I'm pretty sure the helmets aren't defective, they both worked well in normal welding situations, however they both overheated when I was doing continous high amperage work. Almost like they have a duty cycle that the manufacturer doesn't mention. None of the literature talks about a thermal shut down feature, so I have drawn the conclusion that the electronics get too hot and malfuction or simply shut off. I will be trying two other helmets, one just like mine, and one that is the same model from over a year ago, and seeing how they respond. I've never liked auto darkening helmets up until I tried the new generation of Optrels, now that the filter isn't just a green shade like the older ones, I found the true color ADF to be a lot better for my eyes. I'll see if the other lids do the same thing as the two I've tired, and determind the fault from there.