Bradford White Defender Pilot Won't Stay Lit

The Short Answer: If a Defender pilot goes out when you release the knob, the gas control isn’t getting enough signal from its flame sensor (a thermocouple or thermopile, depending on the control), the flame isn’t covering the sensor, or the resettable thermal switch has opened. If it holds but goes out hours or days later, look at combustion air, a lint-clogged flame arrestor, venting or gas supply.

First, which gas control do you have?

Bradford White has fitted Defender (FVIR) tanks with several gas controls, and the right part depends on which one yours has. Bradford White’s Defender service manual covers four:

• White Rodgers mechanical (no status light): uses a thermocouple.
• White Rodgers electronic, Honeywell V1 and Honeywell V2 (green or colored status LED): use a thermopile, which generates far more voltage than a thermocouple.

Check whether the control has a status light, and photograph the label on it. That tells the technician which parts and procedures apply.

Two different failure patterns

It goes out as soon as you release the knob. Bradford White’s troubleshooting chart lists these causes:

• a poor sensor connection at the gas control, or a sensor not fully seated in the pilot bracket
• a pilot flame that doesn’t fully cover the sensor tip
• a weak sensor
• an open high-limit (ECO) or a faulty magnet inside the gas control
• an open resettable thermal switch on the inner combustion door

It lights and runs, but the pilot goes out periodically. The chart points to insufficient combustion air, clogged jacket openings or flame arrestor, a venting problem, or inconsistent gas pressure. Bradford White notes that the Defender’s thermal switch shuts the burner and pilot down if lint, dust or oil restricts the airflow through the arrestor plate.

What you can do

1. Relight once, exactly as the label says. If your control has a status LED and it’s lit solid after you turned the knob to OFF, wait until it goes out before you relight. Bradford White says the control is in shutdown mode until then.
2. Hold the knob for the full time on the label before you release it.
3. Look at the area around the heater. Lint from a nearby dryer, pet hair, dust and stored items can block the air openings around the base of the jacket. Keep the area clear. Store gasoline, paint and solvents in another room. The Defender system is designed to shut down if it detects flammable vapors.
4. Note when it goes out. Did it happen when a dryer, range hood or bath fan was running, or on windy days? That helps the technician separate an air supply or draft problem from a failing part.

If the pilot won’t hold after one careful attempt, leave the heater off and call for service. Repeated attempts won’t fix a weak sensor or a tripped safety switch.

What the technician will check

• Sensor output with the pilot lit: thermocouple or thermopile millivolts, measured against Bradford White’s limits for your control.
• The pilot flame pattern, pilot orifice and pilot tube, and whether the flame fully covers the sensor.
• The resettable thermal switch on the inner door. If it has opened, the technician finds out why before resetting it, because it opens on flammable vapors or a restricted air supply.
• The ScreenLok flame arrestor and jacket openings, which are cleaned during service.
• Gas pressure, venting and the condition of the inner door gasket. The gasket seals the combustion chamber and must be refitted correctly.

Pilot assemblies, thermocouples and thermopiles are routine parts. If the magnet or ECO inside the gas control has failed, the control is replaced. If the tank is leaking into the combustion chamber, the heater needs replacing.

Frequently Asked Questions

Q: Should I buy a thermocouple? A: Only if your heater has the mechanical White Rodgers control with no status light. Controls with a status LED use a thermopile, and a thermocouple won’t work on them. Let the technician confirm the part.

Q: Where is the reset button on a Defender? A: The resettable thermal switch is on the inner door of the combustion chamber. Bradford White’s service manual tells technicians to find the cause before pressing it. A tripped switch means the burner overheated or couldn’t get enough air.

Q: The status light flashes twice after the pilot lights. Is that related? A: Yes. Two flashes means the thermopile signal is weak. See Bradford White weak pilot signal. If the pilot won’t light at all, see Bradford White pilot won’t light.