have somebody tried to do webasto control unit? i have an old webasto hl 18 air heater and control unit is broken. i just thinking it's really simple how it's works.. first fuel pump start to pump and i think glow plug starts to heat same time, 5 seconds later heater fan starts to blow air and webasto is burning fuel. that's it. of course there is flame detector and what was that another.. some kind of temperature sensor..? maybe temperature sensor is not necessary. when you stop heating glow plug stops to glow and fuel pump stop, heater blow about 5min and stop too. so in circuit i need delay for heater fan for start and stop, one delay for fuel pump and some kind of circuit for flame watch. everything i would put working with external relays so it doesn't have to stand so much electricity. thank you so much! sorry my english is not so good.