A window unit pulling around 10–12 A on a 12 AWG / 25 ft cord stays within rating with low voltage drop — adequate, provided the cord is rated for the run.
Stop and call a licensed electrician or emergency services now if there's smoke, sparks, a burning smell, heat, shock, or water near the problem. Otherwise it's safe to answer the questions below.
The likely readout
Most likely cause
12 AWG at 25 ft, ~12 A: 0.8% voltage drop — adequate
Ranked by fit to your answers
1
Adequate for this load and length
90
SAFE NEXT CHECK12 AWG carries 12 A at 25 ft with 0.8% drop — fine. Keep heat-producing appliances like space heaters on a wall outlet regardless.
Where to stop. Choosing or replacing an extension cord is homeowner-safe. Manufacturers and fire authorities advise plugging high-draw heating appliances such as space heaters directly into a wall receptacle rather than any extension cord. Anything involving the building's wiring or circuit rating is a licensed electrician's job. This is general information, not a quote and not a substitute for a licensed electrician.
Try the safe next check above. If it doesn't resolve it, or would mean working on wiring or a panel, stop and call a licensed electrician — don't replace parts on a guess. Open the full tool to change any answer for your exact situation, or try a related check below.
Electrical Fault Check provides general diagnostic information only. It is not professional advice, not a quote, and not a substitute for a licensed electrician. Do not work on live wiring. If you see smoke, sparks, burning smell, heat, shock, water exposure, or repeated tripping, stop using the circuit and contact a licensed electrician or emergency services as appropriate.