Ford B166a60 Jun 2026

: In some cases, the heater may work occasionally if there is a loose wire or a failing heating element. Potential Causes

When a door control unit flags a broken circuit, the problem generally stems from one of four vulnerable failure points:

Depending on where the open circuit is, you might experience issues with mirror adjustment or power-folding functions. Common Causes of "Heated Mirror Circuit Open"

When you activate the heated mirrors (usually by turning on the rear window defroster), the door module supplies power to a heating element on the back of the mirror glass. This element acts as a resistor, generating heat. The module monitors the electrical current flowing through this circuit. If the current is too low or non-existent, the module interprets it as an "open" circuit—a break that prevents the heater from working. It then logs the B166A-60 code. ford b166a60

: The side mirrors will fail to clear frost, ice, or fog when the rear defroster or dedicated mirror heat button is activated. Persistent Fault

To help narrow down your fix, could you share the of your Ford, and whether the issue is on the driver or passenger side ? I can provide the precise fuse layout or wiring diagram details for your vehicle. Share public link

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An open circuit implies that the flow of electricity has been blocked. In a Ford vehicle, this is usually caused by one of four specific issues: 1. Burned-Out Mirror Heating Elements

When your vehicle runs a self-diagnostic, the is responsible for monitoring the heated mirror circuit.

The driver or passenger door control module might fail to send power to the circuit. This element acts as a resistor, generating heat

After repairs, use a scanner like FORScan or a MaxiSys tool to clear the code and confirm the fix. When to Seek Professional Help

Installing non-heated replacement mirror glass or cheap aftermarket mirrors lacking the correct internal electrical resistance can trigger the door module to flag an open circuit fault.

Start with the cheapest potential fix: inspect the under-seat wiring and perform a zero-point calibration. If that fails, prepare to replace the passenger seat cushion assembly. And remember—always prioritize safety. If you are uncomfortable working around airbag systems, paying a professional $150 for a proper diagnosis is money well spent.

: The constant opening and closing of the driver or passenger door can fatigue the wires inside the rubber boot, eventually leading to a break.

: Could potentially refer to a specific engine or a series of engines. Ford has used various engine codes over the years (e.g., 5.0L V8 in the Mustang is often referred to as the "Coyote" engine, with its own set of codes and identifiers).