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Issue 2 14/07/16
10 Appendix
10.7 Service procedure D24-III
Caution
Be Careful When Making Voltage Measurements or
Jumping Terminals Not to Damage or Deform Connectors
or Connector Pins.
Danger
120 volt exposure. To avoid personal injury, use caution
while performing this procedure.
10.7.1 Main burner operation testing
Condition:
Main burner will not light, Display
shows “Heating” under
temperature setpoint. Tank is cold.
Insert meter probes into back of
“Control” plug on control board to
contact pins for measuring voltage.
Is there 22-27 volts AC across pin
terminals 5 & 8? (Refer to wiring
diagram)
Disconnect brown wire lead from
“MV” terminal of gas valve.
Is there 22-27 volts AC across
brown wire lead & ground?
Be sure control display is showing
“Heating”,
pilot is lit
and control
is not sparking
. Recheck voltage
across control board
pin terminals 5 & 8 (MV & MV/PV)
Is voltage present?
Is pilot lit?
See “pilot will not light”
Check incoming gas pressure to
gas valve and manifold pressure to
burners (See next page for
procedure or checking manifold
pressure). If inlet gas pressure is
O.K., replace gas valve.
See “pilot lights, no flame signal”
Does control board continue to
spark with pilot lit?
Check wire harness for damage or
loose connections. Repair or
replace as needed.
No
Replace control board.
No
No
No
No
Yes
Yes
Yes
Yes
Yes
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