OWNER’S MANUAL
Manufactured Home
Downow Gas Furnace:
MGD-B Series
Heat Controller, Inc. • 1900 Wellworth Ave. • Jackson, MI 49203 • (517)787-2100 • www.heatcontroller.com
Owner’s Manual MGD-B SERIES GAS FURNACE Heat Controller, Inc.
1
Heat Controller, Inc. MGD-B SERIES GAS FURNACE Owner’s Manual
See warranty card that was provided with your unit.
2
Owner’s Manual MGD-B SERIES GAS FURNACE Heat Controller, Inc.
G18D Series Gas Furnace OWNER’S MANUAL
Mortex Products Inc. / Fort Worth, TX 76106
G18D Owner’s Manual
3
12. After three (3) trials for ignition, if the furnace will
not operate, follow the instructions, “TO TURN OFF
GAS TO APPLIANCE” and call your service
technician or gas supplier.
13. Replace control access panels.
AUTO IGNITION GAS VALVE
TO TURN OFF GAS TO FURNACE
Automatic Ignition Models
1. Set thermostat to the lowest setting.
2. Turn o all electric power to the appliance if service
is to be performed.
3. Remove control access panels.
4. Push the switch on the gas valve to the “OFF”
position. DO NOT FORCE.
5.
Replace control access panels.
SEQUENCE OF OPERATION
Connuous Blower
On cooling / heang thermostats with a AUTO / ON fan
switch, when the fan switch is set to the ON posion, 24 VAC
is sent from the red thermostat wire to the green thermostat
wire energizing the blower motor cooling fan terminal (“G”
Terminal) on the control board. The control board swi
tches
115 VAC to the COOL terminal on the control board and the
motor runs on the selected blow
er motor speed tap.
Intermient Blower - Cooling
On cooling / heang thermostats with a AUTO / ON fan
switch, when the fan switch is set to the AUTO posion and
the thermostat calls for cooling, 24 VAC is sent from the red
thermostat wire to the green thermostat wire and the ye
llow
thermostat wire. The green thermostat wire will energize the
blower motor cooling fan terminal (“G” Terminal) on th
e
control board. The control board switches 115 VAC to the
COOL terminal on the control board and the motor runs on
the selected blower motor speed tap. The yellow thermostat
wire (“Y”) will send 24 VAC to the contactor on the outdoor
unit causing the contactor to close, energizing the
compressor and the outdoor fan motor.
Intermient Blower - Heang
On cooling / heang thermostats with an AUTO /
ON fan
switch, when the fan switch is set to the AUTO posion and
the thermostat calls for heang, 24 VAC is switched from the
red thermostat wire to the white thermostat wire. The
control board has a programmed me delay period that will
place 115 VAC on the HEAT terminal on the control board at
the compleon of the me delay and allow the blower motor
run on the selected blowe
r motor speed tap.
Power ON
When the line power (115 VAC) is turned on to the furnace
the 115 VAC is applied between the L1 terminal and the
neutral terminal on the control board. The step down
transformer applies 24 VAC to the “24 VAC” and the “COM”
terminals on the control board. The control board places 24
VAC from the grey wire on the 9 pin plug, thru the upper limit
control (Manual Reset), thru the blue wire to
the main limit
(Auto Reset) and returns 24 VAC signal thru the orange wire
back to the 9 pin plug on the control board. This signal
indicates to the control board sowa
re that the limit circuit is
closed. The control board soware then checks for a 24 VAC
signal from the pressure switch. If the pressure switch is open
the soware checks the flame sensor to determine if a flame
is present. If no flam
e is present then the sowa
re places the
control board into the ready mode which is indicated by a
steady green diagnosc indicator light.
NOTE:
If a limit is open when the line power (115 VAC) is turned on;
the control board soware switches 115 VAC to the HEAT
terminal on the control board sending 115 VAC to the indoor
fan motor energizing the indoor fan on the selected speed
tap and the diagno
sc led wi
ll flash four flashes.
NOTE:
If the pressure switch electrical contacts are stuck closed
nothing will happen unl there is a call for heat. Upon a call
for heat the control board soware will wait 30 seconds for
the pressure switch electrical contacts to open. During this
me, none of the components will operate. Aer 30 seconds
the diagnosc indicator led wi
ll flash two flashes and none of
the components will operate.
Heang Cycl
e
When the thermostat switch is set to the HEAT posion, the
thermostat fan switch is set to the AUTO posion and the
thermostat calls for heat; 24 VAC is switched from the red
thermostat wire to the white thermostat wire sending a 24
VAC signal to the “W” terminal on the control board. This
signal tells the control board soware there is a call for heat.
The control board swi
tches 115 VAC to the black wires on the
6 pin plug located at the boom right side of the control
board, energizing the combuson air booster motor.
