# Fog lights not working, could it be the switch?



## Garth (Feb 7, 2012)

As per title, my fog lights do not work. I have not tried replacing the bulbs yet as the green light on the switch doees no light up when the sitch is pulled out one click. The rear fogs work fine and the switch lights up red as it should when pulled out two clicks. The fuse is fine. Would the switch still light up greeen when the fogs are turned on and both bulbs have gone?

I have tried dismantling the switch and I can see the pins moving when the switch is turned or pulled for every function except the front fogs. I'm not sure which circuit is the fogs though so I'm not sure which pin is supposed to move.

Can anyone help out?

Thanks


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## Hoggy (May 8, 2002)

Hi Garth, Have you checked fuses, 3, 17, 18 & 36 all related to fogs.
Hoggy.


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## Garth (Feb 7, 2012)

Hoggy said:


> Hi Garth, Have you checked fuses, 3, 17, 18 & 36 all related to fogs.
> Hoggy.


Cheers Hoggy, fuses 3, 18 and 36 are fine but there is no fuse in 17 (no connections for it either) as it's listed as daylight headlights Canada.

Still no joy


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## Hoggy (May 8, 2002)

Hi Garth, "Bentley" states fuse 17 DRL & foglight relay, as no DRL for UK must just be for USA market then.
Hoggy.


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## j4zz_x (Jan 17, 2009)

Iam sure I read a guide on here recently on how to fix the switch, do a search (if it is that).


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## ScoTTish (Jun 26, 2008)

Better hope it is not the switch - cost me over £120 to replace when the switch stopped lighting up and it failed the MOT


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## 4ndrew (May 9, 2011)

Can get replacement used switches from eBay 4 circa £30. Not too expensive, ur best bet tbh tho, is just swap seiches with someone local, then you'll know straight away and be able to rule it out or get it sorted. ;-)


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## jamman (May 6, 2002)

This is a very different way of fault finding a bulb out :?

How about

a) Checking the bulbs and ruling that out first before dismantling any further

b) Fuses which you've done

c) Check it's getting +12v at the bulb connection

Then you know if it's a loom or switch fault


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## Garth (Feb 7, 2012)

jamman said:


> This is a very different way of fault finding a bulb out :?
> 
> How about
> 
> ...


Cheers mate. I don't know why I overlooked checking the voltage at the bulb. I'll give it a go tonight


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## Garth (Feb 7, 2012)

I know it's an old post and there's probably no-one interested, but I found the cause of the non-working fog lights...

I stripped the switch down to this:








You can see the second bar from the left has discoloured slightly. This had clearly had a short circuit or overload at some point. The plastic underneath had melted slightly and the contacts were burned. The two black plastic pins at the left of the photo push up the fog light contacts (left group, left one is rear foglight, right one is front foglight). One of the pins was slightly deformed so had to be reshaped and pushed back in. I cleaned the contacts and re-bent the front foglight one as it had warped due to heat. I tested the contacts with my multi-meter and once happy the switch was working as it should, I reassembled and put back in the car.

The fog lights now work again


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## ScottyRed (Jun 6, 2012)

Hi Garth, my TT has just failed its MOT on fog light failure, the switch fails to light front or rear lights, can you tell me how you managed to strip down the light switch?


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## Gazzer (Jun 12, 2010)

Garth said:


> I know it's an old post and there's probably no-one interested, but I found the cause of the non-working fog lights...
> 
> I stripped the switch down to this:
> 
> ...


hope you are not one of the nuggets that drive with front fogs on for no reason Garth?


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## Garth (Feb 7, 2012)

ScottyRed said:


> Hi Garth, my TT has just failed its MOT on fog light failure, the switch fails to light front or rear lights, can you tell me how you managed to strip down the light switch?


Once you remove the switch, it's pretty much push clipped together as I recall. It should be pretty self-explanatory once you see it. Just be gentle with it ;-)


Gazzer said:


> hope you are not one of the nuggets that drive with front fogs on for no reason Garth?


not me sir


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## Hacksawcats (Jan 16, 2020)

Does anyine know if there's a difference between a zenon and Halogen headlight switch with front & rear foglights? I've changed my Halogens to Zenons and now the front fogs dont work light up, the switch lights up, I've replaced the bulbs and checked the fuses.

Cheers


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## Hacksawcats (Jan 16, 2020)

Hacksawcats said:


> Does anyine know if there's a difference between a zenon and Halogen headlight switch with front & rear foglights? I've changed my Halogens to Zenons and now the front fogs dont work light up, the switch lights up, I've replaced the bulbs and checked the fuses.
> 
> Cheers


Just a quick update, so I've replaced the interior head/fog light switch with a xenon switch (no headlight adjustment wheel) now but that hasn't made a difference either, so I'm a bit lost! The only thing I can think of now is that the PIN outs different between xenons and halogens on the connectors to the headlights. Can anyone confirm this/had any experience of this?

