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Important
1. The following service procedures are provided as a general
guide.
2. Meter readings between gas control and ignition module must
be taken within the trial for ignition period. Once the ignition
module locks out, the system must be reset by turning the valve
off for at least one minute before continuing.
3. If any component does not function properly, make sure it is
correctly installed and wired before replacing it.
4. The ignition module cannot be repaired. If it malfunctions, it
must be replaced.
5. Only trained, experienced service technicians should service
intermittent pilot systems.
Perform the CHECKOUT steps on page 15 as the first step in
troubleshooting. Then check TROUBLESHOOTING GUIDE to
pinpoint the cause of the problem. If troubleshooting indicates an
ignition problem, see Ignition System Checks below to isolate and
correct the problem.
Following troubleshooting, perform the CHECKOUT procedure
(page 15) again to be sure system is operating normally.
Ignition System Checks
Step 1: Check ignition cable.
Make sure:
A. Ignition cable does not touch any metal surfaces.
B. Ignition cable is no more than 36 inches long.
C. Connections to the ignition module and to the igniter-sensor
are clean and tight.
D. Ignition cable provides good electrical continuity.
Step 2: Check ignition system grounding.
Nuisance shutdowns are often caused by a poor or erratic
ground.
A. A common ground, usually supplied by the pilot burner bracket,
is required for the module and the pilot burner/igniter sensor.
• Check for good metal-to-metal contact between the pilot
burner bracket and the main burner.
• Check the ground lead from GND (BURNER) 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. 14-18 gauge, moisture-resistant, thermoplastic
insulated wire with 105 C (221 F) minimum rating.
• If flame rod or bracket are bent out of position, restore to
correct position.
• Replace pilot burner/igniter sensor if insulator is cracked.
Step 3: Check spark ignition circuit. You will need a short jumper
wire made from ignition cable or other heavily insulated
wire.
A. Close the manual gas valve.
B. Disconnect the ignition cable at the SPARK terminal on the
module.
Page 18
TROUBLESHOOTING
When performing the following steps, do not touch stripped end of
jumper or SPARK terminal. The ignition circuit generates 13,000
volts at 25 pf load and electrical shock can result.
C. Energize the module and immediately touch one end of the
D. Pull the jumper slowly away from the terminal and note the
No arc or arc less than
1/8 inch
Arc 1/8 inch or longer
Step 4: Check pilot flame current.
A. Turn off furnace.
B. Disconnect main valve wire from the TH or MV terminal on the
C. Disconnect ground wire from GND (BURNER) terminal at
D. Connect a meter (dc microamp scale) in series with the ground
E. Turn valve on to call for heat. The spark will light the pilot but
F. Read the meter. The flame sensor current must be steady and
G. If the reading is less than the minimum or unsteady,
H. Remove meter and reconnect all wires. Return system to normal
WARNING
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.
length of the gap when sparking stops. Check table below.
ARC LENGTH
Check external fuse, if provided.
Verify power at module input terminal.
Replace module if fuse and power
okay.
Voltage output is okay.
gas control.
module.
lead.
• Disconnect ground lead from GND terminal on ignition module.
• Connect the black (negative) meter lead to the ignition module
GND (BURNER) terminal.
• Connect the red (positive) meter lead to the free end of the
ground lead.
the main burner will not light because the main valve actuator
is disconnected.
at least 1.0 uA.
• Make sure pilot flame envelopes 3/8 to 1/2 inch of the flame
rod.
• If necessary, adjust pilot flame by turning the pilot adjustment
screw on the gas control clockwise to decrease or counter-
clockwise to increase pilot flame. Following adjustment,
always replace pilot adjustment cover screw and tighten
firmly to assure proper gas control operation.
• Check for cracked ceramic insulator, which can cause short
to ground, and replace igniter-sensor if necessary.
• 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 F).
operation before leaving job.
ACTION
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