Combustion Fan failed
Replace Combustion
Blower Assembly
Clogged air supply or exhaust piping
Remove obstructions
Not as specified
Correct as specified 7.
Is igniting
time too long?
(Usually 0.5 to
1 min)
Is Air Damper
installed according
to specifica-
tions?
Combustion
noise is made
soon after
igniting
Normal
Normal
See Symptom #5
Abnormal
Abnormal
Mount Air Damper
as needed
Too much air flow
Igniter mounted incorrectly
Mount properly
pg. 48A

5. 8. Is fuel pure kerosene? Is heater mounted horizontally?
Is external fuel tank too low?
(See Section 2: INSTALLATION)
Install Air Damper as needed
(see Symptom #5).
Is there an obstruction in the
Combustion Air System? 8.
Does
flame extend to
whole area of
burner? Is
Igniter properly
installed?
Combustion
Chamber window
gets smoky
after running
Normal
Yes
Yes
Install Combustion
Ring properly
Combustion Ring is installed
improperly No
Combustion Ring is broken
Replace Combustion
Ring Assembly No
Replace gasket;
correctly install cover
Air leaks from Igniter cover
Switch Set
temperature to
High & Low
5-6 times
Flame extends
Supplies only a small amount of fuel
due to dust or bubbles in fuel
delivery parts
Instruct customer about
filter & reset lever
Abnormal
Flame does not extend
Failure of Solenoid Pump
Replace Solenoid Pump
Not as specified
Correct as specified
pg. 48B

6. 9. Is window curtain too close to the rear of the unit?
Is Circulation Fan
Guard dusty? 9.
Yes
The Overheat
Thermostat is
activated
Window curtain or other obstruction
covers circulation air inlet.
Clean guard
Keep curtain from unit No
Does
Circulation Fan
operate
properly?
Yes
Obstacle covers circulating air outlet
Remove obstacle No
Failure of Printed Circuit Board
Replace or check PCB
Circulation Fan failed
Repair Fan Motor
Incorrect wiring
Repair or replace wiring
pg. 49

7. 10. Does 88.88 blink in the display window? Is there fuel? (M-422)
Is Empty LED
lit? (M-422)
Failure of resistor R38 - R39
Yes
Yes
Yes
If problem is found to
be in the PCB, do not
attempt to repair.
Replace & send PCB
through your distributor
to MPI for repair.
No operation
Failure of capacitor C20 No
Plug in
AC cord No
Is temperature
displayed in
display window? No
Failure of resonator XL1
Yes
Press ON/OFF
button to ON
Failure of resistor R59
Failure of microprocessor IC1 No
NOTE:
PCB stands for
Printed Circuit
Board
Remove the connector CN1 of operation
circuit board from PCB and then
jumper pins T1 & T6 on PCB
Replace operation
circuit board CN1
Failure of operation circuit board CN1
Does
heater start to
operate?
Yes
Failure of resonator XL1
Failure of resistor R59
NOTE:
DC voltages are
measured with
respect to EP on
PCB No
Failure of microprocessor IC1
No fuel
Refill fuel
At AC cord
plug-in, does voltage
at TP7 turn High
from Low?
Failure of Microprocessor IC-1
Is there
12VDC
at TP3?
Is there
5VDC
at TP2?
Yes
Yes
Yes
Failure of comparator IC13
Failure of resistor R29 - R32 No No
Failure of capacitor C18 No
Failure of switch SW1 (Reset)
Failure of IC2
Failure of capacitor C9
Fuse F1 open
Replace fuse
Failure of transformer
Replace transformer
Failure of diode D6 - D9
pg. 50
Failure of capacitor C8

