Lost a low beam....any clues?

The other day I lost a low beam on my drivers side. (01 alh jetta 280,000 miles). Thinking it was a bad bulb, I ran to the local napa and replaced it. Not the problem. The light comes on when i flip the high beams, but goes out on low beams and drl. All the headlight fuses are still good. Now I'm puzzled. Can anyone give me a clue? I'm thinking a bad plug for the bulb?

Yes, remove the headlight connector and check. Might also want to check all the connections in the fuse "box" sitting on top of the battery (CAREFULLY!).

Check the replacement with a VOM or 12V power source. It could be DOA.

Are these stock lights? I had issues with cheap chinese knockoffs... the wiring and harness were too small to handle the voltage and heat. I ended up replacing the wiring.

You have to check there is 12 volts to the headlight that's out and the ground side is good.
The high beam works so the ground should be OK
If 1 low beam is working the switch should be OK
Check if there is power on both sides of the 2 low beam fuses.
If OK start tracing where the power is lost from the fuse box to the head light.
Having the wiring diagram is helpful with this, it gives you the color of the wires you have to trace.

(I am guessing) if the bulb comes on with high beam, the low beam wire is touching the high beam wire, somewhere such as inside the headlight housing. When the high beam is off, low beam gets no power. The wire casing on my stock headlight wires were fried from the heat, exposing the wires and shorted my low beam. It thats the problem, Fixmyvw has wire replacements for the headlights.

Had this issue with my 01 Golf. RHS low beams were going out waaaay to frequently. After a few bulbs, I tried a removed one and it was fine. Turns out it was the connector plug to the head light assy( on the inboard side of the back ). Un-plug, plug it back in, and now no issues...
cheers,
Douglas

An update now that my growing season is over and I finally found time to work on this issue.
Electrical is not my forte, so I'm a little unsure as to how to test power from headlight plug to the fuses and beyond. I did cave in and order a complete headlight wiring harness from aarodriguez, with no sucess. Now i have replacement headlight connectors and wiring.

I swapped the low beam fuses to see if one might be faulty without being completely shot, but I still have the same problem.

I guess my challenge is figuring out how to test for power at the headlight plug. I understand there are 2 pins for the low, and 2 for the high. Power and ground? My thought is if i touch one lead to the low beam pin, and one to the ground pin, i should register 12v on the meter? Can someone call me out if I'm being a dumbass on this?
Also, how does one go about testing for power on either side of the fuses?

At a minimum you need a test light for this.
Unplug the cable at the headlight assembly.
Connect the test light clamp to the battery negative.
With the key and headlights on pin 7 should have power to it, light will light. It should be a yellow wire with a black stripe.
If there is power there go to the next section further down.
If not pull fuse 21 in the fuse box when you open the drivers door. Should be 15 amps.
Test for power at the 2 connection inside the slots you took the fuse out of.
I use 'T' pins to get into tight spots or a straight pin in a pinch. Short piece of thin wire if you have it.
One side should have power.
The other side goes to the headlight bulb.
Fuse 21 is the left low beam fuse for my 03.

If there was power to the headlight plug:
Clamp the test light to the battery positive terminal.
Touch the probe to headlight socket pin 4.
It should be 1 of 2 brown wires.
The light should light. If not trace the wire to where it grounds on the body.
Should be close to that area.

The funny thing, I did not know the high and low beams had separate grounds.

Hope I made this clear.

Known problem in a stock light bulb wire harness for the (900x) style bulbs (I thought it was 9006 or 9004 but either way, the connector is a sloppy pentagon shape. You need to access the housing, find the connector that plugs directly into the bulb and inspect it for voltage/damage. Usually it's got evidence of being burnt or severed but the connector will look like the low-beam terminal is still there and okay so you have your high beams work but not the low beams. Most auto parts stores can sell you a replacement harness and all you have to do is rewire the harness to the stock wiring (solder and shrink wrap recommended).
Hope this helps.

a friend of mine is having the same issue but with the high beams on his 03. i will be keeping an eye on this thread.

moparvwfrak said:

a friend of mine is having the same issue but with the high beams on his 03. i will be keeping an eye on this thread.

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Has he checked the fuse with an ohm meter?
Could look good and be bad.
Next check for power getting to the plug at the light and it's not melted or such.
Last check the ground from the plug at the light has continuity.

Bend the tabs tighter/closer in the bulb socket