£5 headlight solution

[J.C 10]

I've been doing some research on the dim headlight problem, I know you can get looms which work BUT being a cheapskate and having a bit of time on my hands, I looked into it,

 

Now it's generally been said that it's the length of the wiring which cause the voltage drop but generally it's the switches which cause a drop in voltage, this was my presumption and I carried out the mod and THEN did some measurements (which I will reveal later)

 

So if you believe the wiring doesn't cause most of the voltage drop, then why modify the wiring from the fusebox to the lights,

so I kept that standard,

 

So I presumed the 2 switches (Headlight and full beam) were the cause of the Voltage drop, I studied the wiring diagram and decided it would be nice to install a relay on the fusebox for the lights, the available ones were relay position 1, 5 & 7,

 

Now I'm planning a mkiv climatronic aircon install so position 1 (Aircon relay) was ruled out, position 5, (Coolant buzzer relay ) couldn't handle the current the lights take,

So it left relay position 7 (Headlight washer relay)

I ordered 2 relays off ebay for less than £5 delivered, I ordered 2 to keep a spare in the car,

 

So now to the wiring,

 

I cut the yellow wire from the headlight switch (via full beam switch) 20cm from Connector J/3, I then soldered(you can crimp if you've got a good set of crimpers) a female spade connector onto the end from J/3 and then covered in heatshrink, this goes to terminal B/6

 

The yellow wire from the switch(s)gets a small female spade connector, heatshrink sleaving, this goes to B/1

 

Next you need to get a negative to terminal B/4, I did this by using a 10cm piece of wire from an old loom I had lying around, The reused connector "locks" into place in terminal C/3 and then a small female spade connector to B/4.

 

To supply battry voltage to the relay I made up a 30cm long heavy duty cable (from old loom again) and soldered female spade connectors on each end,

this wire goes from B/5 to Y/2, someone had previously used Y/2, so I relocated that wire to a spare battery voltage terminal (big red plug with 4 small male spades in it, next to connector J,

 

The relays haven't turned up yet but that didn't stop me from trying it out,

first I connected a jumper wire between relay pins 2 & 5, this in effect reconnected the (cut) yellow wire, I measured this (Jumper wire) voltage as 11.02V with lights on (engine off)

The voltage at the headlights was 10.50V, so the wiring from the fusebox to the lights creates a 0.5 Volt drop,

Battery voltage at fusebox is 12.50V, so the 2 switches cause a voltage drop of 1.50V.

 

next I connected the jumper wire between relay pins 2 & 4, this simulates the relay contacts being closed, this Voltage was 12.50.

 

With the engine running,

battery voltage 13.8V

old system voltage at headlight, 11.10V

new system (relay simulated) voltage at headlight, 12.65V

I've gained over 1.5V but still losing 1.15V

so it's not as good as the loom, But it is cheaper

 

Relays should be here tomorrow, and I'll simulate the relay tonight when it's dark,

 

I've got photos but having trouble uploading them on here

Thanks for taking the time to read.

Steve

Edited September 18, 2013 by J.C

[tony_ack 0]

The only thing that I'd say is that a loom is pretty cheap if you make it yourself - the biggest cost is the relays - but as you say, if you get them from the right place they can be pretty cheap. Then you need to take into account that a lot of owners probably won't want to venture behind the fusebox (the uprated loom is easy-ish to install without removing much), and still (at the moment at least) offers less of a voltage drop. You're right that the uprated loom isn't the most elegant solution, but it is the easiest and most effective.

 

That said, I think anyone going as close to OEM as possible might want a solution that doesn't involve chopping the headlight loom, so it could be perfect for them.

 

BTW, I don't think Climatronic uses relay 1 - the signal goes through the climatronic panel and the main Air Con current goes through the VR fan controller.

 

Love this sort of research though!

[davidwort 0]

that's interesting, and I'd say keeping relays inside the car is a much better option to under the bonnet, improving the voltage and adding higher output (new) bulbs will make a huge difference, does that mean you'll keep dim-dip too?

[J.C 10]

The only thing that I'd say is that a loom is pretty cheap if you make it yourself - the biggest cost is the relays - but as you say, if you get them from the right place they can be pretty cheap. Then you need to take into account that a lot of owners probably won't want to venture behind the fusebox (the uprated loom is easy-ish to install without removing much), and still (at the moment at least) offers less of a voltage drop. You're right that the uprated loom isn't the most elegant solution, but it is the easiest and most effective.

 

That said, I think anyone going as close to OEM as possible might want a solution that doesn't involve chopping the headlight loom, so it could be perfect for them.

 

BTW, I don't think Climatronic uses relay 1 - the signal goes through the climatronic panel and the main Air Con current goes through the VR fan controller.

 

Love this sort of research though!

 

Thanks for the reply,

I believe you are right about the air con relay, but just in case I thought I'd leave that alone, plus i'm pretty sure I'm not going to be in Australia driving my corrado in 40 degree heat thinking "geeez I wish I could wash my headlights":cool:

 

I have a bad habit of not thinking in layman or semi layman terms, to me a fuse box is just a box of electrical pathways to play with.

 

I wish I could sort out posting photos as it's not hard to do,

There is a possibility of a (nearly) plug and play loom, I've found every connector at the back of the fusebox EXCEPT "B" the one you use:bonk:

[J.C 10]

that's interesting, and I'd say keeping relays inside the car is a much better option to under the bonnet, improving the voltage and adding higher output (new) bulbs will make a huge difference, does that mean you'll keep dim-dip too?

 

Thanks for the reply,

It has made a difference even with original bulbs, On the way home from the school pickup I could see the reflection in other cars

Re. dim dip, Mine doesn't work at the moment as I've got the new headlight switch which doesn't have the required output which is on when side lights and ignition are on but off when ignition is off,

However I have simulated the output and YES, dim dip will work,

Upgraded headlight looms place their relay downstream of the point at which the feed from the dim dip resistor joins the dip beam circuit, this feeds voltage(reduced due to resistor) to the relay coil, causing the relay to energise,

This modification places the relay upstream of the dim dip resistor connection, meaning the dim dip resistor just feeds voltage to the secondary side of the relay contacts, therefore not effecting the relay (coil)

Edited September 19, 2013 by J.C