What Actually Voids Your Warranty?

You will be familiar with the tactics that many companies use to get out of honoring a warranty.

The sticker over the screw that reads “warranty void if removed”. The clause in the manual that warns “any modification voids the warranty”. The FAQ page that says “all repairs must be done by an authorized dealer”.

If you own a car or a lawn mower or anything with a circuit board, you’ve seen these warnings. I work on my own cars and motorcycles. For years I worried a claim would be denied because I changed my own oil or fitted an aftermarket part. That worry only ended when my Toyota’s warranty ran out in August.

So this week I looked into where the law actually stands. It turns out I never needed to worry. Most of those warnings claim more than the law allows. They stay in place because many consumers have their claim denied and stop there. You should know that you have recourse beyond that.

Today’s article outlines what the law says, what 111 current warranty policies say, and what to do if your claim is denied for the wrong reason.

The Magnuson-Moss Warranty Act is a US Federal law passed in 1975. It bans any manufacturer from making its warranty depend on you using a particular brand for parts or a particular company for service.

The only exception is if the manufacturer provides those parts or that service for free. A company can also ask the FTC for a waiver. In 51 years, three have applied, and all three were refused.

The FTC’s rule on the Act has been on the books since 1977 and gives an example of the language it forbids:

"This warranty is void if service is performed by anyone other than an authorized 'ABC' dealer and all replacement parts must be genuine 'ABC' parts."

The rule is also clear about what warranty exclusions are permitted to manufacturers. They may deny claims for "defects or damage caused by 'unauthorized' articles or service." They may deny a claim "where the warrantor can demonstrate that the defect or damage was so caused."

So the obvious question is: whose responsibility is it to prove whether the damage was caused by my shoddy repair work, or their shoddy design?

The FTC is clear: "Before they can deny warranty coverage, the manufacturer or dealer must first prove the aftermarket or recycled part caused the needed repairs."

The law places the burden of proof on manufacturers, regardless of any exemption clauses they may include in their policy.

Before getting onto how to handle a denied warranty claim, we should cover an important distinction. The warranty warnings you see on stickers and in manuals lump three different acts together. The law separates them clearly.

1. Repair - Fixing it yourself, or paying a shop the manufacturer didn't bless.

Protected. This is the first half of the FTC’s example policy above: "void if service is performed by anyone other than an authorized dealer." The bare fact of an outside repair cannot legally end your coverage.

2. Replace - Fitting another company's part.

Protected. This is the second half: "all replacement parts must be genuine 'ABC' parts." They can only deny if they can prove that the part caused the failure.

3. Modify - Changing the thing from how it was sold.

The Magnuson-Moss Act never mentions modification, so this is the least settled of the three. The one time the FTC has drawn the line was in its 2022 order against Harley-Davidson. The agency barred Harley from saying a warranty "will or may be void" because of an unauthorized modification, but allowed Harley to exclude damage caused by one.

The FTC ordered that Harley’s policies be rewritten. The 2026 Softail warranty now reads:

"Taking your motorcycle to be serviced by a repair shop that is not an authorized Harley-Davidson dealer will not void this warranty, and using non-genuine Harley-Davidson parts alone will not void this warranty."

That is repair and replacement, in the FTC's mandated words. A few paragraphs later the warranty applies the causation test to parts, excluding damage from any part, "even those installed by an authorized Harley-Davidson dealership, that cause a genuine Harley-Davidson part to fail."

The order did allow Harley one exclusion with no causation test. A bike tuned with software lacking a California Air Resources Board order or EPA approval loses every powertrain claim "if Harley-Davidson or any authorized Harley-Davidson dealer has any information showing" it.

On repair and parts you have rights. On a modification you have the manufacturer's terms, so if you do tune a vehicle under warranty, read those terms first.

A warranty’s legal text and the warnings written around it are not the same thing. The legal text is written by lawyers and is the true legal basis of the policy. The warning stickers, FAQ pages and customer support lines have no real legal basis, yet these are what most consumers go by.

Samsung's appliance warranty, for example, excludes only damage caused by outside service. Its appliance FAQ page, on the other hand, lists "unauthorized repairs or parts not supplied by Samsung" under what is not covered.

So I looked into the current US warranties of 107 brands across 13 categories, from cars to blenders, to see what each one says about outside repair and non-branded parts and whether their policies align with the FTC’s rules.

That came to 111 documents, because a few companies publish separate warranties for different product lines. Every document, the clause it uses, and a link to check it are in the appendix. They fall into five groups:

Of the eleven that say the warranty is void if anyone but the company or its dealer repairs the product, Vitamix sells a "10 Year Full Warranty." "Full" is a federal label, and a full warranty can't ask the owner to do anything beyond reporting the defect. Inside it states that the warranty "is also void if repairs ... are performed by someone other than either Vitamix or an authorized Vitamix Service Provider." Bose: "Unauthorized repair, modification or customization of your product voids this warranty." Sena: coverage is "terminated prematurely" if "an unauthorized person has tried to disassemble, repair, or modify the product." Just an attempt at a repair yourself is enough to void.

So 43 of 111 make coverage depend on outside repair or parts, or on any modification, without a causation test.

Only 9 tell the owner their actual, federally protected rights.

Whether that is carelessness or strategy, the effect is the same. The clauses work on every owner who reads them as binding and stops there. I’m certain that describes most people. The next section explains why companies are able to print those clauses, with little consequence.

