Lennox G21Q Series Installation Instructions Manual page 22

CONTINUED FORM
YES
UNIT WILL NOT RUN
FLOW CHART ON
PREVIOUS PAGE
HAS L.P. CONVERSION KIT
BEEN INSTALLED?
IF NOT, INSTALL KIT.
BLEED AIR BUY RUNNING UNIT THROUGH SEVERAL
TRIES FOR IGNITION. BREAK & REMAKE THERMOSTAT
DEMAND TO RESTART IGNITION SEQUENCE AT 2 TO 3
CHECK FOR LEAKS IN GAS SUPPLY
CAUTION—DO NOT USE MATCH OR FLAME
CHECK GAS SUPPLY LINE PRESSURE
IS PRESSURE WITHIN UNIT NAMEPLATE LISTING?
CORRECT
GAS PRESSURE.
REPLACE GAS VALVE.
TURN OFF POWER.
REMOVE & CHECK SPARK PLUG (USE 3/4” SPARK PLUG SOCKET).
1. WAS PLUG TIGHT WHEN REMOVED?
2. ARE CRACKS PRESENT IN PORCELAIN?
3. IS PLUG GAPPED PROPERLY?
10
4. REPLACE AND/OR REGAP PLUG IF REQUIRED.
PUT PLUG BACK IN UNIT. TURN ON POWER.
(LEAVE GAS OFF) & RETEST FOR SPARK.
REPLACE AIR INTAKE CHAMBER COVER. TURN ON GAS & RESTART UNIT.
G21 TROUBLESHOOTING FLOW CHART
(continued form flow chart on previous page)
NOTE—Numbered steps refer to illustrations on next to last page.
GAS
CHECKS
IS GAS SUPPLY NATURAL OR L.P.?
L.P.
NATURAL
IS GAS SUPPLY ON?
1. CHECK SUPPLY VALVE.
2. CHECK STOP VALVE AT UNIT.
3. CHECK MANUAL LEVER OR
SWITCH ON GAS VALVE IN UNIT.
AIR IN GAS PIPING?
MINUTE INTERVALS.
PIPING & REPAIR IF NEEDED.
TO CHECK FOR GAS LEAKS.
NO YES
IS GAS VALVE ACTUALLY OPENING?
DETERMINE BY CHECKING FOR MANIFOLD
PRESSURE DURING TRIALS FOR IGNITION.
NO YES
SPARK CHECKS
CAUTION—HIGH VOLTAGE
CHECK FOR LEAKS IN UNIT MANIFOLD PIPING.
LEAKS
REPAIR LEAKS
& RETEST.
VISUALLY CHECK OUTSIDE TERMINATIONS OF
INTAKE & EXHAUST PVC PIPING FOR OBSTRUCTIONS.
VISUALLY CHECK CONDENSATE DRAIN FOR OBSTRUCTIONS.
REFER TO INSTALLATION INSTRUCTIONS: ARE IN-
TAKE & EXHAUST LINES PROPERLY SIZED & APPLIED
WITHIN LENGTH, DIAMETER & ELBOW LIMITS?
CORRECT PIPING
ERRORS & RET-
EST.
(USE CARE TO PREVENT DAMAGE TO COVER GASKET).
9
IS 120VAC PRESENT BETWEEN
JP1--6 AND JP1--5?
YES
CHECKOUT
WIRING
CONNECTIONS
& REPAIR.
TO CHECK FOR SPARK, USE EXTERNAL PLUG CONNECTED
TO SPARK WIRE. MAKE SURE SPARK GROUND STRAP
IS FIRMLY GROUNDED TO UNIT.
DANGER—SHOCK HAZARD. TURN OFF GAS SUPPLY BEFORE TESTING.
DO NOT HANDLE SPARK PLUG OR WIRE DURING TEST.
RESTART IGNITION SEQUENCE
(BREAK & REMAKE THERMOSTAT DEMAND).
AFTER 30 TO 35 SECONDS PRE--PURGE, IS SPARKING PRESENT
FOR APPROXIMATELY 7 SECONDS DURING IGNITION TRIAL?
YES
CHECK FOR IGNITION WIRE(FOR BREAKS OR SHORTS TO GROUND)
& FOR LOOSE CONNECTIONS TO CONTROL AND/OR SPARK PLUG.
BREAK & REMAKE THERMOSTAT DEMAND
SPARK
3DJH 
NO LEAKS
NO YES
CHECKS
TURN OFF GAS TO UNIT.
REMOVE AIR INTAKE CHAMBER COVER
CHECK PURGE BLOWER FOR BINDING
OR MECHANICAL DAMAGE.
BREAK & REMAKE THERMOSTAT DEMAND
TO INITIATE CONTROL SEQUENCE.
IS120VAC PRESENT ACROSS PURGE
8
BLOWER MOTOR TERMINALS?
NO YES
DOES PURGE BLOWER RUN?
YES
NO
PURGE BLOWER.
REPLACE
PRIMARY CONTROL.
NO
MAKE OHMMETER CHECK.
TO INITIATE CONTROL SEQUENCE.
NO SPARK
REPLACE
PRIMARY CONTROL.
AIR
NO
REPLACE