# Wiring Problem- Help Please



## teemyob (Nov 22, 2005)

Hello,

I am having to fit a Rear Fog lamp to a vehicle for a VOSA IVA Test.

Initially, I wired the relay into the live supply for the sidelights - that way the fog lamp would only come on when sidelights are switched on.

But VOSA state the Rear Fog lamp must only work with dipped headlights!.

So, I thought I would just connect the fog lamp relay to the dipped headlamp +Positive.

But I am having a brainstorm.

ALL Three pins to the headlamp bulbs are + Positive live with the headlamps off!

Can anyone shed any light (pardon the pun) on the matter for me please?

TM


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## cabby (May 14, 2005)

surely you will connect to the headlamp relay and put in a switch to control when you want the rear fog light on.as you will not want the lamp on all the time with dipped h/lights.

cabby


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## teemyob (Nov 22, 2005)

*relay*

Thanks Cabby,

I can't find the headlamp relay!

The car is Japanese and I can't find any wiring diagrams.

I have wired the rear fog via a relay and switch. I just need to find a wire that becomes live when the front headlamps are on.

But the 3 permanent live + Positives to the headlamp bulbs makes me think they could be neutrally switched?.

TM


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## philoaks (Sep 2, 2008)

If they were neutrally switched then that would explain the 3 lives. One would be live and the others would appear live but you would actually be measuring through the filaments.

If there are only 3 wires then there must be one permanent live that bridges to the high and low beam filaments. The other 2 would be a neutral switch for the high beam and a neutral switch for the low beam.

If you can identify what is what (should be easy to do if you remove the bulb first) then you could just put your relay between the permanent live and the low beam switched neutral (with a switch in line to control the fog light).

Hope that makes sense!


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## teemyob (Nov 22, 2005)

*lives*



philoaks said:


> If they were neutrally switched then that would explain the 3 lives. One would be live and the others would appear live but you would actually be measuring through the filaments.
> 
> If there are only 3 wires then there must be one permanent live that bridges to the high and low beam filaments. The other 2 would be a neutral switch for the high beam and a neutral switch for the low beam.
> 
> ...


I have disconnected the bulbs and the 3 pin connector has 3 permanent positive + (live at all 3 pins).


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## philoaks (Sep 2, 2008)

*Re: lives*



teemyob said:


> philoaks said:
> 
> 
> > If they were neutrally switched then that would explain the 3 lives. One would be live and the others would appear live but you would actually be measuring through the filaments.
> ...


Ah! How about with the bulb in and the headlights on. Do the readings make more sense then?


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## sallytrafic (Jan 17, 2006)

On both headlights?


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## teemyob (Nov 22, 2005)

*bulb in*

Not tried it with the bulb in!.

If they are neutral switched, would I be able to reverse the polarity on the relay?

TM


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## pete4x4 (Dec 20, 2006)

I think you need to check what the voltages are when the headlamp is switched on.
Modern cars tend to use electronic modules and the Canbus. Hopefully in your case the module isn't in the headlamp itself. I doubt there is a relay.
If your lucky one of those voltages will be different with the lamps on. Hopefully somewhere near 0v. You can then use that one to switch the relay.

Edit: Lol it's all in the timing, we are all saying the same thing.


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## sallytrafic (Jan 17, 2006)

Digital voltmeters have many traps for the unwary. Which is why people use a 12v filament lamp with cables and croc clips when tracing lamp wiring (also good for earth faults)


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## philoaks (Sep 2, 2008)

*Re: bulb in*



teemyob said:


> Not tried it with the bulb in!.
> 
> If they are neutral switched, would I be able to reverse the polarity on the relay?
> 
> TM


No problem there I wouldn't think. Normally one side of the relay coil is permanently earthed and the other goes to the switched live. In your case one side of the coil would be permanently live and the other to the switched neutral. End result would be the same, the relay would energise when the dipped headlights were on.


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## teemyob (Nov 22, 2005)

*module*



pete4x4 said:


> I think you need to check what the voltages are when the headlamp is switched on.
> Modern cars tend to use electronic modules and the Canbus. Hopefully in your case the module isn't in the headlamp itself. I doubt there is a relay.
> If your lucky one of those voltages will be different with the lamps on. Hopefully somewhere near 0v. You can then use that one to switch the relay.
> 
> Edit: Lol it's all in the timing, we are all saying the same thing.


There is no Module in the headlamp.
I cannot hear a Relay click when I switch the headlamps on.

