Should you supply your own parts to your mechanic?

an assortment of car parts against a grey background

We know and realise that maintaining a modern vehicle can take a big bite out of your disposable income, and particularly so when your vehicle breaks down unexpectedly. This can happen to almost anyone at almost any time, and while we understand that you might want to supply your own parts to reduce costs, doing this is not a particularly good idea, and here is why-

You don’t always know what you are getting for your money

There is no escaping the fact that the global aftermarket parts market has become flooded with parts of uncertain origin and quality in recent years. Australia has not escaped the flood of substandard parts, and while the aftermarket car repair industry has made great strides in identifying the source(s) of substandard parts, it is impossible to prevent the flood of fake parts completely.

Unless you are a professional mechanic, it is sometimes very difficult to tell good parts and bad parts apart, which means that there is a high likelihood that parts you source by yourself may not be fit for their purpose. However, there is a little more to this issue, so let us look at the main reasons-

Why you should trust your mechanic to source parts for you

There are many examples of parts that may appear to be identical in all respects, when, they are in fact, calibrated or programmed differently to suit different applications. Examples of this include electronic control modules, wheel speed sensors, some wheel bearings, exhaust gas recirculation valves, turbocharger boost-control valves, and many others that will fit on several vehicles, but will not perform as expected if they are fitted to the wrong vehicle.

Moreover, some parts suppliers will not exchange parts or refund you if you bought the wrong electronic part(s), but which they supplied correctly based on the information you gave them. So how do mechanics know the difference between the right parts and the wrong parts for your particular vehicle? Here is how-

They buy from trusted suppliers
Car manufacturers typically do not make or market spare parts; third party manufacturers are usually authorised and licensed by carmakers to manufacture parts to specifications provided by said carmakers. Therefore, in practice, a parts manufacturer will supply parts in bulk to carmakers to support both vehicle assembly processes and to support dealer workshops.

Nonetheless, the important thing to bear in mind is that parts manufacturers also supply the aftermarket with parts that are often identical to the parts they supplied to car factories and dealerships. This means that in many cases the only difference between a licensed part supplied to a car factory or dealership and a licensed part supplied to a reputable aftermarket parts wholesaler may be the packaging.

Mechanics know what to ask for
In some cases, such as electronic control modules that can potentially be pre-programmed with different versions of operational software, the actual part numbers of most control modules are linked to the vehicle’s VIN (Vehicle Identification Number) to ensure that the correct software version is programmed into the module.

Other, more common replacement parts, however, can sometimes have more than one series of identifying numbers and/or letters. In some cases, one identifying number might serve to identify the actual part, while another identifying number or mark may limit the use of the part to specific vehicles or models within a model range.

Thus, if you are not sure what you are asking for in the parts shop, you could very easily end up buying the wrong part.

Mechanics know fake parts when they see them
While the ridiculously low prices of some parts can be taken as clear evidence that the part is a fake, there are other, equally telling signs that a part might be suspect, and your mechanic has seen them all. These signs include but are not limited to-

  • Unbranded packaging, or obvious spelling and/or grammatical errors on the packaging
  • Poor surface finishes on some parts
  • Obvious differences in weight between good parts and fake parts
  • Parts don't fit correctly or don't fit at all

These few pointers should give you a good idea of how easy it is to buy the wrong or unsuitable parts, but there are other, equally important reasons why should let your mechanic source your parts. Here are two of those reasons-

Repair work and/or parts might not be covered by a warranty

The problem with manufacturer’s warranties on parts is that, a), they typically only apply to the original purchaser, and b), that manufacturers’ warranties on parts can be voided if a suitably qualified mechanic did not fit or install the parts in question.  In practice, this means that even if the parts you source are covered by a manufacturers’ warranty against defects in materials and workmanship, that warranty cannot be transferred to the workshop that will fit the parts you handed to them.

If a workshop does agree to fit a part they did not source, they may exclude the part from their express warranties. In regards to Australian Consumer Law, the workshop will not be obligated to provide any guarantees applying to the part (as they are not the supplier). Instead the guarantees provided will be limited to the service of fitting the part. Meaning when the parts you source fail, you may have to pay for new parts and the associated labour costs to have them fitted professionally- again, and in addition to perhaps paying to repair damage caused by the parts failing prematurely.

In some cases where a mechanic has taken the approach above and customer-supplied parts have failed, the mechanic can sometimes still end up shouldering some of the responsibility/blame and it is for this very valid reason that many reputable mechanics will not fit customer-supplied parts.

Your safety might be compromised

It is very difficult to draw clear distinctions between parts on modern vehicles that are safety-critical, and others that may not be directly associated with the safety of a vehicle's occupants. This is especially important given that the safe operation of a modern vehicle depends not only on correct and efficient interactions between numerous systems but also on the correct operation of hundreds of parts and even entire categories of parts that did not exist as recently as 20 years ago.

Given that the replacement of just one part by a suspect or substandard part could potentially make your vehicle unsafe to drive, can you think of even one good reason why your mechanic should not be trusted with sourcing all the parts they need to perform a professional repair or service on your vehicle?

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