Form I-X, P/N 150491 R7, Page 21
Ignition Controller - As part of the intermittent safety pilot systems, the ignition con-
troller provides the high voltage spark to ignite the pilot gas and also acts as the ame
safety device. After ignition of the pilot gas, the ignition controller electronically senses
the pilot ame. A low voltage DC electrical signal is imposed on the separate metal
probe in the pilot assembly. The metal probe is electrically insulated from ground. The
pilot ame acts as a conduction path to ground completing the DC circuit and proving
pilot ame. Proper operation of the electronic spark ignition system requires a
minimum ame signal of .2 microamps as measured by a microampmeter. With
pilot ame proven, the ignition controller energizes the main gas valve.
CAUTION: Due to high voltage on pilot spark wire and pilot electrode, do
not touch when energized. See Hazard Levels, page 2.
If no spark occurs, check the following:
a) Voltage between Terminals TH and 7 should be at least 20 volts and no higher
than 32 volts. Refer to Troubleshooting (Paragraph 10.3) if no voltage is observed.
b) Short to ground in the high tension lead and/or ceramic insulator.
c) Pilot spark gap should be approximately 7/64".
Service NOTE: If replacing an earlier style of ignition controller, order replacement
kit P/N 257472 for a unit with recycling gas control Option AH2 or P/N 257473 for
Option AH3 gas control with lockout. (Option codes are listed on the unit wiring
diagram.)
Use of an optional vent damper requires an ignition controller with lockout.
Ignition Controller
with Lockout,
UTEC 1003-514,
P/N 257010, for
Option AH3 Gas
Control
Recycling Ignition
Controller, UTEC
1003-638A, P/N
257009, for Option
AH2 Gas Control
FIGURE 22 - Ignition
Controllers
NOTE: When checking
for spark with the pilot
burner assembly removed
from the burner rack, the
pilot assembly must be
grounded to the heater for
proper spark.
FIGURE 23 - Spark Pilot
-- Maintain a spark gap
of 7/64"
If the above conditions are normal and no spark occurs, replace the ignition controller.
If the main gas valve fails to open with a normal full size pilot ame established, check
for the following:
a) Voltage between black and brown leads on the main gas valve is 20 to 32 VAC
and there is no main gas ow with the built-in manual valve in FULL OPEN
position -- the main valve is defective.
b) No voltage between black and brown leads on the main gas valve -- check for
disconnected or shorted ame sensor lead or ame sensor probe.
When the above conditions are normal and the main gas ow is still off, the ignition
controller is probably defective.
NOTE: Model X furnaces manufactured prior to 10/2003 may be equipped with a
match-lit pilot.
To Next Page
Loading...