Not sure about canbus on this model (2008 Honda Vamos)


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## kandsservices (Sep 5, 2010)

They are earth switched from memory its the top pin on the bulb but its been four years since i worked on a jap car so will stand corrected if you can take the feed of the headlight switch itself its a bit easier to wire up or even direct out of the fuse box.
Kev


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## teemyob (Nov 22, 2005)

*daylight*



kandsservices said:


> They are earth switched from memory its the top pin on the bulb but its been four years since i worked on a jap car so will stand corrected if you can take the feed of the headlight switch itself its a bit easier to wire up or even direct out of the fuse box.
> Kev


Thanks,

Now it is daylight I will go have a look and see if there is a way to connect to the stalk or fuse box (if I can find the fuse).

I can't get my head around reversing the polarity of the relay and switch.

Otherwise might be a yell.com for AE.
TM


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## MiketheWelshman (May 1, 2005)

Basically you will need to connect the relay across the headlight bulb, problem that will face you is having earth free coil connections, as a guide four pin relays are, but check carefully. Mike


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## teemyob (Nov 22, 2005)

*reverse*



MiketheWelshman said:


> Basically you will need to connect the relay across the headlight bulb, problem that will face you is having earth free coil connections, as a guide four pin relays are, but check carefully. Mike


Thanks Mike

I found This

My relay numbers are different.

So if I just swap my earth (negative - ) and Positive + on my relay, it should work okay?.

Yes K&S it is the top pin on the bulb. It is Positive until you switch the headlamps on and it then becomes negative - (earth).

TM


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## teemyob (Nov 22, 2005)

*coil*

I wired the coil of the relay to the headlamp dipped connections (85 & 86 on relay).

I now have a dim headlamp!

TM


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## pete4x4 (Dec 20, 2006)

So using Method 1 in your link describe what you did.
As a hint the negative side of the relay should have gone to whichever terminal went low on the head lamp. The positive side goes via a switch to your battery. The contacts of the relay are wired up normally one side to the battery via a fuse the other side to fog lamp.


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## teemyob (Nov 22, 2005)

*Wired*



pete4x4 said:


> So using Method 1 in your link describe what you did.
> As a hint the negative side of the relay should have gone to whichever terminal went low on the head lamp. The positive side goes via a switch to your battery. The contacts of the relay are wired up normally one side to the battery via a fuse the other side to fog lamp.


I wired the relay contacts across the two connectors for the main (dipped) Beam.

These pins are both live Positives +, until the headlamps are switched on. Then the top pin of the 3 becomes negative -

So I wired these (via an illuminated switch to the pins 85 & 86 of the relay. With number 30 being connected to a fused Positive from the battery and pin 87 to the lamp.

But it failed and now I have a dim headlamp. The Voltage measures 13 when not connected to the bulb. But shows 8 when the bulbs is in place.

TM


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## pete4x4 (Dec 20, 2006)

Not leaving you high and dry, just thinking!

You said three connections I assume the 3rd is for main beam and that still works ok?
Fuse still ok?
Does your relay have a diode across 85 & 86? Diode symbol on markings?


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## philoaks (Sep 2, 2008)

pete4x4 said:


> So using Method 1 in your link describe what you did.
> As a hint the negative side of the relay should have gone to whichever terminal went low on the head lamp. The positive side goes via a switch to your battery. The contacts of the relay are wired up normally one side to the battery via a fuse the other side to fog lamp.


I'd go with Pete's idea. Rather than using the headlight positive to power the relay coil, try bridging the fused live from terminal 30 to the positive side of the coil. Then you would only be using the switched negative of the dipped headlight to operate the relay.

I can't think of any reason why Plan A shouldn't have worked but then my knowledge of vehicle electrics is probably more suited to cars made before 1980!


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## pete4x4 (Dec 20, 2006)

I've looked at the circuit diagram for a late model honda Civic and it should work, the earth is indeed switched, each headlamp is fed from a fuse on the positive side, the negative sides are grounded via a relay controlled by the stalk


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## teemyob (Nov 22, 2005)

*Vosa*

Thanks for the replies Folks.

I don't have the Van here now, I ended up taking it to an Auto electrician as I don't have the time and the VOSA IVA test is Friday.

I managed to get the relay to operate from the headlamp but that is when the headlight went dim as I said. So put it back to sidelight operation and took it to the Garage.

Now they have it, they say they can wire it to dipped headlight operation but the rear Fog will go off if I use main beam or flash someone (this I knew).
(I also remember hiring a brand new car many years ago from Hertz, UK Spec. And that cars fogs went off when you used full beam).

The auto electrician asked me to clarify of this was okay with VOSA. The Auto Electrician also told me they had a Japanese import in the compound and that cars rear fog worked when only sidelights on/and or dipped beam.

Anyway, I rang VOSA and they failed to return my call re the main beam. Will have to call them again.

Thanks again.

TM


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## teemyob (Nov 22, 2005)

*Thought*

Just a thought.

Maybe I should have simply wired it direct, no relay via the dipped headlamps for the IVA Test

Then put it back to a relay and sidelight operation afterwards.

TM


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## teemyob (Nov 22, 2005)

*Thought*

Just a thought.

