Bradford-White Corp D-38T-155 Service Procedure D24-III, Main Burner Operation Testing, 114

SERVICE PROCEDURE D24-III

Main Burner Operation Testing

DANGER

120 volt exposure. To avoid personal injury, use caution while performing this procedure.

CAUTION

Be Careful When Making Voltage

Measurements or Jumping Terminals

Not to Damage or Deform Connectors or

Connector Pins.

				Checking MV &
	Condition:			MV/PV control plug
				pins to gas valve
Main burner will not light,				for 24 volts output
Display shows “Heating” under temperature				during heating
	setpoint.			cycle (pilot must be
Tank is cold.				lit with no
				sparking).
	Is Pilot lit?		N	See “Pilot Will Not
				Light”
		Y

114

Does control board continue to spark with		Y	See “Pilot Lights, No Flame
pilot lit?			Signal”
	N

Insert meter probes into back of		Be sure control display is showing “Heating”,
“Control” plug on control board to contact
	N		pilot is lit and control is not sparking.				N
pins for measuring voltage.
			Recheck voltage across control board
Is there 22-27 volts AC across
				pin terminals 5 & 8 (MV & MV/PV)
pin terminals 5 & 8? (Refer to wiring
					Is voltage present?
diagram also see photo 14)
Y					Y
						Brown wire disconnected
						from “MV” terminal of gas
						valve

Replace control board.

Ground lug of

gas valve

				Check incoming gas pressure
				to gas valve and manifold
Disconnect brown wire lead from			Y	pressure to burners (See next
	“MV” terminal of gas valve.			p a g e f o r p r o c e d u r e f o r
Is there 22-27 volts AC across				checking manifold pressure). If
	brown wire lead & ground?			inlet gas pressure is O.K.,
	(see photo 15)			replace gas valve. (See photo
		N		on next page for gas valve
				inlet pressure tap)
Check wire harness for damage or loose
connections. Repair or replace as needed.

15

Checking main valve (MV) voltage to gas valve.

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