I owned a 2009 Audi A3 with a rear lightbulb error that eventually led to a lightbulb failure. For months there was a nagging error icon on the instrument panel that indicated one of the rear brake lightbulbs was out. When I finally checked, I found that all the brake lights on the rear of the car were working, even though the indicator displayed a problem. On a subsequent check, I found that two of the bulbs had burned out.
With the annual safety inspection looming, and half the brake lights not working, I finally had the incentive to fix the problem.
When I removed the rear light assemblies, I discovered that the non-functional lightbulbs were still good. The bulb holder assembly is a three-dimensional injection molded plastic unit that combines with a three-dimensional formed galvanized steel sheet metal frame that serves both as a structural holder and electrical conductor. The sheet metal frame is swaged to the plastic structure by thermally melting six studs.
Two years in the Texas heat had raised the temperature of the plastic to a level that the creep strength of the plastic was exceeded. The two bulbs that didn't light were in an assembly where the plastic actually flowed between the sheet metal holder and the ground cylinder of the lightbulb. The steel frame had raised about a quarter inch off its intentional mounting and tilted, allowing the ground frame to contact plastic and initiate the plastic melting. That broke the circuit.
The dealer was out of stock on this assembly, which was just as well. The price of each assembly was about $100 with tax. So I decided to break the studs off, then drill pilot holes for #4 sheet metal screws to replace the swage studs. All the lights now work perfectly, and the instrument status error has been eliminated.
While I admire the simplicity of the design, its execution failed under conditions that should have been within the designer's requirements. It isn't clear whether the sub-tier supplier cheated by using the wrong plastic, or if this is a common design flaw, which has gone unresolved over the five-year production run of this model.
This entry was submitted by Kirk Miller and edited by Rob Spiegel.
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While plastics have come a long way in the last decade or so. there are just certian components that exceed the capabilities of even the best plastics. Light bulb assemblies in this case are a classic example. Had the manufacturer chosen LED lights instead of high heat conventional bulbs, this may have worked fine. Apparently verification testing has gone by the wayside in favor of cost cutting.
Other components that makes me nervous are plastic valve covers and intake manifolds. they may work fine for a few years until the warranty expires, but eventually time and thermal cycles will do them in, leaving the owner footing the bill for replacement parts.
"Re UK temps, parts of northern Scotland are pretty darn cold in the winter, down to an average of 1C or below, but that may not be low enough for testing purposes."
1 deg C? Oh no, that's not nearly cold enough! 1C is almost considered tropical in some areas of the north! When it warms up to above freezing for the first time in the Spring we start wearing T-shirts, really! -40 is the typical cold standard. Most car manufacturers have a hot and cold weather proving grounds. GM's cold weather proving grounds is in Kapuskasing, Ontario, Canada.
J-Allen thinks the engineer should be publically whipped. I think the engineering (and higher) management needs to be tortured.
I've been involved in too many projects where NO time was allocated for testing/debugging. If the thing looks good the first time the management is ready to move on. I'm all for designing something as close to the final product as possible but a lot of engineering departments already have the NEXT project to shift you to and leave no time for a second rev.
I suspect that the plastic compound that ended up in the tail light assy. probably cost 10 cents per pound less than the one they had been using for 20 years.
Thanks, thrashercharged, I didn't really think 1 deg C was low enough based on what Chuck and others had said. Now I'm curious--where are you writing from?
When I started out, my first professional job was working in an automotive paint lab in Detroit. Knowing that the cars would experience the combo of salt and humidity in climates such as Florida, we did saltwater testing on the paint. Seems a no-brainer to test for all of the potential environments customers will use the products.
When I started out, my first professional job was working in an automotive paint lab in Detroit. Knowing that the cars would experience the combo of salt and humidity in climates such as Florida, we did saltwater testing on the paint. Seems a no-brainer to test for all of the potential environments customers will use the products.
I was surprised to see that this failure was on an Audi. Audi is a high dollar vehicle that you would not expect to see a failure like plastic creep. Unfortunately, limitations of plastic as compared to metal are not always taken into account when metal replacement projects are completed.
It isn't just Audi or Vw etc they also do the same stuff in Mercedes. I just replaced the dash light bulbs ($1 at Napa or $20 from the stealership same bulb, same brand etc) and the sockets were either scorched or melted. Of course the dealer er stealer will tell most customers that they need a new dash assembly (don't have enough room to put the price of that in one post). Unfortunetly it seems most customers are of the type that they can fix anything using only a credit card or checkbook and the problem goes away. Some of the rest of us who have an idea whch end of a screwdriver or soldering iron to hold are converting to LED's. That isn't as straight forwards as it seems. Mercedes has designed the systems so that they detect the current load so if you don't get things right you get light but still get a light out light unless you are lucky to have that one burnt out as well !
Funny all through school up to university not one person ever told me there are monkeys in Germany ;-]
BAD NEWS.. not only Audi but also ANYTHING... CHRYSLER; it happens to the Caravan, Voyager, Jeep Cherokee... the double filament rear light bulb that act as Rear lights and Brake lights, is mounted in a plastic bulb holder that has a bayonet style mount into the rear lamp assembly connected to the car electric system, well the bulb holder has 3 sliding contacts that touch the lamp assembly, well it seems that the current flowing to the bulb, gets the whole thing hot enough to scorch the bulb holder and melt the lamphoder where the contacts touch, resulting in NO brake light or tuning light or working rear lamp === DEALER solution : to replace (BUY $) the whole rear lamp assembly. ...
Talking about monkeys designing stuff... ! ! ! planned obsolescence, or plain stupidity.
My solution... solder 3 wires (1 regular rear light filament, 2 brake light filament and 3 ground) to the lamp holder, and connect them directly to the electric system wires spliting the insulation were the wires go into the connector. you have to know what you are doing but it solves the problem and works forever.
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