What is the Magnuson-Moss Warranty Act for Cars?

The Magnuson-Moss Act for cars places the burden on car dealers when warranty coverage claims are in question.


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You may enjoy the look or performance of a modified car. There's a common caution against modifications because they may void your car's warranty, but that's not 100% true. We'll explain.

What is the Magnuson-Moss Warranty Act for Cars?

The Magnuson-Moss Warranty Act is the federal statute colloquially known as the "lemon law," and it provides legally binding guidance on what a product's warranty covers. While not every product is required to have a warranty, all new cars leave the factory with coverage that typically lasts at least three years or 36,000 miles (whichever occurs first).

Cars are complicated devices with many potential (although rare) failure points, and their use can range from light-duty commuting to heavy-duty service as a taxi-cab or delivery vehicle. As a result, their warranties contain all sorts of provisions and lengthy disclaimers dictating what is and what is not covered by the warranty. Extended warranties, whether offered by an automaker, a dealer, or even a telemarketer, may have even more disclaimers that could make coverage increasingly difficult.

The good news is that the Magnuson-Moss Warranty Act instituted all the way back in 1975 by Congress means that a vehicle warranty must spell out its terms in clear language. This includes what types of parts an automaker might be compelled to repair or replace, as well as wear items (such as windshield wiper blades and tires) that are not typically covered under a warranty.

Can you Modify a Car without Voiding its Warranty?

The simple answer is: it depends. Modifying a vehicle can make it more difficult to maintain warranty coverage, though the Magnuson-Moss Warranty Act puts the burden on the automaker to prove that a modification directly contributed to the failure of a specific component. Acting as the automaker's agent, the franchised dealership will typically decide whether, say, oversize wheels and tires contributed to early failure of an axle. On occasion, the dealership may reach out to the automaker on your behalf to seek a resolution—though these situations are relatively rare.

What a dealership and an automaker cannot do, according to the Magnuson-Moss Warranty Act, is void a warranty simply because a modification is present. For instance, a lowered suspension with aftermarket springs and shocks is highly unlikely to directly contribute to an inoperative power door lock. In this case, the automaker should cover repair of the faulty door lock.

Aftermarket parts typically carry their own warranties, too. These warranties, while still falling under the guidelines set by Magnuson-Moss, are rarely as comprehensive as those that cover an entire vehicle.

Can you Modify a Financed Car?

Consumers looking to personalize their vehicles with everything from simple window tinting film to suspension lift kits may be concerned about how these modifications can affect the terms of their finance agreement and their warranty.

Typically, lienholders such as banks and automaker captive finance arms do not have any specific provisions that would prevent a vehicle owner from modifying a financed vehicle. This is not the case when it comes to a leased car, however, since terms will typically stipulate that the vehicle be in the same condition — aside from light wear and tear — when it is turned in at the end of the lease.

There are exceptions, of course. Some automakers offer factory-backed accessories that can usually be installed on a vehicle without voiding the terms of a financial agreement. Examples of this include wheels sold through the automaker's accessory catalog, as well as the suspension lifts that Jeep and Toyota offer for select models. Before you have these items installed, however, read the paperwork closely since it may stipulate that the accessories must be fitted by a factory-authorized outlet.

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Andrew Ganz
Andrew Ganz has had cars in his blood ever since he gnawed the paint off of a diecast model as a toddler. After growing up in Dallas, Texas, he earned a journalism degree, worked in public relations for two manufacturers, and served as an editor for a luxury-lifestyle print publication and several well-known automotive websites. In his free time, Andrew loves exploring the Rocky Mountains' best back roads—when he’s not browsing ads for his next car purchase.