The most expensive HVAC part I ever approved cost $62—not because the part was bad, but because of what happened after I chose it.
In March 2024, the McQuay rooftop unit that cools our back offices shut down on a low oil pressure fault. The service tech traced it to the compressor's oil pressure sensor. He laid out two options: the OEM sensor from the Daikin Applied parts desk at $218, available in two days, or a $62 aftermarket sensor stocked at a nearby Houston supply house. I told him to install the $62 one. Twelve weeks later, on a 96-degree June afternoon, the unit stopped cooling again with the same fault. The second repair cost roughly $600—after-hours labor plus the OEM sensor and freight. Add that to the first $332 visit and we spent about $930 to fix a problem that would have cost about $530 with the OEM part from day one. That $62 decision ended up costing us about $400 and one very uncomfortable afternoon.
If a part protects a compressor or touches a refrigerant circuit, find the right OEM part number before you start comparing prices. For components with clear specifications—capacitors, contactors, fan motors, relays, filters—aftermarket parts are often perfectly fine. The hard part is knowing which category you're in.
A note on who I am: I'm the office administrator for a 28-person medical office group in Houston. Since 2020, I've coordinated HVAC repairs for our three locations and ordered most of the parts. I process around 60 purchase orders a year across all vendors, and HVAC is a big slice of that. I am not a licensed tech or an engineer. My experience is based on roughly 15 McQuay-specific part orders and maybe 20 commercial service calls—a small sample, so take the specifics with some grace.
Why McQuay parts are easier to find than most people think
Before I learned how this industry works, I assumed McQuay was an orphan brand. It isn't, at least for most commercial product lines. Daikin acquired McQuay International in 2006 and later reorganized it under Daikin Applied. The McQuay name slowly disappeared from new equipment, but tens of thousands of older units with McQuay nameplates are still running, and Daikin Applied's parts and service organization still supports them for most major product lines. As of spring 2025, that support includes legacy part lookup for many chiller, rooftop, and heat pump lines.
The myth that McQuay is out of business persists because the name stopped appearing on new models in the 2010s. If you mention McQuay to a younger technician, you'll probably get a shrug. But "no longer a brand name" is not the same as "no longer supported."
A search for "McQuay HVAC replacement parts Houston TX" returns authorized parts distributors, local supply houses, and a few websites that look like they were built in 2004. I don't start with a search anymore. I start with the model number and serial number on the unit's nameplate. Even the official route will ask for those two numbers before they'll talk part numbers. It saves an entire afternoon.
The part-ordering rule I use now
I used to divide parts into "McQuay branded" and "everything else." That's not the right distinction. McQuay, now Daikin Applied, doesn't manufacture every component in its own factory. A compressor might be built by Copeland, a sensor by a controls manufacturer, a fan motor by a motor shop. What the OEM part number does is tie that component to the exact specification McQuay chose for that unit. That's where the value is.
The question I ask now is: what happens if this part fails? An oil pressure sensor is a protective component. Its job is to stop the compressor if lubrication pressure drops. If it fails, you either lose cooling on a hot day or you lose the compressor entirely. That's not the place to experiment with a part chosen by price tag. I can't say with certainty that the $62 sensor caused our second failure. What I can say is that I made that decision for the wrong reason, and it turned a one-visit repair into two.
The same logic applies to McQuay heat pumps. From my perspective, heat pumps get more interesting because they're often misunderstood. A McQuay heat pump is not just an air conditioner that runs backward. It has a reversing valve, a defrost control, and specific refrigerant behavior. If someone tries to substitute a generic air conditioning part without checking the heat pump's requirements, you can turn a small repair into a big one. For compressors, reversing valves, expansion valves, and control boards, I order by the OEM part number. For dual-run capacitors and basic fan motors, I let the tech use a quality generic if the specs match.
Anything that protects the compressor or manages refrigerant gets an OEM part number. Anything with a clear generic spec gets compared by price and warranty.
When I still buy generic: a small freezer and a bathroom exhaust fan
To be clear, I'm not an OEM-only buyer. Last year, the small freezer in our break room stopped holding temperature. The refrigeration tech tested it and found a failed start relay. The freezer manufacturer's relay was $70 plus shipping, and a universal relay from the supply house was $18. He told me the universal one is what most refrigeration techs carry in their trucks for that exact application. I told him to use it. It's been running fine since. Low risk, clear spec, and the consequence of failure was just a thawed box of frozen lunches.
Another example: one of our office bathroom exhaust fans got loud enough to hear from the hallway. I looked up "how to replace bathroom exhaust fan" and realized it was a straightforward job: turn off the breaker, remove the grille, pull the old motor, match the size and CFM, install the new one. I bought a $46 replacement motor from a big-box hardware store. No supply house, no Daikin Applied parts desk, no waiting. It took about twenty minutes. That part was never part of the building's HVAC system in the refrigerant sense. It just moves air through a small duct.
Some honest boundary conditions
This article is based on what we paid in 2024 and early 2025. Houston labor rates and shipping costs change, and part availability changes with them. If you're budgeting a repair, verify current pricing before you commit. What I paid for an OEM sensor in March 2024 may not be what it costs in June 2025.
Also, my experience is with light commercial equipment in medical office buildings. If you manage a 200-ton chiller plant or industrial refrigeration, the stakes are higher and the decision framework may look different. I can only speak to what I've lived through.
One more thing: if the repair involves opening a sealed refrigerant circuit, that's not a DIY job. In the US, technicians who handle refrigerants need EPA Section 608 certification. A bathroom exhaust fan is DIY-friendly. An oil pressure sensor on a rooftop compressor is not. The difference between those two worlds is why I still rely on a qualified technician even when I'm the one making the purchasing decision.
There's something satisfying about ordering a part that shows up with the right connector, the right setpoint, and no surprises. I used to resent the extra cost. Now I look at it as paying for certainty, and in Houston, certainty is worth a lot when it's 96 degrees in June.