3
Heat Controller, Inc. MGD-B SERIES GAS FURNACE Owner’s Manual
G18D Series Gas Furnace OWNER’S MANUAL
Mortex Products Inc. / Fort Worth, TX 76106
G18D Owner’s Manual
4
The igniter warm-up period is extended to 27 seconds then,
24 VAC is sent to the gas valve solenoid opening the solenoid
and starng the flow of gas. If a flame is established for more
than 10 seconds during the retry the unit will connue to
operate normally and the control board will clear the ignion
retry counter. If a flame has not been established then the
control board will advance the retry counter and will connue
the ignion retry operaon. The ignion retry operao
n will
aempt to re-ignite the gas burner a total of three ignion
cycles during a call for heat from the thermostat. If the
burner flame has not been established aer the third ignion
retry cycle the control board will go into a so lockout for a
period of one hour. If there is s
ll a call for heat aer the one
hour lockout the furnace will iniate a normal start cycle. If
the problem has not been corrected the furnace wi
ll lockout
again aer the three ignion retries.
Call For Heat Removed
If the call for heat from the thermostat is removed from the
control board before the board can resume normal operaon
the control board will clear the ignion retry counter, will
clear a so lockout and will clear any fault codes.
Call For Heat Removed With Gas Valve Stuck Open
If the furnace is running normally and the call for heat from
the thermostat has been remove
d the 24 VAC signal to the
gas valve solenoid will be removed. If the control board
soware indicates a microamp signal is present at the flame
sensor indicang a flame is present the control board will
keep 115 VAC present to the combuson air booster motor,
115 VAC to the heat terminal for the indoor fan to kee
p the
indoor fan motor energized and will flash a error code of 5
flashes indicang a flow
of gas with no call for heat. The
furnace will connue to operate at this condion unl the
gas flow has been interrupted and the flame has been
exnguished.
OBSERVING BURNER OPERATION
The combuson air booster motor is located inside the white
plasc assembly aached to the 4” round galvanized pipe.
When the combuson air booster motor has been energized
the fans create a flow of air through the booster motor
assembly and the burner box that produces a negave
pressure at the top of the booster motor assembly and a
posive pressure at the burner box. A tube is aached to the
pressure port at the top of the booster motor assembly and
the top of the burn
er box that extends to the pressure ports
on the pressure switch, providing the negave and posive
pressures to the switch. If the pressures applied to the
posive and negave ports (Differenal Pressure) of the
pressure switch exceed -0.2” wc +/ .05” wc the switch
electrical contacts close providing a 24 VAC signal
back to the
control board thru the blue wires aached to the 9 pin plug
in
dicang to the control board soware the pressure switch
has closed.
When the pressure switch has closed the control board starts
a 30 second ignion warm up. This gives the hot surface
igniter 30 seconds to obtain its normal operang
temperature. Aer the 30 second ignion warm up, the
control board sends 24 VAC to the thru the brown wires on
the 9 pin plug to the gas valve solenoid for 10 seconds which
w
ill open the gas valve and start the flow of gas. The hot
surface igniter should ignite the flow of gas and start the
flame stabilizaon period. During the flame stabilizaon
period the flame sensor will send a microamp signal of 1.5
to 3.7 microamps (0.0000015 to 0.0000036 amps) thru the
yellow wire that is connected to the
9 pin plug on the control
board signaling to the control board soware that a fla
me is
present. The indoor blower me delay will start a 50 second
on delay aer the flame stabilizaon period has concluded
and the control board will place 115 VAC on the HEAT
terminal of the control board energizing the indoor fan in the
heang mode. The furnace will connue to operate unl the
call for heat from the thermostat has been sasfied. At this
point the gas valve solenoid will be de-energized, the burner
fla
me will be exnguished and the control board soware will
start a 50 second indoor fan off delay. When the indoor fan
has de-energized the control board will indicate a steady
green light on the diagnosc indicator indicang the control
board is ready to resume normal operaon.
Ignion Retry
If the
burner flame has not been established or has been
interrupted when the thermostat is calling for heat; the
c
ontrol board will start the ignion retry operaon. During
the retry operaon the combuson air booster motor will
connue to operate. The control will start a 15 second purge
to vent any unburned gas from the heat exchanger.
1. Observe burner to make sure it ignites and to
observe the flame co
lor. With Natural gas, the
flame will be blue with yellow ps; with Propane
ga
s, a yellow flame can be expected.
2. Allow furnace to heat up unl the blower cycles on.
(2-1/2 min.)
3. Turn wall thermostat down.
4. Observe main burner flame to make sure it shuts
off.
5. Let furnace cool and blower turns off.
6. If any abnormalies should occur, such as the burner
failing to light or to turn off, the flame looks sooty o
r
it seems to be “floang” around inside the heat
exchanger, call a qualifie
d service technician for
service.
