Carrier 58MVC Error Code Rapid Flashing: Reversed Line Voltage Polarity
What Does Code Rapid Flashing Mean?
A rapidly flashing amber LED on the Carrier 58MVC indicates that the 115 VAC line voltage polarity is reversed. The furnace's control board requires the hot and neutral wires to be connected to the correct terminals for the flame sensing circuit to function properly. With reversed polarity, the flame sensor cannot reliably detect the presence of a burner flame.
This condition typically occurs after the furnace has been installed, after a control board replacement, or after electrical work in the home. The hot (black) wire and neutral (white) wire may be swapped at the furnace disconnect, the junction box, or the outlet supplying the furnace. It can also happen if the home's wiring at the breaker panel was connected incorrectly.
The furnace will not operate safely with reversed polarity. Even if it occasionally starts, the flame sensing safety circuit is compromised, which could allow the gas valve to remain open without confirmed combustion. An electrician or HVAC technician must identify where the polarity is reversed and correct it with the power turned off at the circuit breaker.
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Hot and neutral wires reversed at furnace connection | Most common | ✗ Call a pro → |
When to Call a Professional
Contact a licensed HVAC technician if:
- The LED is rapidly flashing — an electrician or HVAC technician must correct the reversed line voltage polarity
- This code appeared after installation, service, or electrical work
✓ Verified against manufacturer service manual — March 2026