Cheers


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## Hacksawcats (Jan 16, 2020)

Hacksawcats said:


> Hacksawcats said:
> 
> 
> > Does anyine know if there's a difference between a zenon and Halogen headlight switch with front & rear foglights? I've changed my Halogens to Zenons and now the front fogs dont work light up, the switch lights up, I've replaced the bulbs and checked the fuses.
> ...


Another update: Which has now left me totally confused! If I fit on halogen headlight and one xenon headlight both fog lights work!! Any help would be gratefully appreciated.


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## PlasticMac (Apr 25, 2017)

Disconnect one head lamp at a time, might give us a clue. Also, do the rear fogs work, on there own, and in the front and rear position?
Mac.


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## Hacksawcats (Jan 16, 2020)

PlasticMac said:


> Disconnect one head lamp at a time, might give us a clue. Also, do the rear fogs work, on there own, and in the front and rear position?
> Mac.


Hi Thanks for the reply. Both rear fog lights work with the new zenons. I will do as you have suggested and discomnect them one at a time, but do you mean one xenon and one Halogen? "Front & rear position" do you mean that the rears light up also one at a time?

Cheers


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## PlasticMac (Apr 25, 2017)

I have read it that with one halogen headlamp and on HID headlight fitted and working, both fog lights work,have I got that right? 
The fog bulbs (left and right) are separate from the main and dipped bulbs (left and right). So, unplug each headlamp bulb in turn, and note what the fogs do, plugging them in again, before moving to the next.

Edit:
The front fog bulbs (left and right) are separate from the main and dipped bulbs (left and right). So, unplug each headlamp bulb in turn, and note what each front fog does, plugging them in again, before moving to the next.

Let me know what happens. 
Mac.


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## David C (Apr 15, 2013)

Hacksawcats said:


> ...*Both *rear fog lights work with the new zenons.


There is only one rear fog light as std on the TT, on the driver's side.
The same position on the passenger side is the reversing light.


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## PlasticMac (Apr 25, 2017)

David C said:


> Hacksawcats said:
> 
> 
> > ...*Both *rear fog lights work with the new zenons.
> ...


Sorry, my mistake, trying to be precise, and failing!
Will edit. 
Mac.


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## Hacksawcats (Jan 16, 2020)

PlasticMac said:


> I have read it that with one halogen headlamp and on HID headlight fitted and working, both fog lights work,have I got that right?
> The fog bulbs (left and right) are separate from the main and dipped bulbs (left and right). So, unplug each headlamp bulb in turn, and note what the fogs do, plugging them in again, before moving to the next.
> 
> Edit:
> ...


Thanks Mac, I'll try your suggestion and get back to you. Sorry for the delay in replying.


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## Hacksawcats (Jan 16, 2020)

PlasticMac said:


> Disconnect one head lamp at a time, might give us a clue. Also, do the rear fogs work, on there own, and in the front and rear position?
> Mac.


Hi Mac,

Didn't read your previous posts properly, but I have disconnected the headlights on at a time and heres' my findings:

Rear Fog Works on all configurations.
Both Halogens plugged in: Both fog lights work.
One xenon plugged in: fog light not working
One Halogen plugged in: fog light works
One Halogen & one xenon plugged in: Both fog lights (zenon & halogen) work.

I'll do the bulb test tomorrow and get back to you.

Cheers

Cheers


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## davebowk (Aug 16, 2019)

You might have a short in one of your Xenons, see if the fogs work with each of the xenons with one halogen


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## PlasticMac (Apr 25, 2017)

Hacksawcats said:


> PlasticMac said:
> 
> 
> > Disconnect one head lamp at a time, might give us a clue. Also, do the rear fogs work, on there own, and in the front and rear position?
> ...


Good morning! With one xenon plugged in, and the fog light not working, does the xenon work?
Mac.


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## PlasticMac (Apr 25, 2017)

Another thought, check the front fog indicator (led) in the light switch. It should be ON when the fog is switched ON. If it is, even when the actual fogs are not, it proves the switch itself is working.
Mac.


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## Hacksawcats (Jan 16, 2020)

PlasticMac said:


> Hacksawcats said:
> 
> 
> > PlasticMac said:
> ...


Short Answer: yes.


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## Hacksawcats (Jan 16, 2020)

PlasticMac said:


> Another thought, check the front fog indicator (led) in the light switch. It should be ON when the fog is switched ON. If it is, even when the actual fogs are not, it proves the switch itself is working.
> Mac.


