[DenverSteve]

I'm not suggesting your mechanic is incompetent or even wrong but; A) most mechanics don't worry or care about ignition switches and; B) these cars are driven everywhere COLD exists without issue. It's easy for a convertible car, driven topless a lot, to have grit, dust and debris in cracks, crevices and even ignition switches which can cause tight, squeaky or sticky issues that closed cockpit cars don't readily see.

Additionally, cold causes parts to shrink not expand which could make it loose or rattle before it "tightens" up. If it's problematic, you could take it out and clean it or replace it. I've never had a problem with one of mine but I have heard they can go out.