Bradford-White Corp M4TW40T*F, M4TW60T*F, M2TW50T*F, M4TW50T*F Safety Circuit Voltage Trace

TTW SERVICE PROCEDURE VIII

Safety Circuit Voltage Trace

Safety Circuit Voltage Trace

NOTE: This procedure assumes a cool tank.

WARNING

115 volt potential exposure. Use caution

making voltage checks to avoid personal injury.

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Remove three screws (Phillips Screw driver) from control access cover on blower and remove cover (see photo 26).

Position gas control switch to the “ON”
position and adjust thermostat dial to call
for heat, Is there 10 to 13 VAC between		Is LED on gas valve flashing
red wire leading to blower temperature N				Y
		the “heartbeat” code
switch and green ground wire?
		(alternating bright/dim)
Blower must be running during this
voltage check.			N
(see photo 27)
	Y	Verify 115VAC to gas
		control (see page 30)

No voltage from gas control,

call for technical support.

Is there 10 to 13 VAC between yellow			Is there continuity			Check for loose or
wire leading from pressure switch and N			through blower		Y	broken wire
green ground wire?			temperature switch?			connection at switch
(see photo 27)			(see page 22)			terminals
	Y			N
			Determine cause of blower
		Correct igniter/	temperature switch
		sensor problem.	activation and correct.

Do you hear or can you N see the igniter sparking?

Y

Safety circuit voltage is OK.

If burner does not light, observe LED flash code on gas valve and refer to troubleshooting section on page 13

Check igniter/sensor

Y Faulty cord set or

(see page 17)

gas control.

is igniter/sensor OK?

Green ground wire

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Red wire leading to blower temp. switch

Yellow wire leading from pressure switch

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