If you guys are going to go through with this, may I offer a suggestion?

Instead of contacting the vendor, document each incidents with the SD and follow up with Cusomter Relations every single time.

This will allow AC to build a document case on incident/maintenance reports, as well as repair and customer goodwill cost (Maintenance records and customer relations records of costs/compensation offered). AC will then have a solid case to present to their vendor in order to solve the issue.

Contacting the vendor directly will certainly create amazing lulz and memes, but in the end it may just complicate the situation further if it's actually taken seriously.

Just imagine if you think the fish in a restaurant is bad, and then you end up sending formal emails to Noref about the quality of their products.