3 flashesBradford White · Ultra Low NOx D series gas · Water Heater

Bradford White Ultra Low NOx D series gas error code 3 flashes

Flue damper test circuit not working, damper not fully open

Needs attention soon

Also written as three flashes, 03

Quick answer

On Bradford White Ultra Low NOx D series gas, 3 flashes is a fault. It means flue damper test circuit not working, damper not fully open. A first thing to check: Damper not reaching its full open position.

Applies to: Bradford White Ultra Low NOx D series gas; Bradford White Ultra Low NOx residential D series gas codes · Water Heater
Type of code: Fault; Urgency: Needs attention soon
First safe check: Watch the damper through the draft hood while the burner runs and note how far it travels compared with a known good stroke.

Checked 2026-09-26

What 3 flashes means on this model

The damper responded but stopped short of fully open, so the burner is firing with a restricted draft path. The unit will not hold temperature and the burn is incomplete while it is in that state.

Symptoms you will notice

Three flashes, then a three second pause, repeating
Water takes much longer to recover than it should
Main burner sounds different, harder or more uneven
Unit cycles short instead of running a full cycle
Problem appears worse in cold weather when the metal contracts

Common causes

The code tells you what the control detected, not which part failed. These are the causes we see most often, roughly in order of likelihood:

Damper not reaching its full open position
Obstructed venting adding resistance
Failed or weak damper motor
Damper vane binding in its track
Corrosion on the damper linkage

What you can safely check

These are homeowner-level checks. None of them need you to open a live electrical compartment or work on gas.

Watch the damper through the draft hood while the burner runs and note how far it travels compared with a known good stroke.
With the burner off, check the vane for debris packed into the track.
Confirm the flue pipe is clear and that the total vent length and elbow count are inside the manual limits.
Listen for the damper motor running and stopping short, which points at the motor rather than the flue.

Do not do these

×Do not adjust the damper travel stops yourself to make the code go away. The stroke is set to match the draft the burner was certified against.
×Do not lubricate a damper that binds. Grit in the track gets worse and the motor can be damaged by the stall.
×Do not run the unit long-term on a partially open damper to get hot water, because the burn is incomplete while it is in that state.

When to call a technician

Book a technician, do not keep resetting it

This fault will not clear on its own. Every power cycle gives the control one more failed attempt, and repeated attempts are what turn a cheap part replacement into a seized or contaminated system.

This is a fuel-burning appliance, so treat anything involving a burner, gas valve or flue as technician work. If you smell gas at any point, leave the property and call the gas utility from outside rather than continuing to diagnose.
If the appliance has stopped mid-cycle, is making a noise you have not heard before, or smells burnt, stop reading here and call. Those are symptoms of something the fault code does not describe well enough.

Observing the damper stroke and checking for flue blockage is reasonable for a homeowner. Replacing the damper or its motor is a licensed technician job.

What it costs to fix

Parts

Flue damper assembly $90 to $260. Damper motor $60 to $150.

Labor

One to two hours for a damper or motor replacement, more if the flue needs correcting.

DIY or technician