Troubleshooting And Service - Honeywell S89C Manual

TROUBLESHOOTING AND SERVICE

------------------------ IMPORTANT- - -----------------------
1. The following service procedures are provided as
a general guide. Follow appliance manufac­
turer's service instructions if available.
2. All meter readings must be taken within the trial
for ignition period. Once the ignition period ends,
the system must be reset by setting the thermo­
stat down for at least 45 sec. 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 mal­
functions, it must be replaced.
5. Only trained, experienced service technicians
should service direct ignition systems.
Perform the checkout steps on page 11 as the first step
in troubleshooting. Then check the troubleshooting guide
(Fig. 13) and the schematic diagram (Fig. 14) to pinpoint
the cause of the problem.
Following troubleshooting, perform the checkout pro­
cedure (page 11) again to be sure system is operating
normally.
IGNITION SYSTEM CHECKS
STEP 1: Check igniter wire harness.
Make sure:
□ Ignition wire does not touch any metal surface.
□ Connections to the module and the igniter-sensor are
clean and tight.
□ Ignition wire provides good electrical continuity.
STEP 2: Check ignition system grounding. Nuisance
shutdowns are often caused by a poor or erratic ground.
□ A common ground is required for the module, igniter,
flame sensor and main burner.
— Check for good metal-to-metal contact between
the igniter bracket and the main burner.
— Checkthe ground lead from the GND (BURNER)
terminal on the module to the igniter bracket. 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° С [2 2 Г F] minimum rating. Use a
shield if necessary to protect the ground wire from
radiant heat.
— Check temperature at the igniter ceramic or
flame sensor Insulator. Excessive temperature will
permit leakage to ground. Provide shield if tempera­
ture exceeds rating of igniter or sensor.
— If flame sensor or bracket is bent out of position,
restore to correct position.
— Replace igniter and sensor or igniter-sensor with
identical unit if insulator is cracked.
STEP 3: Check flame sensing circuit.
□ Make sure burner flame is capable of providing a good
rectification signal. See Fig. 11.
□ Make sure about 3/4 to 1 in. of the flame sensor or
igniter-sensor is continuously immersed in the flame for
best flame signal. See Fig. 11. Bend the bracket or flame
sensor, or relocate the sensor as necessary. Do not
relocate an igniter or combination igniter-sensor.
□ Check for excessive (over 1000° F [538° C]) tempera­
ture at ceramic insulator on flame sensor. Excessive
temperature can cause short to ground; move sensor to
cooler location or shield insulator. Do not relocate an
igniter or combination igniter-sensor.
□ Check for cracked igniter-sensor or sensor ceramic
insulator, which can cause short to ground, and replace
unit 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° С
[221° F],
□ If the igniter is other than a Norton 201 or 271, make
sure it meets the following specifications.
• Igniter must reach 1000° С [1832° F] within 36
seconds with 102 Vac applied.
• igniter must maintain at least 500 M ohms insula­
tion resistance between the igniter leadwires and the
igniter mounting bracket.
• Igniter must not develop an insulating layer on its
surface (overtime) which would prevent flame sens­
ing.
• Igniter surface area immersed in flame must not
exceed 1/4 of the grounded area immersed inflame.
This would prevent flame sensing.
• Igniter current draw at 132 Vac must not exceed
5 A.
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