there's a burning electrical smell coming from my legacy 920 motor unit. it still works though.

Diagnosis

The burning electrical smell emanating from your Overhead Door Legacy 920 is typically indicative of "thermal runaway" or a dielectric breakdown within the motor's start/run capacitor or the logic board's voltage regulator. Because the unit is still functioning, you are likely experiencing a partial failure where a component is overheating but hasn't yet reached the point of total circuit interruption. The smell is the result of PVC insulation or phenolic resin on the circuit board off-gassing as they reach critical temperatures. This most commonly occurs due to increased mechanical resistance. If the garage door tracks are misaligned or the springs have lost tension, the motor must draw significantly more amperage to move the door. This excess current generates heat in the motor windings and the capacitor. To confirm, unplug the unit and feel the motor housing; if it is hot to the touch even after 30 minutes of inactivity, the internal windings are likely compromised. If the smell is concentrated near the logic board (the green PCB), a capacitor is likely leaking or bulging, which creates a high-resistance path that generates intense heat.

How to Fix It

Stop using the opener immediately to prevent a permanent short circuit or a structure fire. Follow these steps to isolate and resolve the issue:

1. Power Down: Locate the circuit breaker for the garage and switch it off. Unplug the Legacy 920 from the 120V outlet to ensure no residual current is present on the logic board.
2. Mechanical Load Test: Pull the emergency release cord (the red handle) to disconnect the belt drive from the door. Manually lift the door. If the door feels heavy or doesn't stay open halfway, your springs are worn. This mechanical load is what caused the motor to overheat. Adjust the springs before powering the unit back on.
3. Inspect the Capacitor: Open the motor housing. Locate the start capacitor (the large cylindrical component). Look for "doming" at the top or oily residue leaking from the base. If the top is not perfectly flat, replace the capacitor with a matching microfarad (uF) rated part.
4. Clean the Logic Board: Use a can of compressed air to blow out any accumulated dust or spider webs from the PCB. Dust buildup acts as an insulator, trapping heat and causing components to burn.
5. Check Belt Tension: Ensure the drive belt is not overly tight, which puts unnecessary axial load on the motor shaft. There should be approximately 1/4 inch of play in the belt.

If That Didn't Work

• Replace the Logic Board: If you see charred "burn marks" or blackened areas on the green circuit board, the board has suffered a component failure. You will need to replace the entire control board assembly. Ensure you transfer your limit settings and remote codes to the new board.
• Motor Rewinding/Replacement: If the smell persists despite a new capacitor and a balanced door, the internal copper windings of the motor have likely suffered an insulation breakdown. Because the Legacy 920 motor is a sealed unit, it cannot be easily rewound; the entire motor assembly must be replaced.
• Verify Voltage Stability: Use a multimeter to check the voltage at the outlet. If your garage is receiving "brownout" conditions (voltage below 108V), the motor will draw higher amperage to compensate, leading to overheating. Install a surge protector or a voltage regulator if your local grid is unstable.
• Gear Nut Inspection: Check the drive gear for plastic shavings. If the internal nylon gear is stripping, it creates intermittent friction and "binding" that forces the motor to work harder, creating a burning smell from the motor's effort to overcome the jam.

Heads Up

• Fire Hazard: Never "test" a burning motor by running it repeatedly. A small electrical arc can quickly turn into a full-scale fire within the plastic housing.
• Spring Maintenance: Lubricate your door hinges and rollers every six months with a silicone-based spray. Reducing friction on the door is the best way to extend the life of the Legacy 920 motor.
• Capacitor Danger: Be extremely careful when handling the start capacitor; it can hold a lethal electrical charge even after the unit is unplugged. Discharge it using a resistor or a specialized tool before touching the terminals.
• Avoid Extension Cords: Never plug your opener into an extension cord or a power strip. The Legacy 920 requires a dedicated 120V circuit to prevent voltage drops that lead to motor overheating.