Historically my purchases of European car parts online have been from eBay sellers that provide a well-defined understanding of the origins of their product, clear photographs from multiple perspectives, and information that lets me know if the part meets or exceeds the standards of the vehicle manufacturer. That being said I have compromised these guidelines in the past, and my experiences - to put it delicately - have been less than satisfactory.
My Personal Experience with Volvo Tail Light Lenses
I will provide one such experience that may be helpful for those looking at tail lights and various lighting lenses for European cars, and how to avoid the mistakes that I have made in the past.
When I was rear ended in my Volvo 240 wagon and had to replace my tail lights, I could not find tail light units at the local salvage yards that were in good enough condition to install on my own vehicle. There were plenty of used tail lights on eBay, and they were oftentimes priced higher than new units from other eBay vendors. They were certainly in good condition, but the allure of having new tail-lights on the car after restoring the entire finish was to great for me to consider purchasing the older lights. Especially since the new lights were about twenty percent cheaper than the used ones, I went ahead and ordered them. This seemingly intelligent choice was, however, not so intelligent.
After using the lights for a week the plastic housing the incandescent bulbs on the brake light units actually melted through and caused an electrical short in my vehicle. I had thought that a bulb had burnt out - but it was actually melted plastic that caused a small electrical fire around my lenses. Now why would this happen - especially when using one-hundred-percent new lenses? The answer is although the lenses were an exact fit to my car, they were not designed to accommodate the heat of the 1156 and 1157 bulbs when the car was parked and the brakes and 1157 bulbs were fully illuminated. After about five minutes of stopped traffic, they completely failed.
Engineered Excellence from the Factory... What about anywhere else?
The engineers that designed your car have specifications that govern even the melting point of an unseen plastic part tucked away between your trunk liner and your lenses. Nearly all of the products perform to last the lifetime of the vehicle - and usually if they don't, then the rigorous quality standards of many manufacturers mean that recalls are made and products that aren't up to speed are replaced.
The engineers that design replacement parts (or rather reverse engineer) don't always have to meet the OEM standards of, say, BMW or Mercedes. They just have to sell lights that fit and look good and work for a bit so the car can roll away, say, from a used car lot having passed inspection.
In the case that I mentioned above, the lenses had been made "new" in Taiwan, and although they had met the OEM form with respect to how they fit, their function was compromised by this manufacturer in order to sell something cheaper on the market. The folks that made the product could have cared less about the temperature of the bulbs - they were more concerned about getting a product out the door.
A Simple Checklist to Ensure You Get What You Expect
If you are going to replace your lenses on a car that you plan on using every day - make sure to select products that will perform. Here is a checklist to ensure that you get quality product that will perform predictably as designed by the original manufacturer of the vehicle:
1) Verify either by contacting the eBay seller or reading the item description that the product is of OEM standards. Don't compromise on this point. Even used products may not be original, so it's best to verify before purchasing.
2) Find out who the original equipment manufacturer was for your car and see if that matches what you see in the listing. For example, Valeo of France and Hella make many lighting products for Volvo. If after reviewing who the original manufacturer was you see that a seller is passing something else off as OEM, you know what's going on.
3) Stay away from products and sellers that have negative feedback on a consistent or semi-consistent basis. If you have any doubts about the origin or quality of a product - make the decision to pass on the purchase.
4) Read forums and product reviews of the specific product if possible on third party websites. Often there are product reviews for aftermarket OEM or non-OEM products, and sometimes non-OEM products are over-engineered (but that is very rare). Check that what you're buying performs.
In short, just make sure that the lighting products you buy are designed for your application. It sounds simple, but it can be complicated. But if you take to heart the four steps listed above, chances are you'll be more than happy with your eBay purchase - even if you paid for a high-quality "used" product more than you would pay for an ersatz "new" one.