My steam mop will light up but want heat

Just guessing as there are several issues to address. Mineral buildup, a white powdery deposit from plain water use (not recommended) may choke off water flow to and inside the heating element rendering it unable to heat up water. distilled water is free of minerals that are deposited from heating when using plain tap water. If water isn't in the heating chamber, the heating element can burn out or a thermal fuse opens to prevent electrical and/or fire hazard. Once a thermal fuse blows, the heater is inoperative with thermal fuse replacement needed. The control board may be faulty. Advanced troubleshooting with familiarity using a multimeter, understanding how steam heaters operate with safety fuses, and ability to determine wiring layout are needed for diy repairs.