frustrated

So I turn on my headlights, up they pop but only the driver side works on dipped beam although both work on main beam. Drive a mile down the road and the passenger dipped beam comes back on. So I check all the connections I can get to and change the bulb but it does the same thing every day. Bang on the pod or wing, flip the pods up and down a few times, drive over a pot hole in the road or a speed bump- all to no avail It just comes on itself after about a mile. It cannot be the temperature of the wire as that would work the other way around and the battery voltage is fine, Would anyone have any ideas before I start ripping pods and wheel arches out next weekend?

jwbeck17

No immediate answer here, but I have suffered from a similar issue. Upon inspection in noticed that the passenger headlamp connector had been replaced and soldered. I cleaned the connection there and made sure the solder was good.

Other thing i did was clean the CE panel thoroughly and used Deoxit. I noticed the issue right after i cleaned it but seem to resolve quickly and hasn't reoccured since.

My thought is that the issue may be with the headlight relay, which is a double relay on the right side of the CE panel.Maybe a few taps on it may work or flag that it needs replacing. I haven't been able to test the theory since mine has been working well for me for the past month or so.

Good luck and let me know what you find out.

WallyP

ALWAYS helps to know the model year, etc...

Check the fuse contacts for the passenger dipped beam.

OTR18WHEELER

I also have a similar issue once in a while with only the pass side headlight, but mine resolves itself with turning the lights off and then on again. hitting the lamp never worked, and it is not the plug or light.

Mrmerlin

if the fuse is good and the bulb is good the next culprit is the harness attach point directly under the headlamp this harness is clamped with a sheet metal fold clamp and after many cycles they the wires shear.

The best thing to do is fix the wire,
then make sure there is enough wire when the light is in the up and then the down position.
then lightly bend the clamp to fix the wires

frustrated

Sorry! Should have said. Its an 89 S4 euro. so RHD. The headlamp fuses are on a fairly new separate board having melted the original by putting illegal high wattage bulbs in a while back So that area should be fine but I will check anyway. I reckon your suggestions of the relay or the harness attach point are probably favourite. will give them a look. Many thanks all.

Alan

Leave the relay alone - it cannot be this. The relay has a single output that drives both headlamps in either the high beam or low beam modes. So - if one side still works OK it is certainly not the relay. There are separate fuses of course and separate wiring.

This is most likely either an issue in the wiring into the pod (look where it flexes for damage), plug connectors or at the fuses - since you worked on the fuses - I'd start there...

Alan

frustrated

Thanks Alan. Will check fuses again as a fair amount of condensation in the car due to a recent rubbish tailgate seal.

Mrmerlin

put a fan in the car with the windows down and parked in the sun remove as many of the carpets as possible

jwbeck17

How does the combination headlight relay work? I assumed that the left XXIII part of the relay ran the hi/lo for the left light, whereas XXIV right relay covered the hi/lo of the right headlight. A total assumption, so I welcome your insight since I wondered about that one.

Alan

Your assumption is not logical since there are 3 states for each lamp: off/high/low - clearly one relay could not provide that... There is no left or right side to this relay - it is a double-wide (it takes 2 slots) however it actually contains up to 4 embedded relays.

It would take a very long time to explain exactly how it works - however here are the 3 or 4 relay functions in the HL relay:

Relay 1 controls the headlamp on/off (for both sides)
Relay 2 controls High/Low Beam switching (for both sides)
Relay 3 (& 4) control the pod motor drive*

*Just 1 relay for the motor drive in 1977-1986 cars (motor only rotates one way)
*2 relays for the motor reversing drive in 1987-1995 cars (reversing motor)

The functions of relays 1 & 2 are really quite clear in all the wiring diagrams, the motor drive is more complicated to understand.

Alan

jwbeck17

Alan, as always, your attention to detail is greatly appreciated! I swear I read somewhere that the double-wide relay was a left right combo, but I probably got it from an incorrect product description on a third party site. If it was, I would suspect there would be two single relays instead of a combo one.

The important thing is that this double relay is not the issue here, and that is helpful for me to know as well. Thanks!

frustrated

Only just managed to sort out my lights due to weather and work. So Alan you were right, it was a bad connection on the new fuse holder. Although to be fair it tested ok and I only really found it when the wire melted on a 50 mile run. Have changed both headlight fuse holders and leads for heavy duty ones with 7.5 amp fuses. All ok so far. Thank you.