The Risk You Take On With a Customer-Supplied Part

Why this matters

Most shops argue about customer-supplied parts as if the question were the lost parts margin. That is the smallest thing at stake. What actually moves is the warranty position: the part maker's remedy runs to whoever bought it, the labor to take the failed one out and put another one in belongs to nobody by default, and the customer's mental model is that the company who installed it owns the outcome. You end up the last party standing in front of a failure you did not cause and cannot recover from anyone. The good news is that this is a priceable risk, and the number that prices it is expected re-do labor hours, not the price of the part.

What actually transfers when the customer buys it

• The remedy follows the purchaser. A part warranty is between the seller or maker and whoever bought it. When it fails, the customer holds the claim and the claim is almost always for a replacement part, not for the labor to install it. They will need the proof of purchase, which they may or may not still have.
• The labor is orphaned. Nobody's part warranty covers your time to remove and reinstall. If you do not say who carries it, you have carried it, because you are the one holding the tools when the failure gets reported.
• The diagnosis becomes contested. When a shop-supplied part fails, the question is whether the part was bad. When a customer-supplied part fails, there is a second candidate: whether the diagnosis was right in the first place. You now have to prove the part failed rather than that you misread the fault, and you are proving it about a component you did not select.
• Provenance goes dark. You do not know where it sat, for how long, at what temperature, or whether it has already been installed once and returned. Elastomeric seals, electrolytic components, and anything with a stored charge or a cure date all age on a shelf.

The warranty position, stated plainly

Here is the part that surprises owners. The equipment maker's written warranty on a consumer product generally may not be conditioned on the customer using branded parts or authorized service unless the article is supplied free of charge or the Federal Trade Commission has granted a waiver. That is the Magnuson-Moss Warranty Act, 15 U.S.C. ch. 50, a federal statute enforced by the FTC, and it binds the warrantor of the product, not you. A failure that the substituted part actually caused can still be excluded from that warranty, and proving causation is the customer's problem in that fight, not yours.

So the accurate thing to tell a customer is not "this voids your warranty." It is that the part they bought carries its own remedy to them, that a maker generally cannot void the equipment warranty just because a non-branded part was used, that a failure traceable to their part can be excluded, and that the labor to redo it is the piece nobody has covered yet, which is the piece the two of you have to agree about now.

The number that decides it: expected re-do hours

Price the risk, do not argue about the part. Two inputs, and one of them is the one shops never look at.

First, translate the forgone parts margin into labor-hour equivalents so the two sides of the comparison are in one unit. Say for this repair the margin you would have made on the part is worth roughly 0.75 of a labor hour to the shop. Second, work out what one re-do event actually costs in hours, which depends entirely on how hard it is to get back to that part.

Case A, accessible equipment. The install is 1.5 labor hours and the part is reachable in the same way the second time. A re-do event is roughly 2.0 hours, counting travel and setup. Break even where the expected re-do cost equals the forgone margin: 0.75 divided by 2.0 gives a failure rate of about 37.5%. Unless you genuinely believe better than a one-in-three chance the customer's part fails inside your labor warranty, installing it with a full labor warranty is not the disaster it feels like.

That 37.5% is a ceiling, and it is computed in a currency that flatters the shop. The 0.75 is margin the business keeps; the 2.0 is unbilled technician time you absorb, which is not the same thing. If your schedule is full, those 2.0 hours also displace 2.0 hours of sold work, roughly doubling the cost side, and the breakeven drops to about 19%. Use the lower one when you are booked out and the higher one when you are not.

Case B, the same part behind access. Now the component sits behind a finished surface, or inside a system whose charge has to be recovered before anyone can reach it. Getting back to it takes re-making the access, so a re-do event runs about 9.0 hours rather than 2.0. Same part, same margin, same customer. Break even: 0.75 divided by 9.0 is about 8.3%, and with schedule displacement it is nearer 4.2%. A failure rate that was comfortably survivable in Case A is now the difference between a profitable job and a job you work twice.

What flipped the recommendation is not the pedigree of the part. It is the cost of getting back to it. That is the variable to ask about first, and it is the one nobody asks about.

