17
DES3
Series
Check that gas pressure is within
minimum and maximum inputs
as indicated on the heater’s rating
plate. Is gas pressure ok?
No
Differential switch may be faulty or there is a
restriction in the exhaust or intake.
Correct problem.
Yes
Check for damaged insulation
or loose terminals on the
high voltage spark wire.
Is it ok?
Yes
Electrode sensing may be
faulty or flame signal may
be weak. Check that heater
is operating at proper gas
pressure as indicated on
the rating label. Clean or
replace electrode if needed.
No
Check the gap
on the igniter. Is the
gap between 1/8 in.
and 3/16 in.?
Adjust gap.
No
4.0
Troubleshooting Guide
Flame Current Check: Single Spark & Sense
To measure flame current, disconnect input voltage, then insert a 0-50 μA DC meter and capacitor in series with the
spark electrode as shown below. Reconnect input voltage and initiate call for heat. After sparking is complete and
flame is established, meter should read 1.0 μA or higher while flame is established. If meter reads below “0” on the
scale, meter leads are reversed. Disconnect power and reconnect meter lead for proper polarity.
Replace.
Check the spark
electrode. Is the
ceramic cracked
or loose?
No
Yes
Replace electrode.
