Bradford-White Corp TTW ECO DEFENDER U4TW40T*FRN Manual De Usuario

 Page 42 

Note: This procedure assumes a cold tank. 

Step 1. 

Remove three screws (Phillips screw driver) from 

control access cover on blower and remove

cover.

115 volt potential exposure. Use caution making voltage checks to avoid 

personal injury.

Control access 

cover

Position gas control switch to the “ON” 

position and adjust the thermostat dial 

to call for heat. Is there 10 to 13VAC 

between the red wire leading to the 

blower temperature switch and the 

green ground wire? Blower must be 

running during this voltage check (see 

photo 15). 

Is LED on gas valve flash-

ing the “heartbeat” code 

(alternating bright/dim)? 

No voltage from gas control. 

Call for technical support. 

Verify 115VAC to gas con-

trol (see page 41). 

Is there 10 to 13VAC between 

the yellow wire leading from the

pressure switch and the green 

ground wire (see photo 27)? 

Is there continuity through 

the blower temperature 

switch (see page 31)? 

Check for loose or broken 

wire connection at switch 

terminals.

Do you hear or can you 

see the igniter sparking? 

Check igniter/sensor (see page 

22). Is igniter/sensor OK? 

Correct igniter/

sensor problem 

Determine cause of blower 

temperature switch activa-

tion and correct.  

Faulty cord set 

or gas control

Safety circuit

voltage is OK.  

If burner does not light, ob-

serve LED flash code on gas 

control and refer to trouble-

shooting section on page 17. 

Green ground wire 

Red sire leading to 

blower temp. switch 

Yellow wire leading

from pressure switch 

N

N

Y

Y

N

Y

N

Y

N Y 

Y

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