Nothing (in the US) will "void" a warranty unless that thing causes the prob
It doesn't matter what you are adding- the law is clear.
A MFG can not deny warranty for any aftermarket part unless they can prove the aftermarket part caused the problem
If you do a stereo addition and your wiring breaks something- they don't have to warranty that (but everything else not impacted by your mod remains covered)
If you do a stereo addition and your wiring causes no harm you haven't impacted warranty coverage at all.
I mean that sounds great especially in a 1980's world where the only interactions between stereos and the rest of a car is plugging into the same dumb power source....
But that's not how things are any more. If your car refuses to go down for a software update because your new stereo's amp doesn't respond to the same command as Tesla's for going into sleep, or where you tapped power is now generating 12V battery faults that change how quickly your car goes to sleep, there's now a lot more interactions between your car and aftermarket accessories that could result in behaviors that you bring your car into Tesla service for.
And it does not take a lot of effort for Tesla engineering or service to come up with a semi-plausible explanation for how you caused the problem, which becomes difficult for you to refute. I've read many stories here where random Tesla malfunctions were explained to be caused by aftermarket modifications, whether it's dashcam installations or stereo systems from others (not Tsportline in particular, not trying to call anyone out).
As someone who's done aftermarket modifications to all 4 cars I've owned.... I have to say the truth is a little bit more of "it's a bit risky". You run the risk of being
hassled more. Kind of like when you use Comcast with your own modem as soon as you mention that fact they try to blame every problem on your modem. You might have to stomp your feet a little more or go to another service center, or be middleman between you and your installer...
I think a good example of the agreement I want is what some tuning company and Audi dealerships had. They sold ECU tunes through Audi dealerships and you sign a contract with them saying that if Audi ever refused a warranty claim, the third party would foot the bill. They went out of business though, I'm blanking on the name.... But that's kind of what you'd want to see to be useful to you. Compared to the number of times that dealerships / service centers try to blame 3rd party stuff, very rarely does a M-M Warranty Act end up going to court.... And financially I have my doubts on whether or not that's a victory.
Bottom Line: The M-M Warranty Act does not address whether or not manufacturers design devices that are unfriendly to aftermarket modification.
