Rear Lights - Fog Light Modification

[Nic]

Is there a how to guide that explains how to modify the standard rear lights to include the rear fog light?

[CalMac]

I'm interested too. Something I've been meaning to do for ages but never got around to looking into

[craig]

I believe there is a guide on the oc in 'know your 2' to do it with diodes.

[Pauln]

Here you go

link for how to guide

Make sure you fit the diodes the correct way around as these "one way" devices are needed to keep the brake light power feed isolated from the fog light power feed

Paul

[Shaoxter]

Until now I never gave any thought to what the rear lights were doing... but this quad light mod looks awesome!!

Shame I suck at electrical stuff though...

[Nic]

Here you go

link for how to guide

Make sure you fit the diodes the correct way around as these "one way" devices are needed to keep the brake light power feed isolated from the fog light power feed

Paul

Thanks Paul

[tiff_lee]

As above until I read this thread I never even gave the rear lights a thought, thanks for the link another job on the to do list............

[Martin F]

Or you could just use one of the reversing lights, that way you could still have four tail lights and four brake lights, looks well better Imo

[Pauln]

Or you could just use one of the reversing lights, that way you could still have four tail lights and four brake lights, looks well better Imo

But other than when you switch on your rear fog lights, that's exactly what you can have with this "diode" mod four brake lights and four tail lights.

Paul

[craig]

Or you could just use one of the reversing lights, that way you could still have four tail lights and four brake lights, looks well better Imo

But then it looks like you've a blown reverse light bulb.

My car failed the mot a few years ago doing this as it was just a pale pink glow

Diodes or relays ftw

[Martin F]

Or you could just use one of the reversing lights, that way you could still have four tail lights and four brake lights, looks well better Imo

But then it looks like you've a blown reverse light bulb.

My car failed the mot a few years ago doing this as it was just a pale pink glow

Diodes or relays ftw

Mine past mot with this mod And as the chances of me ever having to actually drive in fog are next to zero it is best for me, saying that I don't mind having a normal one under the bumper, just hang it up so it is out the way until either mot time or when you actually need it

The four and four are worth these hassles, are they not ?

[CalMac]

According to that guide the two inner lights are already wired up as rear fogs. Why don't mine work as fogs then?! Mine's had one of the standard aftermarket foglights cable-tied on the rear exhaust grille - why would the importer bother doing that if it supposedly already has rear fogs wired up?

I like the idea of having all four lights as driving/braking lights though

[craig]

Imports don't have rear fog lights, hence the additional one that some bolt to the grill.

Agreed, Gotta have four and four. There's just better ways than converting a reverse light.

My set up has four tail, four brake lights, and inners as fog lights, complete with illuminated us red triangles. I have relays wired in that disengage the inner lights as brake lights when the fog lights are in use.

In addition, I have 2 reverse lights

[Martin F]

Agreed, Gotta have four and four. There's just better ways than converting a reverse light.

You are so right looking at it that way, it looks ridiculous and is very impractical, I just have it because that is the way it was when I bought the car

[Pauln]

(post updated to correct errors)
As has been said, that guide is based on the assumption that the inner pair of lights is already fitted with a dual filament lamp, so all four lamps act as tail/brake.

But what is actually fitted to your car will depend on the model and whether it has been modified over the years. Whilst up to rev 2 models both the inner and outer lights were fitted with dual filament lamps, rev 3+ have dual filament lamps in the outer pair, and single filament lamps fitted in the inner pair.

Rev 3+ UK models also have a different reflector in the inner pair (sometimes called a half moon reflector). This doesn't fill the entire lamp housing, so it's easy to see which you have. The JDM models have a full size reflector.

If you already have dual filament lamps in the inner pair, you just need diodes (or a relay if you prefer) to make the inner pair rear, brake and fog. If you only have single filament lamps in the inner pair, you also need to change the lamp holders for the dual filament type (3 wire).

Personally I much prefer to have two reversing lights, the streets around our way are badly lit at it is and parking spaces are at a premium.

If your fitting rev 3 lights to a rev 1/2, you also need to be aware that the connectors at the end of the wiring loom on rev 2 lights are different to those fitted to rev 3. So you either need to swap connectors where the lights connect to the main loom, or re-use the looms from your rev 2 lights. Just to add to your troubles the lamp holders on a rev 2 use a different lug layout to those on rev 3+, but can be made to fit.

Personally I opted for re-using my rev 2 loom and the careful use of a Stanley knife to ensure the rev2 holders were a good fit in the rev 3 lights and locked firmly into place.

As the original guide I linked to no longer seems to be available, I've included an updated version of the wiring diagram that was included in that guide in case it helps others.



Paul

[JohnnyC]

I had mine set up with dual filament bulbs like:
tail lights - all four came on (dim)
brake lights - all four came on (bright)
fog lights - inner lights came on (bright) (and outer lights were also on dim, as foglights can only work when when headlights on)

Obviously if you braked while foglights on then it just looked like the outers did anything.

And I had a switch that disabled the inners being on for both tail and brake lights, but kept them for foglights - just as per original UK spec

[Willenium]

As Red said, that guide is based on the UK model which only uses a single element bulb in the inner pair as a fog light. The UK model also has a different reflector in the inner pair (sometimes called a half moon reflector). This doesn't fill the entire lamp housing, so it's easy to see which you have. The JDM models have twin filament lamps in the inner, so you have 4 rear lights and 4 brake lights.

If you already have JDM rear lights, you just need diodes (or a relay if you prefer) to make the inner pair rear, brake and fog. If you have UK rear lights you also need to change the lamp holders on the inner pair.

Personally I much prefer to have two reversing lights, the streets around our way are badly lit at it is and parking spaces are at a premium.

Paul

Mine didn't. Still had single filament on the inners which came on as brake as opposed to fog. In theory you could chop the fog feed off a UK one and splice that bulb holder into the brake so it'll come on as a standard JDM setup or wire in holders for dual filament bulbs and do the quad light mod

[parker455]

As Red said, that guide is based on the UK model which only uses a single element bulb in the inner pair as a fog light. The UK model also has a different reflector in the inner pair (sometimes called a half moon reflector). This doesn't fill the entire lamp housing, so it's easy to see which you have. The JDM models have twin filament lamps in the inner, so you have 4 rear lights and 4 brake lights.

If you already have JDM rear lights, you just need diodes (or a relay if you prefer) to make the inner pair rear, brake and fog. If you have UK rear lights you also need to change the lamp holders on the inner pair.

Personally I much prefer to have two reversing lights, the streets around our way are badly lit at it is and parking spaces are at a premium.

Paul

Glad I read this otherwise I'd have bought bulb holders too! Result!