Dim headlight 02 Jetta (bora uk)

[1stjetta]

I have a dim left side headlight on my jetta. Originally I thought the bulb was bad so I replaced it. The light came on bright so I thought, problem solved. Since then, light is on but very dim. I removed and reinstalled the bulb thinking bad connection. Light came on normal. Switched to high beam, good. Back to low beam, back to dim. When I switch to high beam now, the bulb gets even dimmer (almost out) then returns to the dim look. I have been to the grounds under the battery box and actually removed and cleaned before reinstalling. Also checked the ground on the steering column under the dash but no change. Could I be looking at a bad relay?

[1stjetta]

One more thing that may be of help. The daytime driving lights are the same as night time, left side dim, right side normal.

[1stjetta]

Changed the daytime light relay today. It didn't help. While troubleshooting I came across what I think is an odd condition. The leftside bulb connector only has voltage on one hot wire at a time depending on high or low beam. Normal, right? The right side connectors however are both hot always regardless of high or low beam switch position but the headlight still gets brighter on high and lower on low. How'd they do that?

[neileg]

Sounds like an earthing problem to me.There are three terminals on the bulb since high and low beam have a common earth. If the earth is poor or non existant, the supply voltage to one filament will appear on the other supply terminal.

The earthing problem is likely to be at the headlamp unit itself, rather than in the switchgear.

[Eshrules]

Sounds like an earthing problem to me.There are three terminals on the bulb since high and low beam have a common earth. If the earth is poor or non existant, the supply voltage to one filament will appear on the other supply terminal.

The earthing problem is likely to be at the headlamp unit itself, rather than in the switchgear.

i agree... check your earths.

[1stjetta]

Can you tell me where the earth positions for the headlamps are located on the car itself. As I said before, I have already been under the battery box and all are good. Also checked ground under steering column. Thanks in advance for any help you can lend.