Goodman furnace code b6: Motor Over/Under Voltage or Over-Temperature Trip
Professional repair
What does b6 mean on a Goodman furnace? The ECM blower motor shut itself down because line voltage was too high (over 140 VAC) or too low (under 70 VAC), or because its power module overheated. The motor restarts once the condition clears, but the furnace can't run while the motor is off. For overheating, the manual names high ambient temperature or heavy motor loading as the likely cause.
Before you touch anything: the six signs that mean stop troubleshooting and call a pro →
Check that the supply voltage is within the range on the rating plate, and check motor loading.
What causes it (in order of likelihood)
- Line voltage above 140 VAC or below 70 VAC TECH
- Power module overheating from high ambient temperature or heavy motor loading TECH
Parts for this code
No specific part number is verified for this code — it typically points at wiring, power, a blown fuse, or communication between components rather than one standard replacement part. If your diagnosis does land on a replaceable component, match its part number against your model's parts list before ordering.
Questions about this code
What does b6 mean on a Goodman furnace?
The ECM blower motor shut itself down because line voltage was too high (over 140 VAC) or too low (under 70 VAC), or because its power module overheated. The motor restarts once the condition clears, but the furnace can't run while the motor is off. For overheating, the manual names high ambient temperature or heavy motor loading as the likely cause.
How do I fix Goodman furnace code b6?
Measuring voltage is technician work. One of the checks is whether the furnace's supply voltage falls within the range on its rating plate.
How much does it cost to fix Goodman furnace code b6?
Cost depends on whether the cause is the home's supply voltage or the motor overheating under load. Those are different jobs, and a supply problem may need an electrician.
Applies to
GMVC96 · GCVC96
Different Goodman generations use different code maps. If your series isn't listed, don't assume this meaning — check your blower-door label.
Same control platform, same code: Amana furnace code b6
Full code lists for the other brands on this control platform: Amana furnace codes
Verified against Goodman GMVC96/GCVC96 Service Manual, p.45 — “This condition occurs if the line voltage is too low or too high”
Verified against Goodman GMVC96/GCVC96 Service Manual, p.51-52 — “b6 OVER/UNDER VOLTAGE TRIP OR OVER TEMPERATURE TRIP”
Verified against Goodman Diagnostic Code Identification System (GMVC96, GCVC96, AMVC96, ACVC96; code b6) — “Blower Motor Over/Under Voltage Trip or Over Temperature Trip”
Last verified 2026-10-19 · page updated 2026-10-20 · how we verify
Related Goodman furnace codes
These codes use the same dual 7-segment display (two-stage variable-speed) system.