HI Mac, Yep, I've checked that the LED's have been checked and work and I did buy a replacement switch just in case, but made no difference.

Cheers


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## Hacksawcats (Jan 16, 2020)

davebowk said:


> You might have a short in one of your Xenons, see if the fogs work with each of the xenons with one halogen


mmm, you might be on to something there, because we (my son and I) did short out one of the lamps (cant remember if it was the xenon or the halagon, I think we shorted it out on on pins 1 & 4 and that made the fogs work, but it then seemed to cause the dipped beam not to work. So perhaps you could elaborate further (idiots guide) on " short one of my xenons", bearing in mind I haven't got a clue! Just one other thing to add to the mix that I forgot to mention: Is that I've fitted LED's to the lamps (except the actual zenons).

Many thanks


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## Hacksawcats (Jan 16, 2020)

PlasticMac said:


> Another thought, check the front fog indicator (led) in the light switch. It should be ON when the fog is switched ON. If it is, even when the actual fogs are not, it proves the switch itself is working.
> Mac.


HI Mac, still not done the bulb test yet, I got side tracked on to other jobs on the car. If you see my post back to Dave, you will see where I'm up to. I will do it tomorrow though and get back to you. But Daves thoughts about "shorting one of the headlights" seems to food for thought.

Cheers


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## davebowk (Aug 16, 2019)

Hacksawcats said:


> davebowk said:
> 
> 
> > You might have a short in one of your Xenons, see if the fogs work with each of the xenons with one halogen
> ...


It could be that the xenon ballast/controller is goosed.
The fogs will only work if the main beam is on (not sure if this is controlled by the switch or electronics), so if the xenon ballast/controller is faulty the car might not see that the main beam is on and so won't allow the fogs to work.
Just a wild guess as not sure how the light checking works. Are you getting any bulb out warnings on the DIS


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## Hacksawcats (Jan 16, 2020)

davebowk said:


> Hacksawcats said:
> 
> 
> > davebowk said:
> ...


Damm!, not checked that, I'll have look tomorrow. If the xenon ballast/controller is goosed, can it be repaired, replaced?


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## davebowk (Aug 16, 2019)

Sorry i meant low beam not main.
The ballast is the ally block on the side of the light unit, they can be replaced but make sure it is at fault as they are not cheap, swap to the other side to check.


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## PlasticMac (Apr 25, 2017)

My car is halogen, and the front fog lights can be switched on with side lights only, not conditional on head lights being on.
My feeling on this mystery is that it's an earth related fault, hence my suggestion to remove the bulb,while leaving the assembly in place. I'm guessing (I've not seen the xenon units) the xenons differ "mechanically" in someway to the halogens.
Mac.


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## davebowk (Aug 16, 2019)

I just checked as it was a while ago i changed mine.

My fog lights do work with the side lights but the ignition must be on.

I have all LED with the correct ballast resistors so no bulb warnings and no issues (as you mentioned fitting LED's earlier)

Do both xenons actually work as they should appart from the fogs not working?


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## PlasticMac (Apr 25, 2017)

Thinking a bit more, if, with ign and side lights on (no head/main/dipped), and xenons fitted, the fogs work, and don't in the same status with halogens, it is most likely that the problem is connection/earth related, as with side lights only on, there is no 12 volt connection to the head lights, only the earth. This check (sidelights only) is the same as my earlier bulbs out check, but, much easier!
Mac.


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## Hacksawcats (Jan 16, 2020)

Hi Guys,

Thanks for support so far. I've managed to take a good look at things and completed the bulb test. I think I've gone one step backwards! but hey ho:
xenon headlights fitted with all LED, except indicators & xenons:

First thing I noticed that the main beam LED on the dash is on permanently.

Second checked DIS and its reporting a bulb failure.... etc. only when xenons are switched on.

1. SIDE LIGHTS: Both side lights work in all configurations (1 in, 1 out etc.) but: Main beam on, on RHS lamp (LHS not on)

2. XENONS: Switched xenons on (dipped beam) and both work, along with side light., RHS main beam remains on but not LHS.

3. REAR FOG LIGHT: working ok in all configurations and LED on interior light switch work)

4.FRONT FOG LIGHTS: BOTH front fog lights now not working with LED's but LED on interior switch is illuminated. Both Fog lights do not work with Halogen bulb, either with one in and one out or both in etc. Also, do not work with one LED fitted and one Halogen (lol).

5.SIDE LIGHTS: LHS Removed, RHS working and vice versa (RHS Main beam still on)

6. MAIN BEAM: RHS main removed, LHS not on. LHS removed, RHS remains on.

7. MAIN BEAM: flashes on LHS, RHS doesn't when using off stick!

8. Ballasts swapped over but has made no difference.

I hope I've answered everyone's questions/suggestions, but if I haven't, feel free to point it out.