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Owner’s Manual MGD-B SERIES GAS FURNACE Heat Controller, Inc.
G18D Series Gas Furnace OWNER’S MANUAL
Mortex Products Inc. / Fort Worth, TX 76106
G18D Owner’s Manual
5
IF FURNACE FAILS TO OPERATE PROPERLY
1. Check setting of the wall thermostat and position of
the heat/cool switch if air conditioning is installed.
2. Check to see that electrical power is “ON”.
3. Check to see that system switch is “ON”.
4. Check to see that lever on gas valve is in the “ON”
position.
5. Make sure that air lters are clean, supply registers
are open and return air grilles are not obstructed.
6. Be sure that furnace ue and inlet air pipes are open
and unobstructed.
7. Observe the Diagnostic Light. This light is visible
through a slot on the control panel cover and ashes
when there is a service problem. The diagnostic
codes are:
Steady On: Normal Operation
One Flash: Ignition Failure
Two Flashes: Pressure switch stuck closed.
Three Flashes: Pressure switch failed to close.
Five Flashes:
Gas valve energized or ame sensed at ame
sensor with no call for heat.
Six or Rapid Flash: Reversed polarity.
If the cause for failure to operate properly is not an
electrical switch, thermostat switch or gas valve switch
in the o position; call a qualied service technician or
your gas supplier. DO NOT ATTEMPT TO REPAIR THE
APPLIANCE YOURSELF.
Four Flashes: Limit switch is open.
THE FURNACE CONTROLS AND THEIR FUNCTION
• Auto Ignition Units with “ON-OFF” System Switch -
The switch is on the right side of the furnace control
box and turns electrical power to the furnace on or
o. It must be “ON” for the furnace to operate.
• Limit Switch - All furnace models are protected by
two (2) temperature limit safety switches. The lower
limit switch (inside furnace control box) is an
automatic reset type. Press the red button on the top
of the limit to reset. If burner starts but the blower
does not start do not press the red button again. Call
a qualied service technician for service. The limit
switch by the furnace
blower is a manual reset type.
• Fan Switch - Furnaces have a temperature sensing
device that turns on the blower when sufcient heat
has built up inside the furnace.
• Gas Valve - The gas valve for all models are 100%
shut-o type and will fail safe if for some reason the
gas is turned o .
INSPECTION AND MAINTENANCE
BY THE HOMEOWNER
• Make a visual inspection of the furnace every 30
days. Do the following:
• Filters- Clean lters at least every (3) months and
replace as needed. Size; 16”x20”x1”
• Motor Lubrication- None: The combustion and air
circulator motors are permanently lubricated.
• Return Air - On some closet installations, the return
air opening may be in the oor. DO NOT cover or
obstruct these oor openings or any other return air
opening to the closet.
• Heat Exchanger - under normal conditions, no
cleaning is needed. If cleaning becomes necessary,
only a service technician should do so. Chemicals
should not be used to clean the heat exchanger.
• Furnace Vestibule - periodically remove furnace
panels and clean the vestibule area to remove dust
and lint
. Shut o all electrical power to the unit
before cleaning.
• When you’re away - The furnace has safety controls
to shut the unit down if there is a malfunction.
Therefore do not assume it can operate unattended
for prolonged time periods. There is a damage
possibility to your home in freezing weather, have a
neighbor or family member check your home daily.
INSPECTION AND MAINTENANCE BY A SERVICE
TECHNICIAN
Annual furnace maintenance and Inspection is
recommended.
• Replace air and clean dust and lint from
furnace and area.
• Remove blower assembly and clean blower wheel
and motor.
• Inspect the combustion chamber, collar and roof
jack.
• Check the gas valve and gas line connections for
leaks.
• Make adjustments as needed for good operation.
SEASONAL SERVICE INFORMATION
In regions where there is heavy snow accumulation, a
roof jack crown extension is recommended to prevent
blockage of the roof jack combustion air openings.
During extreme cold weather, ice may form on the
furnace roof jack. Small amounts of ice on the roof jack
will present no problem to proper furnace operation.
Excessive ice formation could restrict the combustion air
supply to the burner causing inefcient burner operation.
If excessive ice has formed on the inlet or exhaust
portions of the roof jack, it must be carefully removed.
5
Heat Controller, Inc. MGD-B SERIES GAS FURNACE Owner’s Manual
PRE-TROUBLESHOOTING CHECK LIS
T
YOU MUST HAVE THE FOLLOWING TOOLS TO PREFORM THE TROUBLESHOOTING DESCRIBED BELOW
:
1 - VOLT, AMP, OHM METER
VOLTAGE RANGE 0 - 300 VOLTS
VISE GRIP PLIERS
CURRENT RANGE 0.0 AMPS TO 1 MICROAMPS (0.000001 AMPS). IF YOU CURRENT METER DOES NOT HAVE A MICROAMP (µa) READING; mA.
