Well... a potential mod...

 

I was changing a rear light bulb today when I noticed that the rear sidelight bulbs are twin filament, where the more powerful (brake) filament is never utilised.

I tried, and I proved, that it is possible to activate this filament (so on braking the top and the bottom brake lights would illuminate - more safety?) by bridging the green/red wire and the grey/white wire.

 

Anyone done this, any potential drawbacks, or legality issues?  Is it even legal to have two brake bulbs per rear corner??

Don't know how the bulb failure warning system might react with the additional current draw (I can only assume it will not detect one out of 4 failing, or even 2 out of 4 failing)...

 

I must say at this point I reverted back to standard, I don't know the fuse ratings, etc, I have not looked into any of this, but seems plausible to me as a "potential almost pointless mod just for the sake of modding  "

 

 

Is it a twin filament bulb as it's also the rear fog light.

It is the fog light, it's only wired on one side, and although the bulb is the same on the other, isn't connected.

 

I have run a connecting wire on my car from the offside fog wire and connected into the connector plug for the passenger and so now have both fog lights working.

It is the fog light, it's only wired on one side, and although the bulb is the same on the other, isn't connected.

 

I have run a connecting wire on my car from the offside fog wire and connected into the connector plug for the passenger and so now have both fog lights working.

 

I was wondering if my car was broken but handy to know that it's normal for the fog light to only illuminate on one side (driver's side)!

 

Edit: Just noticed this is on a Superb - can anyone confirm that the mk1 Octy rear fog light is only supposed to illuminate on the driver's side - even though the passenger side has a twin filament bulb?

Oh yes, forgot about the Fog light!

Doh.

Isn't left v right foglight illumination what comes out of territorial coding in VCDS? i.e. Right for RHD and left for LHD traffic?

Why forget about it, when you can isolate both fogs fully with Schottky diodes (4 in total, 2 to each lamp), run a single wire from the active fog, and run both as twin fogs + additional brake lights (feeding each Schottky with either brake or fog signal for this side).

 

That is what I have on my cars (first on Octy, now on Superb and on Roomster). Although the bottom lamps on my cars are actually LEDs, makes for faster brake lights (you can see them lighting up first), and the red LEDs last forever, or in my case 7 years/110k miles so far. Twin fogs are a must if you drive abroad IMHO.

 

You cannot do anything on VCDS other than disable monitoring, as there is physically a cable missing to the other fog. Since fogs are not monitored anyway, and I sometimes drive in -15degC and below,  I preferred to keep monitoring and install load resistors, glued to bottom of each rear lamp's metal carrier, largely prevents frost on the inside of each cluster in winter.

Edited 18 December, 201411 yr by dieselV6

Hmm....

I sense another Xmas break time project...

I think the single fog light is a German idea so that people are less likely to mistake twin fog lights for brake lights (this was before third high level central brake lights were invented)