Tail lights keep failing on Golf

I find that the lights in my daughters 2003 Jetta GLS fail far more frequently than any other car I have ever owned.

However, 5 days is a bit too fast :)

Sounds like you have a voltage problem.

If you have a multimeter, start the car and measure DC voltage across the battery while the car is running. It should be 13.0 to 15.0 volts or so depending upon temperature. If it's over 15.0 volts, you might have a bad alternator/regulator.

Are you certain you are using the correct bulb?

Maybe maybe not. I would also consider the possibility of water leaks or vibration. You also may want to consider changing brands. You may have hit a supply of defective lamps.

Even 15 is high. Most voltage regulators at the alternator itself will limit it to 14V.

Others might fail eventually but since taillamps are usually relatively dim (5-10 watts usually) their filaments are thinner and are probably more susceptible to oversupply of voltage.

You should get a test meter. Pull the bulb trays out and pull the taillamp bulbs out. with the engine running and lights turned on you should get no more than about 14V at the center terminal in the bulb socket (12-13 volts I bet is typical, but definitely no more than 14).

VW alt voltage falls in the 13.6- 14.1 volts.

Check the connections to the tail lights, including the ground. If the connections aren't tight, they could be flickering, which isn't good for bulb life. Might want to make sure the brake light switch isn't adjusted too tight and making the lights flicker too.

Mark '95 Jetta GLS

make sure the tension is good on the bulbs also. If they are loose they might flicker, like Mark says, due to bouncing around and then fail prematurely.

If it is a high voltage problem -- which seems plausible to me, too -- then I think you have proven that taillights are the bulbs that are most susceptible to failure from high voltage. All the other bulbs may or may not fail from it, but one thing's for sure, the most-susceptible bulbs will fail first.

That is correct....

if high voltage is the cause, I would expect that the little 5W parking lights in the headlamps have probably failed and most likely the 5W side marker lamps in the sides of the front bumper...have these also failed? These are all little dim bulbs with small/tiny filaments. If this logic holds true (that low-wattage bulbs are more vulnerable), they're probably dead as well. But to ultimately prove the problem you need to get a test meter on the alternator w/the engine running and everything else shut off and see what the voltage reading is. Should be constant in the high 13Vs and if the engine is revved it shouldn't go up significantly, if at all. if it's too high (or goes up a bit when revved), you have a bad voltage regulator.

That's not what I said. I said, the most-susceptible bulbs will fail first. You're assuming a link between most-susceptible and low-wattage.

If the problem is high voltage, and the taillights failed before any other bulbs as a result, then the only conclusion is that taillights are the most susceptible to failure from high voltage.