YOU CAN USE THE MILLIAMP (mA) PROVIDING THE SCALE READS 0.000
G18D SERIES CONTROL BOARD
TROUBLE SHOOTING GUIDE
8
G18D Series Gas Furnace OWNER’S MANUAL
Mortex Products Inc. / Fort Worth, TX 76106
G18D Owner’s Manual
CONDITION FURNACE OPERATION DIAGONSIC LED STEP PROBABLE CAUSE OF PROBLEM TROUBLESHOOTING SOLUTION
CALL FOR HEAT
FURNACE RUNS NORMALLY
STEADY ON N/A N/A N/A
BURNER FLAME
CALL FOR HEAT
WILL NOT STAY LIT
ONE FLASH
1
SENSOR WIRE DEFECTIVE OR SENSOR IS BROKEN.
USE MICROAMP METER TO DETERMINE IF FLAME SENSOR CURRENT
READING IS BETWEEN 1.0 MICROAMP (0.000001 AMP) AND 3.7
MICROAMPS (0.0000037 AMPS) ON THE YELLOW WIRE. THE METER
MUST BE CONNECTED IN SE
RIES BETWEEN THE FLAME SENSOR AND THE
CONTROL BOARD. A CURRENT FLOW OF APPROXIMATELY 3.7
MICROAMPS WILL BE PRESENT ON THE YELLOW SENSOR WIRE WHEN
THE BURNER FLAME IS PRESENT AT THE FLAME SENSOR.
IF THE YELLOW FLAME SENSOR WIRE QUICK CONNECT TERMINAL IS CONNECTED AND
THE BURNER FLAME SENSOR CURRENT READING IS BETWEEN 1.0 - 3.7 MICROAMPS
(0.000001 - 0.0000037 AMPS) GOTO STEP 4; IF THE BURNER FLAME SENSOR CURRENT
I
S NOT READING IS BETWEEN 1.0 AND 3.7 MICROAMPS; THEN DISCONNECT THE QUICK
CONNECT TERMINAL AND CHECK THE FLAME SENSOR CURRENT TO GROUND. IF THE
READING IS NOT BETWEEN 1.0 - 3.7 MIC
ROAMPS (0.000001 - 0.0000037 AMPS) THEN
REPLACE THE FLAME SENSOR. IF THE READING IS BETWEEN 1.0 AND 3.7 MICROAMPS
THEN GOTO STEP 2.
2
SENSOR WIRE DISCONNECTED OR SENSOR WIRE
IS BROKEN.
USE
MICROAMP METER TO DETERMINE IF FLAME SENSOR CURRENT
READING IS BETWEEN 0 MICROAMP (0.000000 AMP) AND 3.7
MICROAMPS (0.0000037 AMPS) ON THE YELLOW WIRE. IF YOUR
CURRENT METER DOES NOT HAVE A MICROAMP READING YOU CAN USE
THE MILLIAMP PROVIDING THE SCALE READS 0.000000 AMPS. THE
METER MUST BE CONNECTED IN SERIES BETWEEN THE FLAME SENSOR
AND THE CONTROL BOARD. A CURRENT FLOW OF APPROXIMATELY 3.7
MICROAMPS
WILL BE PRESENT ON THE YELLOW SENSOR WIRE WHEN
THE BURNER FLAME IS PRESENT AT THE FLAME SENSOR.
IF THE YELLOW FLAME SENSOR WIRE QUICK CONNECT TERMINAL IS CONNECTED AND
THE BURNER FLAME SENSOR CURRENT IS NOT READING IS BETWEEN 1.0 AND 3.7
MICROAMPS (0.000001 - 0.0000037 AMPS) WITH THE CURRENT METER CONNECTED IN
SERIES BETWEEN THE FLAME SENSOR AND THE CONTROL BOARD; THEN UNPLUG THE 9
PIN PLUG AT THE CONTROL BOARD AND PERFORM A RESISTANCE TEST (OHM (Ω)
TEST)
ON THE YELLOW FLAME SENSOR WIRE. IF THE OHMS (Ω) METER DOES NOT INDICATE A
READING OR SHOWS THE ∞ SYMBOL (SHOWS A OPEN WIRE); THEN REPLACE THE FLAME
SENSOR WIRE OR THE WIRE HARNESS. IF THE OHMS READING OF THE SENSOR WIRE IS
CLOSE TO ZERO OHMS THEN GOTO STEP 3.
