I ordered this vacuum pump switch from FCP Euro and thought I was ordering part number 31400608. When the part came in it’s actually printed as a 30645383.

The bag has the new number on it but it’s been ripped open and stapled close. I see from this website that these parts are actually considered cross referenced to each other https://www.ipdusa.com/products/13596/Brake-Booster-Vacuum-Switch-P2-XC90-Various-Genuine-Volvo-31400608-235366.

Am I right in assuming that parts with the newer numbers printed on them are the latest and greatest design and that an older number stamped part is basically older stock that had something considered suboptimal that the manufacturer decided to fix and alter the part somehow, keep its existing role and function, and issue an upgraded revision part number to reflect the new design. Is that accurate?

1 Answer 1


Yes. Parts can have different part numbers and still work exactly the same. OEM as well as aftermarket manufacturers do this, but who really knows why. Sometimes it's because the part itself has been updated. As an example, say a water pump had a new type of seal used to keep the liquids in, yet the overall there was absolutely no change in fit/function of the part itself. Another reason why there may be more than one part number is a part is used across different vehicle manufacturers, but is exactly the same thing. Something like a simple bearing might be a good example here. There can absolutely be different part numbers which encompass a part for many different reasons. It sounds like you've done your due diligence to ensure the part numbers have been cross-referenced to ensure it's the same part.

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    It's not uncommon for auto manufacturers to update PNs from one year to the next. A new part may be 100% interchangeable with the new one but have an extra mounting hole or something that makes it work with both models. So rather than stock two PNs they opt for just the more common one.
    – jwh20
    Aug 8, 2022 at 16:08

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