If the re-do involves recovering a refrigerant charge, that recovery is done into approved recovery equipment by a technician certified under EPA section 608, 40 CFR part 82 subpart F, which prohibits knowingly venting; that requirement applies on the re-do exactly as it did on the first install, and it is part of why the 9.0 hours is 9.0 and not 2.0.

What should move your assumed failure rate

You will not have a measured rate for a specific customer's part, so reason about direction rather than pretending to a number.

• Returnability. A part that can go back to a supplier if it is wrong or dead on arrival costs you a trip. One bought from a source with no returns costs you the trip and the argument.
• Spec class rather than spec sheet. Two parts can share a rating and differ in duty class, temperature range, or the medium they are rated for. Matching a number is not matching a part.
• Listing and labeling. Where the code your jurisdiction has adopted requires equipment to be listed and labeled, an unlisted part is not a risk decision, it is a decline. That requirement reaches you through the permit and the inspection, in the edition your authority having jurisdiction adopted, not through the standards body directly.
• Shelf age. Anything with a seal, a diaphragm, a battery, or a cure date has been aging since it was made, and a bargain part is frequently a bargain because of when it was made.
• Whether it is a protective device. A limit, a relief device, a pressure switch, or an overcurrent device is not an ordinary part. Declining is the default here, and if you are replacing one at all you first establish why the original opened, because a protective device that operated correctly is reporting a fault rather than being the fault.

The three positions, and what each one costs you

Install and warrant it fully. Cleanest with the customer, and the right call whenever the Case A arithmetic holds and the part clears the gates above. Say out loud that you are covering the labor, because a benefit nobody names is a benefit nobody credits you for.

Install and disclaim the labor. You install it, and if the part fails, the return visit is billable. This is defensible and it is where most shops land, but understand what you bought: you have moved the re-do hours back to the customer and kept the whole diagnosis argument. Write the disclaimer as a specific sentence naming the part and what is and is not covered, get it acknowledged before the install rather than at the door afterward, and expect to honor it in practice on the first failure or lose the customer over the principle.

Decline. The right answer where the part is unlisted, is a protective device, is a pressure-retaining or fuel-carrying component of unknown provenance, or where the Case B arithmetic says one failure costs you the job twice. Decline on the reason, not on the policy. "I cannot put an unlisted device in a circuit that has to pass inspection" is a reason a customer can accept. "We do not install customer parts" is a rule they will shop around.

Where your own warranty terms sit in all this

Your labor warranty is your instrument and you write it. What you cannot do is assume it means what you think without reading it: whether particular warranty disclaimers or limitations are enforceable, and whether implied warranties can be limited at all, is set by state law, usually through that state's enactment of Article 2 of the Uniform Commercial Code, and several states restrict disclaimers against consumers specifically. Have your own attorney review the wording once, then use the same wording every time.

How to find out whether your assumption is right

Nobody knows their real re-do rate, and it is the input the whole decision rests on. Measure it.

• Tag every install with the part source, shop or customer, as a field on the job. Two clicks, and in a year you have a rate instead of an opinion.
• Count re-dos by source over the same window, and state the denominator when you report it: re-dos per hundred installs of that source, not a raw count, because the two sources will not have the same volume.
• Separate part failures from diagnosis misses in that count. If you cannot separate them, that is itself the finding, and it points at what your notes are missing.
• Re-run the breakeven with your own numbers. If the measured customer-supplied rate is under your Case A breakeven and over your Case B one, you do not have a policy problem, you have an access-dependent policy, which is what most shops should have had all along.

References

• Magnuson-Moss Warranty Act, 15 U.S.C. ch. 50, a federal statute enforced by the FTC, for the limits on conditioning a written consumer-product warranty on the use of branded parts or service
• EPA refrigerant handling requirements, 40 CFR part 82 subpart F, including section 608 technician certification and the prohibition on knowingly venting
• Warranty disclaimers and limitations of implied warranties are governed by state law, generally through that state's enactment of Article 2 of the Uniform Commercial Code, and restrictions differ for consumer and commercial buyers; have your own attorney review your warranty language
• See related: How to Handle a Customer-Supplied Material Decision, The Parts Markup Conversation With Customers