Bypass the Timer FM-DS3(e) on Hyundai heater
Here's the datasheet for the switch:
http://www.maxtronictech.com/MT-010x02.pdf

The easiest thing to do would be to get a slightly different FM DS(3) that has an on/off/timer switch, and set it to on. Problem solved, no wiring changes.

The second easiest thing would be to turn all the timer switches to the 'on' position.

The third easiest thing to do would be to bridge 3 and 4 with a jumper.  However, then there would be no way to turn this off -- not what you'd usually use for a heater!