I think I've got my knickers in a twist now, so I think it's probably best I call in the professionals.

Cheers


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## PlasticMac (Apr 25, 2017)

Hi, can you clarify ".FRONT FOG LIGHTS: BOTH front fog lights now not working with LED's but LED on interior switch is illuminated. Both Fog lights do not work with Halogen bulb, either with one in and one out or both in etc. Also, do not work with one LED fitted and one Halogen"
Where are the LEDs fitted, in the front fogs?
I still think it's an earth problem, and the earth point common to the lamp circuits is under the battery. Check this carefully. It's not unknown for problems in that area. Good luck.
Mac.


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## Hacksawcats (Jan 16, 2020)

PlasticMac said:


> Hi, can you clarify ".FRONT FOG LIGHTS: BOTH front fog lights now not working with LED's but LED on interior switch is illuminated. Both Fog lights do not work with Halogen bulb, either with one in and one out or both in etc. Also, do not work with one LED fitted and one Halogen"
> Where are the LEDs fitted, in the front fogs?
> I still think it's an earth problem, and the earth point common to the lamp circuits is under the battery. Check this carefully. It's not unknown for problems in that area. Good luck.
> Mac.


Hi, 
Both front fog lights work with Halogen fog lamps and halogen bulbs. including one in one out.
Both front fog lights DO NOT work with Halogen fog lamps and LED's including one in and one out.
Both Fog lights worked using one Halogen fog light and one zenon fog light with LED bulbs.
I will check the earth under the battery and will report back.
Thanks


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## PlasticMac (Apr 25, 2017)

Hacksawcats said:


> PlasticMac said:
> 
> 
> > Hi, can you clarify ".FRONT FOG LIGHTS: BOTH front fog lights now not working with LED's but LED on interior switch is illuminated. Both Fog lights do not work with Halogen bulb, either with one in and one out or both in etc. Also, do not work with one LED fitted and one Halogen"
> ...


Hi, thanks for the update. Which position, side/main /dip are the LEDs in?
Mac,


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## Hacksawcats (Jan 16, 2020)

PlasticMac said:


> Hacksawcats said:
> 
> 
> > PlasticMac said:
> ...


"Which position"? I Have fitted LED's to the side lights, main beam and fog lights. The dipped beams are xenon.


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## brianmcc51 (Oct 4, 2014)

Could this be a polarity issue, can the fog light leds fit in the bulb holder either way. If so turn them round to change the polarity. I may be totally wrong here as some leds have polarity correction built in.


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## Hacksawcats (Jan 16, 2020)

brianmcc51 said:


> Could this be a polarity issue, can the fog light leds fit in the bulb holder either way. If so turn them round to change the polarity. I may be totally wrong here as some leds have polarity correction built in.


No they only fit one way. And as I mentioned early, they do work with Halogen head lights. thanks for the input anyway.
I've got an auto electrician booked for Wednesday now, so hopefully I can get it sorted.


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## PlasticMac (Apr 25, 2017)

I have LED front fogs (Night Eyes), and LED side lights. Main beam and dipped are halogen (Night Breaker and Phillips Racing). I have no problems whatsoever. My money is still on an earth issue. Let us know what the expert finds.
Mac.


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## Hacksawcats (Jan 16, 2020)

PlasticMac said:


> I have LED front fogs (Night Eyes), and LED side lights. Main beam and dipped are halogen (Night Breaker and Phillips Racing). I have no problems whatsoever. My money is still on an earth issue. Let us know what the expert finds.
> Mac.


Hi Mac, Sure thing, many thanks for all your support. It's just that I ended up just going round in circles!!


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## Hacksawcats (Jan 16, 2020)

Hacksawcats said:


> PlasticMac said:
> 
> 
> > I have LED front fogs (Night Eyes), and LED side lights. Main beam and dipped are halogen (Night Breaker and Phillips Racing). I have no problems whatsoever. My money is still on an earth issue. Let us know what the expert finds.
> ...


Cant wait to put the bumper back on, thats been sitting in the garage for weeks, while I've been trying to sort this blummin thing!!


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## Hacksawcats (Jan 16, 2020)

HI Guys, The sparks been and he reckons it's the Headlight Control Module that's been fried as his VAG-COM couldn't talk to it. Question is: Anyone know the location of it on a 2006 190 BVR Roadster? (He didn't know). The saga continues!

Many Thanks


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## Hacksawcats (Jan 16, 2020)

Hi Guys, Just thought I'd share with you where we're up to with lights situation LOL 

https://www.ttforum.co.uk/forum/viewtop ... 6&start=45


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