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LDAP-IOM (01-22) 207733-A
Table 19. General Troubleshooting
Symptom
Probable Cause
Remedy
Venter
motor will
not start
1 . No power to unit
Turn ON power and check supply fuses or circuit breaker
2 . No 24V power to integrated circuit board Turn up thermostat
Check control transformer output
3 . Integrated circuit board fuse blown
Correct cause and replace fuse (3A, type ATC or ATO, 32VDC)
4 . No power to venter motor
Tighten connections at circuit board and/or motor terminals
5 . Integrated circuit board defective
Replace integrated circuit board
6 . Defective venter motor
Replace venter motor (refer to
Venter Motor and Wheel Assembly
section)
Burner will
not light
1 . Manual valve not open
Open manual valve
2 . Air in the gas line
Bleed gas line (initial startup only)
3 . Gas pressure too high or too low
Supply pressure should be 5–14 IN WC for natural gas or 11–14 IN WC for
propane
4 . No spark
Perform following:
a . Loose wire connections
Ensure that all wire connections are solid
b . Transformer failure
Ensure that 24V power is available
c . Incorrect spark gap
Maintain spark gap at 1/8 inch
d . Spark cable shorted to ground
Replace worn or grounded spark cable
e . Spark electrode shorted to ground
Replace ceramic spark electrode if it is cracked or grounded
f . Burner not grounded
Ensure that integrated circuit board is grounded to ignitor
g . Circuit board not grounded
Ensure that integrated circuit board is grounded to furnace chassis
h . Unit not properly grounded
Ensure that unit is properly field grounded to earth ground and properly phased
(L1 to hot lead L2 to neutral)
i . Integrated circuit board fuse blown
Correct cause and replace fuse (3A, type ATC or ATO, 32VDC)
j . Faulty integrated circuit board
If 24V power is available to integrated circuit board and all other causes have
been eliminated, replace board
5 . Lockout device interrupting control
circuit by above causes
Reset lockout by interrupting control at thermostat or main power
6 . Heat section pressure switch(es) not
closing
Perform following:
Ensure that unit is properly vented
Remove obstruction(s) from vent
Replace faulty tubing to pressure switch
7 . Faulty heat section pressure switch
Replace pressure switch
8 . Main valve not operating
Perform following:
a) Defective valve
If 24V power is measured at valve connections and valve remains closed,
replace valve
b) Loose wire connections
Check and tighten all wiring connections
9 . Integrated circuit board does not
power main valve
Perform following:
a) Loose wire connections
Ensure that all wire connections are solid
b) Flame sensor grounded
Ensure that flame sensor lead is not grounded or that sensor insulation or
ceramic is not cracked—replace as required
c) Incorrect gas pressure
Supply pressure should be 5–14 IN WC for natural gas or 11–14 IN WC for
propane
d) Cracked ceramic at sensor
Replace sensor
Burner
cycles ON
and OFF
1 . Gas pressure too high or too low
Supply pressure should be 5–14 IN WC for natural gas or 11–14 IN WC for
propane
2 . Burner not grounded
Ensure that integrated circuit board is grounded to ignitor
3 . Circuit board not grounded
Ensure that integrated circuit board is grounded to furnace chassis
4 . Faulty integrated circuit board
If 24V power is available to integrated circuit board and all other causes have
been eliminated, replace board
5 . Heat section pressure switch(es) not
closing
Perform following:
Ensure that unit is properly vented
Remove obstruction(s) from vent
Replace faulty tubing to pressure switch
6 . Faulty heat section pressure switch
Replace pressure switch
7 . Flame sensor grounded
Ensure that flame sensor lead is not grounded or that sensor insulation or
ceramic is not cracked—replace as required
8 . Cracked ceramic at sensor
Replace sensor
9 . Incorrect polarity
Reverse line volt leads to integrated circuit board