3
TOO MUCH DRAFT CAUSING BURNER FLAME TO
LIFT AWAY FROM THE FLAME SENSOR
USE AMP METER TO DETERMINE IF FLAME SENSOR CURRENT READING
IS BETWEEN 1.0 MICROAMP (0.000001 AMP) AND 3.7 MICROAMPS
(0.0000037 AMPS) ON THE YELLOW WIRE BETWEEN THE SENSOR AND
THE CONTROL BOARD WHEN THE BURNER FLAME IS PRESENT AT THE
FLAME SENSOR.
IF THE BURNER FLAME SENSOR CURRENT READING IS NOT BETWEEN 1.0 - 3.7
MICROAMPS (0.000001 - 0.0000037 AMPS)
AND THE BURNER WILL NOT STAY LIT THEN
CAFEFULLY BEND SENSOR UP UNTIL THE SENSOR IS IN THE BURNER FLAME OR UNTIL
FLAME SENSOR MICROAMPS ARE BETWEEN 1.0 - 3.7 MICROAMPS (0.000001 -
0.0000037 AMPS). USE VISE GRIP PLIERS TO HOLD SENSOR ROD WHEN BENDING
FLAME SENSOR SO THE CEREMIC DOES NOT BREAK OR CRACK. IF NO MICROAMP
READING IS PRESENT EVEN AFTER BENDING THE SENSOR UP TO A 90 DEGREE ANGLE IN
FR
ONT OF THE BURNER THEN REPLACE THE SENSOR. IF A READING ABOVE 1.0
MICROAMPS IS PRESENT BUT BURNER WON'T STAY LIT GO TO STEP 4.
4
THERE IS A BROKEN WIRE TO THE GAS VALVE OR
ONE OF THE GAS VALVE WIRES HAS A BAD
CONNECTION.
USE OHM (Ω)
METER TO DETERMINE WHICH WIRE TO THE GAS VALVE IS
DEFECTIVE AND REPLACE THE WIRES.
REMOVE THE 9 PIN PLUG FROM THE CONTROL BOARD AND THE WIRES FROM THE GAS
VALVE. USE A OHM (Ω) METER TO DO A RESISTANCE TEST ON BOTH OF THE BROWN
WIRES FROM THE PIN ON THE 9 PIN PLUG TO THE GAS VALVE. WHEN PREFORMING THIS
TEST MOVE THE WIRE HARNESS TO CHECK FOR A BAD CONNECTION. IF A CONNECTION
IS BAD THE METER READING WILL CHANGE FROM ZERO OHMS TO SHOWING OPEN OR
THE INFINITY (∞) SYMBOL. IF A WIRE
IS FOUND TO BE DEFECTIVE OR HAS A BAD
CONNECTION; THEN REPLACE THE WIRE OR WIRE HARNESS. IF THE BOTH WIRES ARE
SH
OWING CLOSE TO ZERO OHMS (Ω) THEN GOTO STEP 5.
5
CONTROL BOARD IS DEFECTIVE
USE A MICROAMP METER TO MEASURE THE FLAME SENSOR CURRENT
READING. THE READING MUST BE BETWEEN 1.0 MICROAMP (0.000001
AMP) AND 3.7 MICROAMPS (0.0000037 AMPS) WITH THE BURNER
FLAME PRESENT AT THE SENSOR.
IF THE BURNER FLAME SENSOR CURRENT READING IS BETWEEN 1.0 - 3.7 MICROAMPS
(0.000001 - 0.0000037 AMPS) AND THE BURNER WI
LL NOT STAY LIT THEN REPLACE THE
CONTROL BOARD ONLY IF THE CHECKS IN STEPS 1, 2, 3, AND 4 HAVE BEEN PREFORMED.
MGD-B SERIES CONTROL BOARD
6
Owner’s Manual MGD-B SERIES GAS FURNACE Heat Controller, Inc.
G18D SERIES CONTROL BOARD
TROUBLE SHOOTING GUIDE
9
G18D Series Gas Furnace OWNER’S MANUAL
Mortex Products Inc. / Fort Worth, TX 76106
G18D Owner’s Manual
CALL FOR HEAT
BURNER FLAME WILL NOT LIGHT
ONE FLASH
1
IN-LINE HAND VALVE, BALL VALVE OR GAS COCK
IS TURNED OFF.
CHECK THE INCOMING GAS LINE FOR A CLOSED HAND VALVE, GAS COCK,
OR BALL VALVE.
IF A HAND VALVE, GAS COCK, OR BALL VALVE IN THE GAS LINE IS IN THE OFF POSITION;
TURN THE VALVE TO THE ON POSITION. IF ALL OF THE VALVES IN THE GAS LINE ARE IN
THE ON POSITION THEN GOTO STEP 2.
2
ON / OFF SWITCH ON TOP OF GAS VALVE IS
TURNED TO THE OFF POSITION.
CHECK THE ON / OFF SWITCH ON TOP OF THE GAS VALVE.
