OWNER S MANUAL Manufactured Home Downflow Gas Furnace: MGD-B Series

OWNER S MANUAL Manufactured Home Downflow 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. 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 off 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 Continuous Blower On cooling / heating thermostats with a AUTO / ON fan switch, when the fan switch is set to the ON position, 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 switches 115 VAC to the COOL terminal on the control board and the motor runs on the selected blower motor speed tap. Intermittent Blower - Cooling On cooling / heating thermostats with a AUTO / ON fan switch, when the fan switch is set to the AUTO position and the thermostat calls for cooling, 24 VAC is sent from the red thermostat wire to the green thermostat wire and the yellow thermostat wire. The green thermostat wire will energize the blower motor cooling fan terminal ( G Terminal) on the 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. Intermittent Blower - Heating On cooling / heating thermostats with an AUTO / ON fan switch, when the fan switch is set to the AUTO position and the thermostat calls for heating, 24 VAC is switched from the red thermostat wire to the white thermostat wire. The control board has a programmed time delay period that will place 115 VAC on the HEAT terminal on the control board at the completion of the time delay and allow the blower motor run on the selected blower 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 software that the limit circuit is closed. The control board software then checks for a 24 VAC signal from the pressure switch. If the pressure switch is open the software checks the flame sensor to determine if a flame is present. If no flame is present then the software places the control board into the ready mode which is indicated by a steady green diagnostic indicator light. NOTE: If a limit is open when the line power (115 VAC) is turned on; the control board software 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 diagnostic led will flash four flashes. NOTE: If the pressure switch electrical contacts are stuck closed nothing will happen until there is a call for heat. Upon a call for heat the control board software will wait 30 seconds for the pressure switch electrical contacts to open. During this time, none of the components will operate. After 30 seconds the diagnostic indicator led will flash two flashes and none of the components will operate. Heating Cycle When the thermostat switch is set to the HEAT position, the thermostat fan switch is set to the AUTO position 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 software there is a call for heat. The control board switches 115 VAC to the black wires on the 6 pin plug located at the bottom right side of the control board, energizing the combustion air booster motor. 3

Heat Controller, Inc. MGD-B SERIES GAS FURNACE Owner s Manual The combustion air booster motor is located inside the white plastic assembly attached to the 4 round galvanized pipe. When the combustion 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 negative pressure at the top of the booster motor assembly and a positive pressure at the burner box. A tube is attached to the pressure port at the top of the booster motor assembly and the top of the burner box that extends to the pressure ports on the pressure switch, providing the negative and positive pressures to the switch. If the pressures applied to the positive and negative ports (Differential 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 attached to the 9 pin plug indicating to the control board software the pressure switch has closed. When the pressure switch has closed the control board starts a 30 second ignition warm up. This gives the hot surface igniter 30 seconds to obtain its normal operating temperature. After the 30 second ignition 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 will open the gas valve and start the flow of gas. The hot surface igniter should ignite the flow of gas and start the flame stabilization period. During the flame stabilization 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 software that a flame is present. The indoor blower time delay will start a 50 second on delay after the flame stabilization 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 heating mode. The furnace will continue to operate until the call for heat from the thermostat has been satisfied. At this point the gas valve solenoid will be de-energized, the burner flame will be extinguished and the control board software 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 diagnostic indicator indicating the control board is ready to resume normal operation. Ignition Retry If the burner flame has not been established or has been interrupted when the thermostat is calling for heat; the control board will start the ignition retry operation. During the retry operation the combustion air booster motor will continue to operate. The control will start a 15 second purge to vent any unburned gas from the heat exchanger. The igniter warm-up period is extended to 27 seconds then, 24 VAC is sent to the gas valve solenoid opening the solenoid and starting the flow of gas. If a flame is established for more than 10 seconds during the retry the unit will continue to operate normally and the control board will clear the ignition retry counter. If a flame has not been established then the control board will advance the retry counter and will continue the ignition retry operation. The ignition retry operation will attempt to re-ignite the gas burner a total of three ignition cycles during a call for heat from the thermostat. If the burner flame has not been established after the third ignition retry cycle the control board will go into a soft lockout for a period of one hour. If there is still a call for heat after the one hour lockout the furnace will initiate a normal start cycle. If the problem has not been corrected the furnace will lockout again after the three ignition 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 operation the control board will clear the ignition retry counter, will clear a soft 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 removed the 24 VAC signal to the gas valve solenoid will be removed. If the control board software indicates a microamp signal is present at the flame sensor indicating a flame is present the control board will keep 115 VAC present to the combustion air booster motor, 115 VAC to the heat terminal for the indoor fan to keep the indoor fan motor energized and will flash a error code of 5 flashes indicating a flow of gas with no call for heat. The furnace will continue to operate at this condition until the gas flow has been interrupted and the flame has been extinguished. OBSERVING BURNER OPERATION 1. Observe burner to make sure it ignites and to observe the flame color. With Natural gas, the flame will be blue with yellow tips; with Propane gas, a yellow flame can be expected. 2. Allow furnace to heat up until 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 abnormalities should occur, such as the burner failing to light or to turn off, the flame looks sooty or it seems to be floating around inside the heat exchanger, call a qualified service technician for service. Mortex Products Inc. / Fort Worth, TX 76106 G18D Owner s Manual 4 4

