This is one of the most-asked questions among all aftermarket product manufacturing queries.
From the Federal Trade Commission:
“No. An ‘aftermarket’ part is a part made by a company other than the vehicle manufacturer or the original equipment manufacturer. A ‘recycled’ part is a part that was made for and installed in a new vehicle by the manufacturer or the original equipment manufacturer, and later removed from the vehicle and made available for resale or reuse. Simply using an aftermarket or recycled part does not void your warranty. The Magnuson-Moss Warranty Act makes it illegal for companies to void your warranty or deny coverage under the warranty simply because you used an aftermarket or recycled part. Still, if it turns out that the aftermarket or recycled part was itself defective or wasn’t installed correctly, and it causes damage to another part that is covered under the warranty, the manufacturer or dealer has the right to deny coverage for that part and charge you for any repairs. The FTC says the manufacturer or dealer must show that the aftermarket or recycled part caused the need for repairs before denying warranty coverage.” Source: http://www.ftc.gov/bcp/edu/pubs/consumer/alerts/alt192.shtm
Accessed: 8/30/2012
For more information on the Magnuson-Moss Act and how it affects you, check out: