Diagnosis
The heating element isn't engaging. This could be due to a failed element, a problem with the thermal safety circuit, or the unit thinking it's already at the set temperature because of a faulty sensor.
How to Fix It
First, ensure you're using it correctly. 1) Set the thermostat dial (the outer ring) to a high temperature. 2) Make sure the function switch is set to one of the heat settings (I or II), not just the fan symbol. 3) Let it run for a few minutes—sometimes there's a brief delay. If you've done this and only get cold air, the heating element or a related internal component has likely failed.
If That Didn't Work
Try a full reset. Unplug the heater for 30 minutes, then plug it directly into a wall outlet and try again. This can sometimes clear a glitched internal safety lockout.
Heads Up
Don't continue to run it on a heat setting if it's only blowing cold air. The fan is trying to pull heat from an inactive element, which isn't harmful, but it means an internal part needs repair.