Bryant 355MAV Error Code Continuous OFF: No Power
What Does Code Continuous OFF Mean?
On the Bryant 355MAV, the control status indicator LED is the board's heartbeat. A continuous-OFF LED means the Variable Speed Furnace Control board is receiving no power at all. Because this board governs everything on this furnace — the two-stage gas valve, the variable-speed ECM blower, the inducer, and every safety switch — nothing will run until the board is powered again.
Bryant lists the diagnostic check for this state as verifying line voltage at L1 and L2 and 24 VAC at SEC-1 and SEC-2. In plain terms, either the 115 VAC feeding the furnace is gone, or the transformer that steps it down to the 24 VAC the board needs has failed. The most common real-world cause is simply a tripped breaker or a furnace power switch that got flipped off.
Do not confuse this with code 24 (Secondary Voltage Fuse Is Open), where the board still has line power but its 24 VAC fuse has blown from a wiring short, or with a steady-ON LED (normal standby). A completely dark LED points to a loss of incoming power rather than an internal fault the board could report.
What You'll Notice
- The status LED on the control board is completely dark, with no flashing at all
- The furnace does nothing when the thermostat calls for heat — no inducer, no ignition, no blower
- The furnace is silent even when you turn the thermostat well above room temperature
- If the breaker tripped, other devices on the same circuit may also be dead
- A thermostat powered from the furnace (common wire) may go blank
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Tripped circuit breaker or blown fuse | Most common | ✓ DIY fix → |
| Furnace power switch turned off | Common | ✓ DIY fix → |
| Faulty transformer or wiring | Uncommon | ✗ Call a pro → |
How This Is Diagnosed
The cause is isolated from the outside in. First the incoming 115 VAC supply is confirmed by checking whether the furnace breaker has tripped and whether the service switch on or near the furnace is on. Next the blower-door interlock switch is checked, since an open or misaligned door can cut power to the board.
Only if line power is confirmed present does attention move to the transformer and low-voltage side — verifying 24 VAC at SEC-1 and SEC-2. A missing 24 VAC reading with good line voltage points to a failed transformer or a break in the wiring, which is where the job crosses into work for a technician.
How to Fix It: Check the Circuit Breaker, Power Switch, and Door
What You'll Need
Steps
- Shut off the furnace power switch and the gas supply before you start Turn the service switch on or near the furnace to OFF and turn the gas shutoff valve to the OFF position (perpendicular to the pipe) as a precaution before inspecting anything. If you smell gas at any point, leave immediately and call your gas company.
- Reset the circuit breaker Go to your home's electrical panel and find the breaker for the furnace or HVAC system. If it sits in the middle (tripped) position, flip it fully to OFF and then back to ON. If your panel uses fuses, check the furnace fuse and replace a blown one with the same amperage.
- Confirm the furnace power switch is ON Look for a standard-looking light switch on the side of the furnace or on a nearby wall. It is easily mistaken for a room light switch and turned off by accident. Set it back to ON.
- Make sure the blower access door is fully seated The 355MAV has a door interlock switch that cuts power when the blower door is off or loose. Reseat the door firmly so the interlock is pressed in.
- Restore gas and verify the LED Turn the gas supply valve back to ON (parallel to the pipe) and confirm power is restored. Through the sight glass or access opening, the LED should now be lit. Set the thermostat to call for heat and confirm the furnace starts.
When to Call a Professional
Contact a licensed HVAC technician if:
- The breaker trips again immediately after you reset it
- The power switch is on and the breaker is not tripped, but the LED stays dark
- The LED is off even with the blower door firmly seated
- There is a burning smell or visible scorching near the furnace or transformer
- You are not comfortable working at your electrical panel
Frequently Asked Questions
Why is the light on my Bryant 355MAV control board completely off?
A continuous-OFF LED means the board has no power. The usual causes are a tripped breaker, a furnace power switch turned off, or an open blower-door interlock. If those are all fine, a failed transformer or broken wiring is likely and needs a technician.
Is it safe to leave a furnace with no power over the winter?
The furnace itself is not producing heat or burning gas in this state, so it is not an immediate hazard, but an unheated home risks frozen pipes. Restore power promptly, and if the cause is a repeatedly tripping breaker, have it diagnosed rather than repeatedly reset.
How much does it cost to replace the transformer on a 355MAV?
A transformer is a relatively inexpensive part, but total cost depends heavily on local labor rates and whether the short that damaged it must also be repaired, so prices vary widely by region. Get a written estimate before authorizing work.
Sources
✓ Verified against manufacturer service manual — March 2026