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8. Ignitor (Figure 6)
The nitride ignitor used on ML180UHA units is made from a
proprietary ceramic material. Ignitor longevity is enhanced
by controlling the voltage to the ignitor. To check ignitor,
measure its resistance and voltage. A value of 300 to 1300
ohms indicates a good ignitor. Voltage to the ignitor should
be 150VAC.
See figure 7 for resistance, and voltage check.
NOTE - The ML180UHA furnace contains electronic
components that are polarity sensitive. Make sure that
the furnace is wired correctly and is properly grounded.
FIGURE 7
Test 1 - Remove 5-pin plug
from control. Insert test pins
from meter into plug pin 1 and
5. If reading is correct test is
over. If reading is outside ac
ceptable range move to test 2.
Test 2 - Separate the 2-pin jack-
plug and again check resistance to
the ignitor. If reading is acceptable
then the problem is the wiring be
tween the jackplug and integrated
control. If reading is acceptable re
place the ignitor.
Voltmeter
(set to AC)
Test - Do not separate 5 pin
jack-plug. Use a true RMS me
ter and carefully insert test pins
in plug pins 1 and 5. Measure
voltage.
Voltmeter
(set to ohms)
Test 1
Test 2