IF THE GAS VALVE SWITCH IS TURNED TO THE OFF POSITION; TURN THE SWITCH TO THE
ON POSITION. IF THE GAS VALVE SWITCH IS IN THE ON POSITION THEN GOTO STEP 3.
3
BAD OR BROKEN IGNITER
UNPLUG THE QUICK CONNECT TERMINALS ON THE WHITE WIRES TO
THE IGNITOR AND USE A VOLT METER TO CHECK FOR 115 VAC DURING
THE IGNITION CYCLE. IF 115 VAC IS PRESENT THEN RECONNECT THE
WIRES.
IF 115 VAC IS FOUND ON THE WHITE WIRES GOING TO THE IGNITER DURING THE
IGNITION CYCLE BUT THE IGNITER DOES NOT GLOW; REPLACE THE IGNITER. IF THE
IGNITER IS GLOWING THEN GOTO STEP 4.
4
NO GAS LINE PRESSURE AT THE GAS VALVE
USE INCHES OF WATER (INWC) PRESSURE GAUGE OR USE A "U" TUBE
MONOMETER TO CHECK THE GAS LINE PRESSURE ON THE INCOMING
SIDE OF THE GAS VALVE. THE LINE PRESSURE SHOULD BE 7.0 INCHES OF
WAT
ER (INWC) FOR NATURAL GAS OR 11.0 INCHES OF WATER (INWC)
FOR PROPANE GAS.
IF THERE IS 7.0 INCHES OF WATER (INWC) FOR NATURAL GAS OR 11.0 INCHES OF WATER
(INWC) FOR PROPANE GAS AT THE INLET SIDE GAS VALVE THEN PROCEED TO STEP 5. IF
THERE IS NO PRESSURE AT THE INLET SIDE OF THE GAS VALVE PROCEED TO STEP 1.
5
GAS VALVE SOLINOID NOT OPENING
USE VOLT METER TO CHECK FOR 24 VAC ON GAS VALVE ELECTRICAL
TERMINALS DURING IGNITION CYCLE; (30 SECONDS AFTER THE IGNITER
HAS BEEN ENERGIZED) IF THE GAS VALVE TOGGLE SWITCH IS NOT
TURNED OFF AND 24 VAC IS NOT PRESENT AT THE GAS VALVE
E
LECTRICAL TERMINALS; THEN USE A INCHES OF WATER (INWC)
PRESSURE GAUGE OR USE A "U" TUBE MONOMETER TO CHECK THE GAS
VALVE OUTLET (MANIFOLD) PRESSURE. THE OUTLET (MANIFOLD)
PRESSURE MUST BE 3.5 INCHES OF WATER (INWC) FOR NATURAL GAS
AND 10.0 INCHES OF WATER (INWC) FOR PROPANE GAS. IF THERE IS NO
OUTLET PRESSURE THEN REPLACE THE GAS VALVE. IF 24 VAC IS NOT
PRESENT ON THE GAS VALVE ELECTRICAL TERNINALS THEN GO TO STEP
6
.
IF THERE IS 24 VAC TO THE GAS VALVE ELECTRICAL TERMINALS, THE GAS VALVE TOGGLE
SWITCH IS IN THE "ON" POSITION, AND THERE IS NO FLAME PRESENT; THEN CHECK THE
GAS VALVE OUTLET (MANIFOLD) PRESSURE TO DETERMINE IF THERE IS 3.5 INCHES OF
WATER (INWC) GAS PRESSURE FOR NATURAL GAS OR 10.0 INCHES OF WATER (INWC)
GAS PRESSURE FOR PROPANE GAS WHEN THERE IS 24 VAC PRESENT AT THE ELECTRICAL
T
ERMINALS. IF GAS VALVE OUTLET PRESSURE IS CORRECT THEN GOTO STEP 6. IF NO GAS
PRESSURE IS PRESENT AT THE GAS VALVE OUTLET; THEN REPLACE THE GAS VALVE.
6
THERE IS A BROKEN WIRE TO THE GAS VALVE OR
ONE OF THE GAS VALVE WIRES HAS A BAD
CONNECTION.
USE OHM (Ω)
METER TO DETERMINE WHICH WIRE TO THE GAS VALVE IS
DEFECTIVE.
REMOVE THE 9 PIN PLUG FROM THE CONTROL BOARD AND THE WIRES FROM THE GAS
VALVE. USE A OHM (Ω) METER TO DO A RESISTANCE TEST ON BOTH OF THE BROWN
WIRES FROM THE PIN ON THE 9 PIN PLU
G TO THE GAS VALVE. WHEN PREFORMING THIS
TEST MOVE THE WIRE HARNESS TO CHECK FOR A BAD CONNECTION. IF A CONNECTION
IS BAD THE METER READING WILL CHANGE FROM ZERO OHMS TO SHOWING OPEN OR
THE INFINITY (∞) SYMBOL. IF A WIRE IS FOUND TO BE DEFECTIVE OR HAS A BAD
CONNECTION; THEN REPLACE THE WIRE OR WIRE HARNESS. IF THE BOTH WIRES ARE
SHOWING CLOSE TO ZERO OHMS (Ω) THEN GOTO STEP 7.
