mpopeskov, basically it's whether or not it's getting the right current. Just like any other electronic thing. If it's not, which with part of it not working right it shouldn't) then the "fix" is to replace the unit. They don't open it up. Most probably don't bother since they've come in under the warranty time period & it's quicker to just replace it.
The ones they take out get sent to the testing lab, where ALL the "bad" parts get sent when under warranty. It will get tested, & possible actually fixed, then sent back to the parts place as a remanufactured one.
