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Sorting those facelift halogens

lothian Oct 18, 2009

  1. lothian

    lothian New Member

    Ok, this is kind-of related to a number of previous threads on the subject of headlight performance so apologies if you’ve heard it all before.

    My ’99 A4 2.8 Quattro suffered from appalling dipped beam performance. To be honest, the front fogs were more use than the dipped beams – that bad!

    I cleaned up the terminals and reworked the alignment to achieve the kind of lighting you’d get from a 1970’s car on ball bulbs. An improvement but woeful compared to my Mk 4 Golf.

    In the past, I’ve had problems with the wiring and switches degrading over time on a number of VWs and Audis so I checked out the circuit with a trusty volt meter. With the engine running, I was getting 12.5 volts on the back of the lights and 14.5 volts at the battery. That’s a 2 volt drop – totally unacceptable!! I’ve heard auto electricians prefer to operate within a 2% drop.

    One thing we definitely do know about halogen lights is that they are particularly sensitive to voltage drop.

    To reduce the voltage drop, I could have replaced my switch and wiring, the best option for keeping the car original, but no guarantee of improvement. The second option was to introduce relays and have the juice going from battery to bulbs in the most direct way possible. I opted to fit the relays.

    I kept the original circuit pretty well intact (in case I need to revert). I pulled the positive terminals from the back of the dipped beam units to act as a switch for the relays. I bolted the two relays to the plastic wiring cover clipped to the power steering reservoir. My two fused positives were routed from the battery +ve terminal through the brake pipe grommet then passed through a new conduit along the nearside engine bay to the relays.

    The only ‘modification’ I needed to make was two small holes in the headlight terminal covers. I couldn’t use the existing terminal block as I was using much heavier cable than the OEM block could cope with. I retained the standard earths from the bulbs but plan to beef these up later.

    The result –well I’ve not seen that much light in front of my car for a long time:icon_thumright:. I’m not saying this solution is for everyone and some say that it isn’t a good idea to fit old fashioned relays to a modern electronic car. For me, it’s a cost effective and legal solution.

    So I now have facelift headlights that work as well as look good.
  2. jcb

    jcb Active Member VCDS Map User

    nice work.
    I got some HID's as I am **** with wiring.
    seriously bright lights now

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