A part number is the fastest way to confirm you are getting an exact match. Here is where to find one, how to read it, and what to do if you can’t.
Where part numbers usually appear
Part numbers are printed, stamped, engraved, or molded onto many parts. Common locations include:
- Electronic modules, sensors, and switches: A printed label on the housing, often with a barcode.
- Alternators and starters: A label or stamped tag on the case.
- Headlights and tail lights: Molded into or printed on the back of the housing.
- Plastic trim and body parts: Molded into the back side of the part.
- Wheels: Often cast or stamped on the back of a factory wheel.
- Hoses and lines: Sometimes printed on a tag or along the hose.
- Metal brackets and castings: Stamped or cast into the metal.
Tips for reading a part number
- Clean it first. Grease and road grime hide numbers. A little degreaser and a rag go a long way.
- Use light and a mirror. A flashlight at a low angle makes stamped numbers easier to read; a small inspection mirror helps in tight spots.
- Take photos. Photograph the number and the whole part from several angles. Photos can be emailed to your parts supplier.
- Write down everything. Labels often carry several numbers. Note all of them — the right one is not always the largest.
Part numbers vs. casting numbers
Many metal parts have a casting number formed into them during manufacturing. A casting number identifies the raw casting, not necessarily the finished part — the same casting can be machined or assembled into different final parts. It is still useful information, but it is not always the same as the part number.
What is a superseded part number?
Manufacturers sometimes replace a part number with a new one — for example, after a design update or a change in supplier. The new number supersedes the old one. If the number on your replacement part is different from your original, it may simply be the updated number. Your parts supplier can confirm.
OEM numbers vs. aftermarket numbers
OEM parts use the vehicle manufacturer’s numbering. Aftermarket brands use their own numbers, and catalogs cross-reference them to OEM numbers. When you share an OEM number, it can be used to find matching aftermarket options, too.
What if you can’t find a number?
That is common, especially on older parts. Your VIN plus your year, make, model, trim, and engine is often enough to identify the part. Photos and a description of where the part sits on the vehicle help fill in the gaps.
Send us what you have
Call Rock Sales Parts at +1 646 244-2586 and read us any numbers you find, or include them in an online parts request. You can also email photos to rocksauto9@gmail.com.
Need help finding this part?
Call with your vehicle details — we will help identify the right part and let you know what we can find.