7
CONTROL BOARD IS DEFECTIVE
USE A MICROAMP METER TO CHECK FOR CURRENT BETWEEN THE
FLAME SENSOR AND THE CONTROL BOARD. THE FLAME SENSOR
CURRENT MUST BE ABOVE 1 MICROAMP WHEN THERE IS A FLAME AT
THE SENSOR.
IF THE AMP METER VERIFIES THAT THE FLAME SENSOR CURRENT READING IS ABOVE 1
MICROAMP (0.000001 AMPS) ON THE YELLOW WIRE THAT IS ATTACHED TO THE 9 PIN
PLUG ON THE CONTROL BOARD WHEN THE BURNER FLAME IS PRESENT BUT THE
B
URNER WILL NOT STAY LIT; REPLACE THE CONTROL BOARD.
8
VENT ISSUES OR VENT DOWN DRAFT
IF THE BURNER DOES NOT LIGHT, LIGHTS BUT DOES NOT STAY LIT OR
RUMBLES WHEN LIT YOU MAY HAVE A VENT PROBLEM. USE A INCHES
OF WATER LOW PRESSURE TO MEASURE THE AMOUNT OF DRAFT IN
THE VENT PIPE. THIS CAN BE MEASURED AT THE PRESSURE PORT ON
THE TOP OF THE BURNER BOX.
THE DRAFT CAN BE MEASURED BY REMOVING TH
E BLACK HOSE FROM THE PRESSURE
SWI
TCH THAT EXTENDS TO THE TOP OF THE BURNER HOUSING AND CONNECT IT TO A
INCHES OF WATER PRESSURE GAUGE THAT READS BETWEEN +2.0 AND -2.0 INCHES OF
WATER (INWC). IF THE PRESSURE GAUGE READS A NEGATIVE PRESSURE OF 0.1 INCHES
OF WATER OR GREATER WHEN THE BURNER FLAME IS PRESENT THEN GO TO STEP 6. IF
THE PRESSURE GAUGE READS 0.0 IN
CHES OF WATER OR HAS A POSITIVE PRESSURE
READING
WHEN THE BURNER FLAME IS PRESENT THEN ADD A EXTENSION TO THE ROOF
JACK AS DESCRIBED IN THE INSTRUCTIONS.
MGD-B SERIES CONTROL BOARD
7
Heat Controller, Inc. MGD-B SERIES GAS FURNACE Owner’s Manual
G18D SERIES CONTROL BOARD
TROUBLE SHOOTING GUIDE
10
G18D Series Gas Furnace OWNER’S MANUAL
Mortex Products Inc. / Fort Worth, TX 76106
G18D Owner’s Manual
BURNER FLAME
CALL FOR HEAT
WILL NOT LIGHT
TWO FLASHS
PRESSURE SWITCH NOT CLOSING
USE VOLT METER TO CHECK FOR 24 VAC BETWEEN EACH OF THE
SWITCH CONTACTS AND THE 24 VAC COMMON (GROUND) OR REMOVE
THE ELECTRICAL WIRES AND USE A OHM METER TO CHECK ACROSS THE
SWITCH CONTACTS.
IF THE VOM INDICATED THERE IS 24 VAC BETWEEN ONLY ONE CONTACT AND COMMON
OR THE OHM METER READING WAS NOT NEAR ZERO OHMS AND THE COMBUSTION AIR
BOOST
ER MOTOR IS OPERATING; CHECK THE COMBUSTION AIR PROP FANS TO MAKE
SURE THEY ARE OK. IF THE FANS ARE OK THEN REPLACE THE PRESSURE SWITCH.
BROKEN WIRE OR BAD ELECTRICIAL CONNECTION
USE A OHM METER TO CHECK THE BLUE WIRES GOING TO THE
PRESSURE SWITCH FROM THE 9 PIN PLUG ON THE CONTROL BOARD.
REMOVE THE 9 PIN PLUG FROM THE CONTROL BOARD AND CONNECT THE OHM METER
TO EACH END OF THE WIRE. READING SHOULD BE CLOSE TO "0" OHMS. MOVE THE
WIRE, IF OHM READING CHANGES WHEN WIRE IS BEING MOVED THEN REPLACE THE
WIRE. CHECK BOTH BLUE WIRES TO THE PRESSURE SWITCH.
