Bryant 355MAV Error Code 15: Blower Motor Lockout
What Does Code 15 Mean?
Status code 15 on the Bryant 355MAV is a blower motor lockout. The control detected that the blower failed to reach 250 RPM or failed to communicate within 30 seconds of being turned on, and this happened in two successive heating cycles. After the second failure the board locks out, then auto-resets after 3 hours.
The 355MAV uses a variable-speed ECM blower that talks to the control board digitally rather than just switching on. When the motor cannot spin up to speed or the communication link drops, the board cannot confirm air is being moved. Without proven blower operation the furnace will not run, because heat would build in the heat exchanger with nothing to distribute it.
This lockout is the escalated form of code 41 (Blower Motor Fault), which is the single-cycle version of the same failure. The most common cause is a failed ECM motor or its integrated control module, which can fail independently of the windings. A wiring or connector fault between the board and the motor is the next most likely cause. Diagnosis needs specialized testing and replacement is a technician job.
What You'll Notice
- The blower does not run during a call for heat, so little or no warm air reaches the vents
- The furnace may start to heat then shut down when the blower is not confirmed
- The motor may hum, buzz, or make an unusual noise while trying to start, then stop
- The status LED flashes code 15 (one short flash, five long flashes)
- The furnace goes dead for up to about 3 hours, then retries and may lock out again
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Failed ECM blower motor | Most common | ✗ Call a pro → |
| Wiring issue between control board and blower motor | Common | ✗ Call a pro → |
How This Is Diagnosed
A technician confirms the motor is receiving both its high-voltage supply and its low-voltage control signal, then checks the digital communication between the board and the ECM module — a dropped link produces this code even when the motor is otherwise sound. Connectors and the wiring harness are inspected for loose or corroded pins.
If power and signal are present but the motor still will not reach speed, the ECM motor or its integrated module is tested and typically replaced. Because this involves the variable-speed motor and its control circuitry, it is not a homeowner repair.
When to Call a Professional
This code involves components that are not homeowner-serviceable, so have a licensed HVAC technician diagnose and repair it. Keep in mind:
- The blower does not run during heating cycles and the furnace shows code 15
- The motor hums or buzzes but does not spin up
- The furnace repeatedly locks out after the 3-hour reset
- The lockout follows repeated code 41 blower motor faults
Frequently Asked Questions
What is the difference between code 15 and code 41 on a Bryant 355MAV?
Code 41 is the single-cycle blower motor fault. When it happens in two successive heating cycles, the board escalates to code 15, a lockout. Both point to the ECM blower motor failing to reach speed or communicate.
Can I reset a code 15 lockout?
The board auto-resets after about 3 hours, or you can cut power for 30 seconds to reset sooner — but if the motor or wiring problem remains, it will simply lock out again. The underlying fault needs a technician.
Is an ECM blower motor expensive to replace?
ECM motors cost more than older PSC motors, and total price depends on the specific motor and local labor rates, so it varies by region. A technician can confirm whether it is the motor, its module, or wiring before quoting.
Sources
✓ Verified against manufacturer service manual — March 2026