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IMPORTANT
The following
service procedures
are provided
as a general guide. Follow appliance
manufac-
turer's service instructions
if available.
On lockout and retry models, meter readings be-
tween gas control and ignition module must be
taken within the trial for ignition period. Once the
ignition module shuts off, lockout models must
be reset by setting the thermostat
down for at
least one minute
before
continuing.
On retry
models, wait for retry or reset at the thermostat.
lf any component
does not function
properly,
make sure it is correctly
installed
and wired
before replacing it.
The ignition
module
cannot
be repaired.
If it
malfunctions,
it must be replaced.
Only trained,
experienced
service technicians
should service intermittent
pilot systems.
Perform the checkout on page 14 as the first step in
troubleshooting.
Then
check
the
appropriate
trou-
bleshooting
guide
(Fig. 15 or 16) and the schematic
diagram
(Figs. 17-22) to pinpoint the cause of the prob-
lem. If troubleshooting
indicates an ignition problem, see
Ignition System Checks below to isolate and correct the
problem.
Following troubleshooting,
perform the checkout
pro-
cedure (page 14) again to be sure system is operating
normally.
IGNITION SYSTEM CHECKS
STEP 1: Check ignition cable.
Make sure:
0
Ignition cable does not run in contact with any metal
surfaces.
0
Ignition cable is no more than 36 in. [0.9 m] long.
0 Connections
to the ignition module and to the igniter or
igniter-sensor
are clean and tight.
0
Ignition cable provides good electrical continuity.
STEP 2: Check
ignition
system
grounding.
Nuisance
shutdowns
are often caused
by a poor
or erratic
ground.
0 A common ground, usually supplied by the pilot burner
bracket, is required for the module and the pilot burner/
igniter sensor.
l
Check for good metal-to-metal
contact between
the pilot burner bracket and the main burner.
l
Checkthe
ground lead from the GND(SURNER)
terminal
on the module to the pilot burner. Make
sure connections
are clean and tight. If the wire is
damaged or deteriorated,
replace it with No. 14-l 8
gauge, moisture-resistant,
thermoplastic
insulated
wire with 105O C [221" F] minimum rating.
-
Check the ceramic
flame rod insulator for
cracks or evidence of exposure to extreme heat,
which can permit leakage
to ground.
Replace
pilot burner/igniter-sensor
and provide shield if
necessary.
-lf
flame rod or bracket are bent out of posi-
tion, restore to correct position.
STEP 3: Check spark ignition circuit.
You will need a
short jumper
wire made from ignition
cable or other
heavily insulated
wire.
0 Close the manual gas valve.
0 Disconnect
the ignition cable at the SPARK terminal
on the module.
When performing the following steps, do not
touch stripped end of jumper or SPARK terml-
nal. The ignitlon circuit generates over 10,000
volts and electrlcal shock can result.
0
Energize the module and immediately
touch one end
of the jumper firmly to the GND terminal on the module.
Move the free end of the jumper
slowly
toward
the
SPARK terminal until a spark is established.
0
Pull the jumper slowly away from the terminal and note
the length of the gap when sparking stops. Check table
below.
ARC LENGTH
No arc or arc less
than l/8 in. [3 mm]
ACTION
Check external fuse, if
provided.
Verify power at module
input terminal.
Arc l/8 in. [3 mm]
or longer.
Replace module if fuse
and power okay.
Voltage output is okay
STEP 4: Check pilot and main burner lightoff.
0
Set the thermostat
to call for heat.
0 Watch the pilot burner during the ignition sequence.
See if:
l
Ignition spark continues
after the pilot is lit.
l
The pilot lights and the spark stops, but main
burner does not light.
l
S86OOB,H,M;S8610B,H;S8660D;S8670Donly:
The pilot lights, the spark stops and main burner
lights, but the system locks out.
0
lf so, ensure adequate
flame current as follows.
l
Turn off furnace at circuit breaker or fuse box.
l
Clean the flame rod with emery cloth.
l
Make sure electrical connections
are clean and
tight. Replace damaged wire with moisture-resistant
No. 18 wire rated for continuous
duty up to 105" C
[221" q.
l
Check for cracked ceramic insulator, which can
cause short to ground, and replace igniter-sensor
if
necessary.
l
At the gas control, disconnect
main valve wire
from the TH or MV terminal.
17
68-0085-2
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