8. 11. Does Combustion Blower work during prepurge & igniting? Is
Igniter red on
preheat?
Does
Air Pressure
Switch work
normally?
A on
next page
Yes
Yes
Yes
No ignition No No No
Replace air
pressure switch
Failure of air pressure switch
Rubber hose is blocked
or disconnected
Clear or connect
rubber hose
Incorrect wiring
Correct wiring
Failure photo-triac IC8
Failure of triac Q1
Is there
12VDC between
TP3 & IC6
pin 13?
Failure of resistor R1, R51
Yes
Failure of capacitor C2
Replace
combustion blower
Failure of combustion blower
Incorrect wiring of combustion blower No
Correct wiring
Failure of microprocessor IC1
Failure of inverter array IC6
Is there
12VDC on coil
of relay RL1 on
preheat?
Failure of relay RL1
Yes
Fuse F2 open
Replace fuse
Igniter open
Replace igniter No
Failure of microprocessor IC1
pg. 51
Failure of inverter array IC6

9. 11. A from previous page Does Solenoid Pump work? Yes
Check fuel supply
parts
Failure of fuel supply parts No
Failure of resistor R2 - R9
Failure of capacitor C4 - C6
Failure of zener diode ZD1
Is there
160VDC across
diode bridge
D2?
Failure of diode D3 - D5
Yes
Failure of trigger diode TD
Failure of thyristor Q2, Q3 No
Failure of diode bridge D2
Failure of microprocessor IC1
Failure of inverter array IC6
Failure of diode D17
Failure of resistor R53
Failure of photo-triac IC11
Failure of transistor Q6, Q11
pg. 52

10. 13. Is there 1.2VDC on IC3 pin 6? Is there more than 1.3VDC at TP6?
Yes
Yes
Yes
Flame failure
Failure of comparator IC3 No No No
Failure of microprocessor IC1
Is there
0.2VDC or less
on Q7
collector?
Failure of resistor R33, R34
Yes
Incorrect installation of
flame sensor rod
Correct installation
Failure of wiring for flame
sensor and ground
Correct wiring No
Failure of resistor R27
Failure of diode D19
Failure of capacitor C29
Failure of transistor Q7
Failure of transformer
Replace transformer
Failure of capacitor C14 - C16
Failure of resistor R10, R22 - R24
Failure of resistor R , R25
pg. 53A

11. O N 13. FLAME ROD BYPASS CIRCUIT
For testing purposes: a flame detector rod bypass circuit can be made up,
consisting of 2 insulated alligator clips, 2 - 6" pieces of insulated copper wire,
1 - 1/4 watt 400 Volt diode, and 1 - 1/4 watt 100K resistor. These components
are to be soldered together in sequence as shown in the diagram below
(note component sequence & polarity.)
Once the bypass circuit is made, turn the unit on. Immediately after the prepurge
preheat cycle, when the mode light comes on, disconnect the wires from the
O and N pins on the PCB and replace with the bypass circuit. The unit should then
continue functioning as though it had a good flame inside the burn chamber,
and service tests such as fuel flow can be checked.
Note: WARNING, after all tests are completed, replace original flame rod wires,
as it is a vital safety issue. O N
1N4004
100K
Clips
pg. 53B

12. 14. Failure of microprocessor IC1 Connect 10K resistor to Q
pins on PCB
and then set
temperature
from Low
to High Is
temperature
display
normal?
Is solenoid
pump able to
change fuel flow
rate?
Is circulation
fan motor able to
change speed?
Yes
Failure of inverter array IC6
Change of burn
mode: High--Low,
is improper
Yes
Yes
Failure of photo-triac IC8, IC9
Failure of triac Q1 No No No
Failure of resistor R1, R51, R52
Failure of capacitor C2
Failure of Combustion Blower
Replace
combustion blower
Failure of resistor for
Combustion Blower
Replace resistor for
Combustion Blower
Failure of Damper Solenoid
Replace
damper solenoid
Failure of photo-triac IC7
Failure of microprocessor IC1
Failure of inverter array IC6
Failure of circulation fan motor
Replace circulation
fan motor
Failure of microprocessor IC1
Failure of photo-coupler IC12
Failure of inverter array IC6 Is
there approx.
2.8VDC at
TP4?
Failure of solenoid pump
Replace solenoid pump
Yes
Failure of microprocessor IC1
Failure of resistor R12, R13 No
Failure of capacitor C11
pg. 54