"warranty void if opened" is also illegal in most consumer cases in the US, as common as it is for companies to apply this policy without being challenged on it

"warranty void if opened" is also illegal in most consumer cases in the US, as common as it is for companies to apply this policy without being challenged on it, and certainly in many other countries. Of course, they are certainly allowed to refuse to service warranty claims where a third-party part or repair caused the problem. Source: https://www.ftc.gov/news-events/blogs/business-blog/2018/04/ftc-staff-sends-warranty-warnings https://www.ftc.gov/news-events/blogs/business-blog/2018/04/... (blog post on the official FTC site - look at the third bullet point in their examples) Not mentioned in the above source, but the burden of proof that the third-party part or repair caused the problem is on the warrantor, not the consumer.