Terry's 2018 Audi Q5 rolled into the bay on a Wednesday afternoon with a broken headlight adjusting screw. That was the complaint. A little plastic screw. The kind of thing you'd expect to find in a hardware drawer, not on a repair order.
The complication? The dealer didn't sell that screw by itself for this generation. The "official" fix was a whole headlight assembly. A bill nobody wants. Meanwhile, the headlight was pointed at the ground, and Terry wanted to know why we couldn't just leave it for now.
That question—can't we just not fix that?—is one I hear almost every shift. But the answer is usually no. And that week taught me more about choosing parts than all the years I've spent inspecting them.
I'm the quality and compliance manager at an independent repair shop. I check every part that goes on a customer's car. Roughly 40 to 60 parts a week. So far in 2025, I've rejected 4% of first deliveries—fit issues, missing hardware, damage hidden in the box. I mention that not to impress you, but to be clear: I used to think aftermarket parts were a gamble. Hard to admit, but true.
The part that sat on my bench
Earlier that morning, a box from our parts supplier landed on my bench. A Dorman 911-900 intake manifold runner control for a customer's SUV in bay 2. The code pointed straight at the runner control. The OE part was on national backorder. Eleven days. The customer needed the car back in three.
The tech didn't ask for my opinion; he just started unpacking it. I stopped him. I don't care which brand name is printed on the box. I care what's inside the box.
Years ago, I wouldn't have stopped him to check. I would've told him to send it back. When I first started this job in 2021, I assumed any electronic part without an OEM box was a coin flip. Then a customer's car sat two weeks waiting for an OE sensor that arrived damaged on the truck. My "quality standard" had cost that customer a month without a car. Assumptions don't protect anyone.
So instead of rejecting the 911-900, I inspected it. Connector fit. Actuator geometry. Mounting points. Casting quality. I laid it on the bench next to the failed unit and compared everything I know how to compare. Then I checked the manufacturer's claims and warranty documentation—because per FTC business guidance, claims about a product have to be substantiated, and that's exactly what I needed to see. Everything lined up. I handed it back to the tech. "Send it."
Since 2022, every electronic part that comes into our shop gets the same bench check. Connector, housing, label, warranty paperwork. It takes about eight minutes. It has caught three parts that would've gone on a customer's car—a cracked connector housing, two bent pins. Eight minutes is a lot cheaper than doing the job twice.
The Audi Q5 that kept growing a list
Back to Terry. To reach the headlight adjusting screw, the headlight assembly has to come out. That means loosening the bumper skin. And once you can actually see the car, the job has a way of growing.
First, the serpentine belt. 76,000 miles. Original. The obvious side looked fine; the back of the belt told the real story. Cracks between the ribs. That's when Terry asked the question everyone eventually asks: how often should I change my serpentine belt?
Most manufacturers land somewhere between 60,000 and 100,000 miles. The practical rule at our shop: inspect at 60,000, replace before 100,000, and don't wait for either number if you hear a chirp on cold start or see cracks. A glazed, shiny backside is another red flag. Rubber ages even when the car doesn't. And a failed serpentine belt doesn't care where you are—it just leaves you there.
Second, the fuel pump. I asked Terry whether the car had been cranking longer than usual in the morning. He gave me that look. "Yeah. And there's a hum from the back, near the tank."
I hear this conversation a lot, so let's talk about fuel pump issues symptoms. They don't always show up together, but once they start, they tend to keep going.
- A whine from the tank area, especially after the car sits in heat
- A crank that's longer than it used to be on a cold start
- Hesitation or sputtering under load, like the engine starves for a second
- A lean code or fuel pressure code that doesn't add up at first
Terry's Q5 had two and a half of those. It was a matter of when, not if.
Third, the oil filter. If you look up an Audi Q5 oil filter, you'll find a cartridge-style filter—not a metal canister. It lives in a plastic housing on the front of the engine, and it takes VW-spec oil, not whatever was on sale at the quick-lube place. The car was due for a service anyway, and it made no sense to put the front end back together and leave a past-due cartridge in place. Plus, that plastic housing cracks if someone over-tightens the cap. We use the proper tool and a fresh o-ring. Small details, real consequences.
Fourth, the screw itself. A Dorman headlight adjusting screw is the fix here—a replacement for the one Terry's car snapped. That's the whole point of a part like this: fixing a broken screw without buying a whole headlight assembly. No OEM box. No assembly sale. Just the right piece, doing its job.
When the budget met the deadline
Terry looked at the quote and did the math a lot of people do. "The screw is what's broken. Let's do that and the oil now. Belt and pump in the fall."
I understood. Nobody likes a growing estimate. But I've watched fuel pumps strand cars in parking lots, and I've seen what a failed belt does on a busy highway. Part of me wanted to make the smaller deal and let the car go. Another part—the part that's rejected 4% of the parts that arrived this year—kept picturing Terry's daughter behind the wheel on Sunday.
That was the deadline. Sunday. The car was going to college.
Once a deadline is real, "we'll do it in the fall" changes meaning. It's not a plan anymore. It's a bet. And the odds were bad: an original belt at 76,000 miles with visible cracks, a fuel pump that was already singing, a runner control on the other car that had already failed. The time to replace a fuel pump is before it fails. Same for the belt. Same for any part that's already telling you it's tired.
So we did it all. And here's the part that surprised me: not one of those replacements was an OEM part. The fuel pump was a reputable aftermarket unit, on the shelf, backed by a warranty we'd actually read. The belt and filter were quality replacements our shop trusts. The headlight screw? Dorman. The 911-900 going into the SUV? Dorman.
That's the lesson it took me four years to learn. The box isn't the guarantee. Availability, inspection, and warranty coverage are the guarantee. OEM is a great choice when it makes sense. But OEM stopped making sense the moment it was eleven days out and the customer was leaving Sunday.
What Friday sounded like
Both cars were done by Friday afternoon. Not just done—finished. I test-drove the Q5 first. Bright, level headlight. Quiet pump. Silent belt. I let it idle and listened to that particular quiet. It's the sound of a problem that didn't get the chance to become a story.
Then the SUV in bay 2. The intake manifold runner control installed clean. No codes. Smooth idle. The Dorman 911-900 did exactly what it was supposed to do. No drama. No noise. Just a working part.
That was the clearest side-by-side comparison I've ever had: two cars, two non-OEM parts, zero problems. And one teenager parked safely at school on Sunday night.
If you take one thing from this, take it from someone who opens boxes for a living:
Certainty costs a little more up front, and it's still the cheapest thing in the whole transaction. Fix it while it's still a small story. If you wait until it's a big story, the car fails at the worst time—and then you pay for certainty and a tow truck.
I still have mixed feelings about aftermarket electronics. I'd rather put the factory part number on a car when I can. But when the factory part is on backorder, and the alternative has been inspected, verified, and warranted? The "factory choice" isn't automatically more certain. Sometimes it's just slower—and a lot more expensive.