Diagnosis
The router requires a very specific, high-wattage power supply. Using a random adapter is extremely likely to cause damage because the voltage, current, and connector polarity must match exactly.
How to Fix It
You must obtain an exact-specification replacement. The ASUS RT-AX86U requires one of two official specs:
- +19V DC, 2.37A (approximately 45W)
- +19.5V DC, 2.31A (approximately 45W)
- Order the official replacement part (Adapter model: ADP-45AW B) from the ASUS Accessories Store or an authorized retailer.
- Contact ASUS Support directly with your router's serial number to purchase one.
- Purchase a high-quality 45W 19V laptop-style adapter from a reputable brand (e.g., Targus, StarTech) that exactly matches the voltage and has a current rating of at least 2.37A, ensuring the barrel plug size and polarity are correct.
If That Didn't Work
If a correctly-spec'd third-party adapter causes issues (router won't power on, boots intermittently), the adapter's quality may be poor or it may not sustain the required wattage under load. Revert to the official ASUS adapter. Also, double-check that the power connector is fully seated in the router's DC-IN port, as it can require a firm push.
Heads Up
Never use an adapter with a different voltage (like 12V or 20V), even if the plug fits. This can instantly fry the router's internal circuits. Avoid cheap, no-name adapters, as inconsistent power can lead to overheating, Wi-Fi dropouts, and premature hardware failure.