DEFECTIVE CONTROL BOARD
USE A VOLT METER TO CHECK FOR 24 VAC ON THE BLUE WIRES GOING
T
O THE 9 PIN PLUG ON THE CONTROL BOARD OR REMOVE THE
ELECTRICAL WIRES FROM THE CONTACTS AND USE A OHM METER
ACROSS THE CONTACTS TO DETERMINE IF THE SWITCH IS CLOSING.
LOOSTEN THE TERMINALS ON BOTH BLUE WIRES ON THE PRESSURE SWITCH TERMINALS
AND PLACE A JUMPER ACROSS THE SWITCH ONCE THE GAS BURNER HAS LIT. IF THE
UNIT DOES NOT CONTINUE TO OPERATE WITH THE JUMPER IN PLACE THEN REPLACE
T
HE CONTROL BOARD.
BURNER FLAME
CALL FOR HEAT
WILL NOT LIGHT
THREE FLASHS
PRESSURE SWITCH NOT OPENING
WITH COMBUSTION AIR BOOSTER MOTOR OPERATING; USE VOM TO
CHECK FOR 24 VAC BETWEEN EACH SWITCH CONTACT AND COMMON
(GROUND).
IF THE VOM INDICATED THERE IS 24 VAC BETWEEN BOTH CONTACTS AND COMMON
AND THE COMBUSTION AIR BOOSTER MOTOR IS NOT OPERATING; REPLACE THE
PRESSURE SWITCH.
CA
LL FOR HEAT
BURNER FLAME
WILL NOT LIGHT
FOUR FLASHS
OPEN LIMIT CONTROL
USE A VOLT METER TO CHECK FOR 24 VAC AT THE UPPER LIMIT
CONTROL AND THE PRIMARY LIMIT CONTROL.
TO CHECK THE VOLTAGE PLACE ONE PROBE OF THE VOLT METER ON THE TERMINAL OF
THE LIMIT CONTROL AND THE OTHER PROBE ON THE 24 VAC COMMON TERMINAL OR
ON GROUND. DO NOT REMOVE THE WIRES FROM THE TERMINALS ON THE LIMIT
CONTROLS JUST LOOSTEN THE QUICK CONNECT FITTING SO YOU CAN GET A READING. IF
THERE IS 24 VAC ON ONE TERMINAL ONLY THEN REPLACE THE LIMIT CONTROL. YOU
CAN CHECK THE LIMIT CONTROL WITH A OHM METER WITH THE WIRES REMOVED.
REPLACE THE LIMIT IF THE OHM CHECK INDICATED AN OPEN CIRCUIT.
NO CALL
FOR HEAT
BURNER FLAME
WILL NOT EXTINGUISH
FIVE FLASHS
GAS VALVE ENERGIZED WITH OUT A CALL FOR
HEAT.
USE A VOLT METER TO CHECK THE "W" TERMINAL ON THE CONTROL
BOARD TO DETERMINE IF A 24 VAC SIGNAL IS PRESENT.
I
F 24 VAC IS PRESENT ON THE "W" TERMINAL ON THE CONTROL BOARD CHECK FOR A
BAD THERMOSTAT OR A DEFECTIVE THERMOSTAT SUB BASE, OR A SHORTED
THERMOSTAT WIRE BETWEEN THE THERMOSTAT AND THE CONTROL BOARD.
NO CALL FOR HEAT (NO VOLTAGE ON THE "W"
TERMINAL ON THE CONTROL BOARD) THE GAS
VALVE IS ENERGIZED AND THE BURNER FLAME IS
STILL PRESENT.
USE A VOLT METER TO CHECK THE GAS VALVE TERMINALS TO
DETERMINE IF
24 VAC IS PRESENT AT THE GAS VALVE ELECTRICAL
TERMINALS.
IF 24 VAC IS PRESENT AT THE TERMINALS AND REMOVING THE BROWN ELECTRICAL
WIRES FROM THE GAS VALVE TERMINALS EXTINGUISHES THE BURNER FLAME THEN LET
THE FURNACE COOL DOWN AND REPLACE THE CONTROL BOARD.
NO CALL FOR HEAT, BUT THE BURNER FLAME IS
STILL PRESENT.
USE A VOLT METER TO CHECK THE GAS VALVE TERMINALS TO
DETERMINE IF 24 VAC IS PRESENT AT THE GAS VALVE ELECTRICAL
T
ERMINALS.
IF 24 VAC IS NOT PRESENT AT THE TERMINALS AND REMOVING THE BROWN ELECTRICAL
WIRES FROM THE GAS VALVE TERMINALS DOES NOT EXTINGUISHTHE BURNER FLAME;
TURN THE VALVE IN THE GAS LINE TO THE OFF POSITION AND LET THE FURNACE COOL
DOWN; THEN REPLACE THE GAS VALVE.
MGD-B SERIES CONTROL BOARD
8
04/2009
07/2009
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