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My friend had the same problem with his sc400. Says it's usually a relay located not too far away from your left foot when your driving. Sry about not being too specific but it should be a good place to start..

I had this happen in my SC300. Check your fuses including A/C AND cigarette lighter fuse.

2011-08-29 19:05:56
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Q: What could be the problem in a Lexus sc400 when a heater ac unit lights up but none of the buttons work and nothing displays on the screen?
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