There are many reasons why an automotive repair shop will not install customer supplied parts.
Liability, Warranty, Reputation, efficiency and Profit.
When a business installs a customer supplied part they are accepting the liability regardless if the failure is caused by the part itself or improper installation of said part. Due to the litigious nature of our society this becomes a very large risk for the business. There are no waivers a shop can print and have the customer sign on the repair order that will limit the exposure to the business. In fact, the very nature of a business typing a disclaimer on a repair order is a basic admittance that they know there is a higher risk of failure. It doesn’t matter if the consumer purchased the part from a new car dealer, online, a parts warehouse etc… In the eyes of the court the shop/technician is the professional, he/she was the last one to put their hands on the part and should have known if that part was not good quality or that the part was going to fail.
If a shop installs a part that they did not supply and that part fails, the finger pointing begins, the shop will state that the part is defective and the parts warehouse will say that the part was not installed properly no matter how simple the job. Now the consumer is stuck in the middle because the shop doesn’t want to do a job the second time for free (although they are required by law to do so as stated above) and the parts warehouse doesn’t want to pay for the labor for the shop to redo the job. They only sold the part and will only replace said defective part.
In a perfect world, no parts would ever fail no matter where they came from. Unfortunately, this is not the case. If a part is installed and that part fails, the customer will have a poor experience with all parties involved, the shop will be unhappy because they now have to do the job a second time for free and pay their technicians because by law they can’t make the technicians work for free. That customer will then share their experiences with friends, family, social media and online review sites. Businesses work very hard to build their reputations by providing good customer service experiences…so why would a business take the chance of ruining their reputation?
In a perfect world, every part is a perfect fit. If a technician has a car torn apart and the part either doesn’t fit or is the incorrect part than the efficiency of that lift that is now tied up until the correct part is delivered. Who will cover the loss revenue of that lift for the time period of which the lift is unusable? If the customer has to have the car back that day but the parts supplier the customer bought the part from can’t deliver the part until the next day, who is going to pay the labor for the technician for taking it apart and putting it back together even though no new part was installed?
This is always a sensitive subject but it needs to be addressed. In order for a business to remain in business and provide the latest needed tools and equipment as well as training for the modern complex vehicles and provide competitive compensation for talented technicians they need to make a profit. For most auto repair shops 50% of their revenue comes from the gross profit generated by the sale of parts. Labor alone is not enough to cover the expenses.