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SERVICING
CHECKING FOR DELAYED IGNITION
Delayed ignition is a delay in lighting a combustible mixture
of gas and air which has accumulated in the combustion
chamber.
When the mixture does ignite, it may explode and/or rollout
causing burning in the burner venturi.
If delayed ignition should occur, the following should be
checked. Furnace design makes this extremely unlikely un-
less safety controls have been by-passed or tampered with.
Never by-pass or alter furnace controls.
1. Improper gas pressure - adjust to proper pressure
2. Improper burner positioning - burners should be in locating
slots, level front to rear and left to right.
3. Carry over (lighter tube or cross lighter) obstructed - clean.
4. Main burner orifice(s) deformed, or out of alignment to
burner - replace.
CHECKING INTEGRATED IGNITION CONTROL
BOARDS
NOTE: Failure to earth ground the furnace, reversing the
neutral and hot wire connection to the line (polarity), or a
high resistance connection in the neutral line may cause the
control to lockout due to failure to sense flame.
T
O AVOID THE RISK OF ELECTRICAL SHOCK, WIRING TO THE UNIT
MUST BE PROPERLY POLARIZED AND GROUNDED.
BEFORE PERFORMING SERVICE LISTED BELOW.
The ground wire must run from the furnace all the way back
to the electrical panel. Proper grounding can be confirmed by
disconnecting the electrical power and measuring resistance
between the neutral (white) connection and the burner closest
to the flame sensor. Resistance should be less than 2 ohms.
The ignition control is a combination electronic and electro-
mechanical device and is not field repairable. Complete unit
must be replaced.
L
INE VOLTAGE NOW PRESENT
These tests must be completed within a given time frame due
to the operation of the ignition control. The trial for ignition
period is 4 seconds.
The ignition control is capable of diagnosing many furnace
failures to help in troubleshooting. The control utilizes a dual,
7-segment LED display to indicate diagnostic codes.
When the control is powered up normally the light will be on
continuously. The display will indicate "ON" when powered
and in standby mode. This can be used to test for 120 volts
and 24 volts to the control since both must be present for
the light to be on. If this step fails, check for 120 volts to the
control and check the transformer and its associated wiring.
WARNING
D
ISCONNECT POWER
WARNING
If this step is successful give the control a call for heat and
wait five (5) seconds or until the furnace goes into lockout. If
the control detects a failure it will now be shown on the diag-
nostic indicator light/display. Refer to the Abnormal Operation
section in the Sequence of Operation section of this manual
for more detail on failure codes.
1. Check for 120 volts from Line 1 (Hot) to Line 2 (Neutral)
at the ignition control. No voltage, check the door switch
connections and wire harness for continuity.
2. With the thermostat calling for heat, check for 24 volts
from W1 to C terminal on the ignition control. No voltage.
Check transformer, room thermostat, and wiring.
If you have 24 volts coming off the transformer but receive
approximately 13 volts on the terminal board between (C)
and (R), check for blown fuse.
3. Check for 120 volts to the induced draft blower (low-stage)
by measuring voltage between Pin 3 and Pin 4 (on the
5-pin connector) located on circuit board. No voltage,
check for loose connection in the 5-pin connector or re-
place ignition control.
Check for 120 volts to the induced draft blower (high-
stage) by measuring voltage between Pin 2 and Pin 4 (on
the 5-pin connector) located on circuit board. No voltage,
check for loose connection in the 5-pin connector, no call
for high stage heat or replace ignition control.
4. If voltage is present in Steps 1 through 3 and the induced
draft blower is operating, check for 120 volts to the igniter
during the preheat cycle. Measure voltage between Pin
1 and Pin 5 (on the 5-pin connector) located on ignition
control. No voltage, check low stage and high stage pres-
sure switches or replace the ignition control board.
5. After the igniter warm-up time, begin checking for 24 volts
to the gas valve. Voltage will be present for seven seconds
only if proof of flame has been established.
6. If proof of flame was established voltage will be provided
to the air circulation blower following the heat on delay
period.
a. BEFORE replacing the ECM motor assembly or the
end bell, first check the motor with a Goodman #UTT-
01 UltraCheck-EZ
with the diagnostic tool, the motor is good. To check
the end bell, see the previous variable speed testing
section of this manual before replacing the end bell.
b. The two-stage variable speed furnaces should have
120 Volts at the motor at all times, even without a
call for cooling or heating. These motors receive their
operational signals through the 4-pin wiring harness,
connected between the motor and integrated control
board.
diagnostic tool. If the motor runs
TM
67
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