By category, cars, motorcycles and major appliances are the cleanest: only 1 of 6 car warranties, 1 of 8 motorcycle warranties and 3 of 15 appliance warranties suggest that outside repair or aftermarket parts would void warranty. Home batteries and EV chargers (3 of 4), grills and kitchen gear (5 of 7), bicycles (5 of 7), and mowers and generators (7 of 11) are the worst. Bear in mind, the sample size is not very large, so conclusions on sector performance should be taken with a grain of salt. The full breakdown is in the appendix.

Another interesting data-point: in 2021 PIRG called and asked 43 appliance makers whether independent repair voids the warranty. All 43 said yes. Nobody has re-run the calls since. Perhaps that would be a worthwhile thing for us to do.

The Act gives the FTC no power to fine for a first violation. A fine can only be issued for breaching an order once one exists. The FTC admitted in 2021 that "current law does not provide for civil penalties or redress."

In 51 years the legislation has only produced two batches of warning letters, in 2018 and 2024, and three consent orders in 2022 with no fine.

The FTC hasn't sent a warranty warning letter or brought a warranty case since July 2024.

Owners don't sue over the clauses alone either. A sentence in a warranty does no harm until a claim is denied, and a denied claim on a blender or a mower is rarely worth a lawyer's time. On top of that, many warranties carry an arbitration clause that blocks a class action.

So given that there is no pushback from the government, plaintiff lawyers, or consumers themselves, companies will keep pushing those exclusion clauses.

Having said that, consumers have more power than many realize. What the law offers is clear recourse when a claim is denied. Under the Act consumers can sue for the cost of the repair, in small claims court or in arbitration. Once a legal dispute is initiated, manufacturers must prove that your part or outside repair caused the failure. If you hire a lawyer and win, the court can order the company to pay your fees. That is the only viable enforcement mechanism I see.

Ignore the sticker. To repair or even inspect most things you have to open the case, yet the sticker says opening voids the warranty. It doesn't. The FTC's business guide explicitly lists a seal that voids coverage when broken as prohibited. A seal can lawfully be placed on a product and it does show that it was opened. They can raise that when arguing over what caused the failure. On its own it is not a reason to deny.

Keep the invoice. When a claim is denied after outside work, the argument is about cause. They will say the shop or the part must have caused the damage. Without records you can't answer that, and the denial may stand. With an invoice that names the part, the work and the date, you can show what was touched and when. Keep every receipt for the life of the warranty. If you do the work yourself, keep your own detailed records and keep all receipts for any parts/fluids you purchase.

Write the letter. When a claim is denied over outside repair or parts, write to the seller and then the manufacturer. Send it certified mail with a return receipt, so there's proof it arrived. The letter also clears a legal hurdle. Before you can sue under the Act, the company must be given “a reasonable opportunity to cure.” This letter is that opportunity. Quote their stated reason back. Cite 15 U.S.C. 2302(c) and 16 CFR 700.10(c). Ask them to name the defect they say your part caused, and the evidence for it. Give a date. Say what you want as restitution.

Most denials come from a customer-service tier that is applying a standard operating procedure from corporate. A warranty denial is your cue to ask for proof. A written request for proof, with the citations, is what you need to formally invoke the law. Before you do that, you are just accepting the company’s defensive, cost-saving procedure.

Here is a template you can use (you may need to adjust slightly for your specific case):

Kia denied a Pennsylvania couple’s engine claim last winter because their oil-change receipts lacked a VIN. Jamie and Debbie Rekasie had fourteen documented oil changes on a 2019 Optima that failed at 80,000 miles, inside Kia’s 100,000-mile powertrain warranty. Kia approved the replacement only after a Pittsburgh television station called. Michael Brooks of the Center for Auto Safety described the pattern:

"Often, the first tactic is to deny the claim and hope the consumer goes away."

Now you know how not to go away.

For illustration, here is an invented case, though I’ve applied real numbers:

The car is at 45,000 miles, inside its 5-year, 60,000-mile powertrain warranty. Oil changes were all done at an independent shop. An aftermarket cold-air intake was fitted. The transmission fails, and the service writer denies the claim "due to the aftermarket parts on the vehicle," an argument a GM dealer has used in real life. A replacement transmission runs $6,238 to $6,764. Call it $6,500. The law asks them to show precisely how an aftermarket intake or an oil change caused this particular transmission to fail. That burden is theirs from the start. In practice, nobody makes them honor it until you dispute the denial, in writing or in court.

To begin proceedings, your outlay is $10 to send the letter and $55 to file in Colorado small claims or $75 in California, if it comes to that. Depending on the state, you’re looking at a range of $30-$379 to file.

Granted, many of these warranties carry an arbitration clause. Arbitration sends disputes to a private arbitrator instead of a judge, and a class-action waiver says you must make your claim individually. But the consumer's fee in arbitration is capped at $225 and the company pays the rest, which can run to thousands before its lawyer bills an hour.

If you'd rather hire a lawyer, a court can make the company pay a winning owner's legal fees by the hour. In Waldock, an Alaska owner won $17,686 and the court awarded $36,526 in fees on top.

So you have $90 at risk on a $6,500 claim. Their cheapest move, once a letter citing the law and a request for proof arrives, is often to just fix the transmission.

If a company has denied a warranty claim of yours because you used an outside shop or fitted another company's part, reply to this email with the product and what they told you. Tell me whether you'd be willing to send the letter and, if it comes to it, file in small claims. It would be interesting to follow one or two of these from letter to outcome and report back.

Thank you, as always, for your readership and support.

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