so hey, brand new here. i have an old D610 24". has been my work horse for decades. Well, i called airmark and chatted with them. they can't help. So, I'm not exactly sure where the issue is, but when i move the arm to lower the wheels the head does not move to do it's initial measurement. I see the little blue switch connected to it that plugs into the motherboard. If material is not being fed and i lower the arm the fan turns on and it does with material being fed though for initial loading of vinyl. Problem is, when i try ad load material ... it looks like the front sensor is sensing vinyl but the back sensor does nothing. i can put my finger over sensor at the front of machine and the fan turns on to suck material flat, i try this with the rear sensor and nothing. I don't know if my problem is with the switch inside the side cover connected to the lowering arm for the wheels or if it is the rear sensor. but either way i want to keep using my summa. i may need to buy one if someone has one they's sell I'll probably use for parts. My most recent repair was pinch roller wheels from airmark for 50 bucks per wheel. Anyway, glad to be here.