Owner s Manual MGD-B SERIES GAS FURNACE Heat Controller, Inc. 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 filters are clean, supply registers are open and return air grilles are not obstructed. 6. Be sure that furnace flue 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 flashes 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. Four Flashes: Limit switch is open. Five Flashes: Gas valve energized or flame sensed at flame 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 off position; call a qualified service technician or your gas supplier. DO NOT ATTEMPT TO REPAIR THE APPLIANCE YOURSELF. 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 off. 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 qualified 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 sufficient heat has built up inside the furnace. Gas Valve - The gas valve for all models are 100% shut-off type and will fail safe if for some reason the gas is turned off. INSPECTION AND MAINTENANCE BY THE HOMEOWNER Make a visual inspection of the furnace every 30 days. Do the following: Filters- Clean filters 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 floor. DO NOT cover or obstruct these floor 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 off 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 inefficient burner operation. If excessive ice has formed on the inlet or exhaust portions of the roof jack, it must be carefully removed. Mortex Products Inc. / Fort Worth, TX 76106 5 5

Heat Controller, Inc. MGD-B SERIES GAS FURNACE Owner s Manual MGD-B G18D SERIES CONTROL BOARD TROUBLE SHOOTING GUIDE PRE-TROUBLESHOOTING CHECK LIST YOU MUST HAVE THE FOLLOWING TOOLS TO PREFORM THE TROUBLESHOOTING DESCRIBED BELOW: 1 - VOLT, AMP, OHM METER VOLTAGE RANGE 0-300 VOLTS 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 VISE GRIP PLIERS 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 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 READING IS BETWEEN 1.0-3.7 MICROAMPS (0.000001-0.0000037 AMPS) GOTO STEP 4; IF THE BURNER FLAME SENSOR CURRENT IS 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 MICROAMPS (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. 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 FRONT 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 5 THERE IS A BROKEN WIRE TO THE GAS VALVE OR ONE OF THE GAS VALVE WIRES HAS A BAD CONNECTION. CONTROL BOARD IS DEFECTIVE USE OHM (Ω) METER TO DETERMINE WHICH WIRE TO THE GAS VALVE IS DEFECTIVE AND REPLACE THE WIRES. 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. 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 SHOWING CLOSE TO ZERO OHMS (Ω) THEN GOTO STEP 5. IF THE BURNER FLAME SENSOR CURRENT READING IS BETWEEN 1.0-3.7 MICROAMPS (0.000001-0.0000037 AMPS) AND THE BURNER WILL NOT STAY LIT THEN REPLACE THE CONTROL BOARD ONLY IF THE CHECKS IN STEPS 1, 2, 3, AND 4 HAVE BEEN PREFORMED. 6

Owner s Manual MGD-B SERIES GAS FURNACE Heat Controller, Inc. CALL FOR HEAT BURNER FLAME WILL NOT LIGHT ONE FLASH 1 2 3 4 5 6 7 8 MGD-B G18D SERIES CONTROL BOARD TROUBLE SHOOTING GUIDE 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. 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. BAD OR BROKEN IGNITER NO GAS LINE PRESSURE AT THE GAS VALVE GAS VALVE SOLINOID NOT OPENING 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. 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 WATER (INWC) FOR NATURAL GAS OR 11.0 INCHES OF WATER (INWC) FOR PROPANE GAS. 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 ELECTRICAL 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. 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. 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. 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. 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. 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. 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. 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. 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 TERMINALS. 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. 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 SHOWING CLOSE TO ZERO OHMS (Ω) THEN GOTO STEP 7. 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 BURNER WILL NOT STAY LIT; REPLACE THE CONTROL BOARD. THE DRAFT CAN BE MEASURED BY REMOVING THE BLACK HOSE FROM THE PRESSURE SWITCH 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 INCHES 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. 7

Heat Controller, Inc. MGD-B SERIES GAS FURNACE Owner s Manual BURNER FLAME CALL FOR HEAT WILL NOT LIGHT TWO FLASHS BURNER FLAME CALL FOR HEAT WILL NOT LIGHT THREE FLASHS CALL FOR HEAT BURNER FLAME WILL NOT LIGHT FOUR FLASHS NO CALL FOR HEAT BURNER FLAME WILL NOT EXTINGUISH FIVE FLASHS MGD-B G18D SERIES CONTROL BOARD TROUBLE SHOOTING GUIDE 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. 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. DEFECTIVE CONTROL BOARD USE A VOLT METER TO CHECK FOR 24 VAC ON THE BLUE WIRES GOING TO 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. PRESSURE SWITCH NOT OPENING WITH COMBUSTION AIR BOOSTER MOTOR OPERATING; USE VOM TO CHECK FOR 24 VAC BETWEEN EACH SWITCH CONTACT AND COMMON (GROUND). OPEN LIMIT CONTROL USE A VOLT METER TO CHECK FOR 24 VAC AT THE UPPER LIMIT CONTROL AND THE PRIMARY LIMIT CONTROL. 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. 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. 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 TERMINALS. 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 BOOSTER 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. 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. 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 THE CONTROL BOARD. 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. 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. IF 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. 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. 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. 8

07/2009