Bradford-White Corp M1TW60T*F, M4TW60T*F, M2TW50T*F, M4TW50T*F, M2TW65T*F Pressure Switch Testing

TTW SERVICE PROCEDURE III

Pressure Switch Testing and

Replacement

Pressure Switch Testing

Step 1. Position power switch on gas control to the “OFF” position.

WARNING

115 volt potential exposure. Use caution

making voltage checks to avoid personal injury.

Step 2. Remove the three screws (Phillips screw driver) from control access cover on blower assembly and remove cover (see photo 1).

Step 3. Carefully remove pressure switch from blower housing (see photo 2)

With steps 1,2 & 3

complete,

disconnect wire leads from

pressure switch.

Use a multi-meter set to the
ohms setting. With blower off,
check across pressure			N
switch terminals.
Are switch contacts open?
(no electrical continuity)
	Y
Position gas valve power					Y
switch to the “ON” position
and adjust thermostat				Check tubing and
to call for heat,		N		pressure tap on
this will start the blower.				switch for blockage.
Check with multi-meter, do				Is there blockage?
pressure switch contacts
close with blower running?
	Y
Switch contacts are OK.
See safety circuit trace
(page 29)

1

Pressure switch

wire leads

Check tubing and pressure tap on switch for blockage.

Is there blockage?

Y

Clear blockage

Y

Is vent

NN system

blocked

2

Pressure Switch

Slide pressure switch in direction of arrow while tilting slightly away from blower housing.

NReplace switch (see page 19)

Is vent system length				Y
			See blower testing
within vent table		Y
			(page 20)
specifications
			Is blower OK?
listed on pages 7 & 8
				N
	N
Reconfigure vent			Correct blower
system to be
compliant with			problem.
vent tables.

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