Maybe I should have simply wired it direct, no relay via the dipped headlamps for the IVA Test

Then put it back to a relay and sidelight operation afterwards.

TM


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## teemyob (Nov 22, 2005)

*VOSA*

UPDATE:

I phoned VOSA Twice this morning and finally spoke with someone who advised me that.

It is fine for the Rear Fog to work off Dipped beam and high beam (both) but does not matter if it goes out on high beam.

TM


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## teemyob (Nov 22, 2005)

*VOSA*

The Car failed its IVA Test see here

I rang the Auto electrician who did the wiring for me and he tells me he cannot wire the fog so it comes on with dipped beam and stays on with high.

Can anyone help please?

TM


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## pete4x4 (Dec 20, 2006)

Yep two diodes feeding the relay one from dipped one from main beam to the relay. Diode will prevent dipped from powering mainbeam and vice versa, Auto electrician should be able to sort that out. May have to go to Maplins for a 1N4004 or 1N4001 type 1A diode.

Pete


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## teemyob (Nov 22, 2005)

*tried*



pete4x4 said:


> Yep two diodes feeding the relay one from dipped one from main beam to the relay. Diode will prevent dipped from powering mainbeam and vice versa, Auto electrician should be able to sort that out. May have to go to Maplins for a 1N4004 or 1N4001 type 1A diode.
> 
> Pete


Thanks Pete, very much appreciated.

The Auto Electrician mentioned something about having tried diodes. But said it failed!

I will give him a call with this info.

TM


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## pete4x4 (Dec 20, 2006)

Probably had them round the wrong way as it's on the earth side so they would go the other way round to a +ve supply


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## teemyob (Nov 22, 2005)

*way around*



pete4x4 said:


> Probably had them round the wrong way as it's on the earth side so they would go the other way round to a +ve supply


So which way does the band on the diode go (think I have some in the Shed).

Would the band go nearest the bulb or furthest away?

TM


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## pete4x4 (Dec 20, 2006)

The band should go to the headlamp.
Relay should take about .5amp so make sure the diode can take that.


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## teemyob (Nov 22, 2005)

*diodes*



pete4x4 said:


> Yep two diodes feeding the relay one from dipped one from main beam to the relay. Diode will prevent dipped from powering mainbeam and vice versa, Auto electrician should be able to sort that out. May have to go to Maplins for a 1N4004 or 1N4001 type 1A diode.
> 
> Pete


I found 50 1n5408 diodes in the garage but no 1n4001/4's

Typical


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## pete4x4 (Dec 20, 2006)

They'll do!! 1N5408 is a 3A diode....


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## fdhadi (May 9, 2005)

Hi Tm,

My 58reg Ford Fiesta rear fog lights work with just the side lights on, ie: no need for headlamps to be switched on. My motorhome (Fiat) fog lights only work when the head lights are switched on. 

Is there a rule for cars and a rule for vans?


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## teemyob (Nov 22, 2005)

*Diodes*



pete4x4 said:


> They'll do!! 1N5408 is a 3A diode....


Never Mind.

Mrs TM nipped down to Maplins, it is only a mile from us.

I soldered them into the loom and heat shrunk wrapped into a "Y" and guess what!?

The Rear Fog works on Dipped and Main beam with no effect on the headlamp ops.

Thanks everyone and a very special big thanks Pete4X4.

TM


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## teemyob (Nov 22, 2005)

*When I get time*



fdhadi said:


> Hi Tm,
> 
> My 58reg Ford Fiesta rear fog lights work with just the side lights on, ie: no need for headlamps to be switched on. My motorhome (Fiat) fog lights only work when the head lights are switched on.
> 
> Is there a rule for cars and a rule for vans?


I will explain and give the Info when VOSA pass my car


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## fdhadi (May 9, 2005)

:wink:


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## teemyob (Nov 22, 2005)

*off and on*

With 1 slight problem!

If you have no lights on at all
The fog is switched on (but not working as no power from headlights)

If you flash high beam......

The rear Fog Flashes too!

BUT

There is no sequence for this in the VOSA bible

This is the Draft - but my VOSA 26/07/2010 copy is the same

So Can it Fail?

TM


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## pete4x4 (Dec 20, 2006)

Hmmm, you'll never stop that happening, that's why there is a warning light for the fog lamp I would suggest, so that you can turn it off in those circumstances.

That would be a bit harsh to fail it on that.


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## pete4x4 (Dec 20, 2006)

You could take the 12 volt feed for the relay coil from the sidelights.
That way the VOSA table can be met ie the fog lamp would still flash with mainbeam but only if the sidelights are on.

What I don't know is are your sidelights wired the same way as your headlamps ie switched earth. If that's the case then it won't work and you would have to use a second relay whose coil is connected to the sidelights and whose contacts switch the 12volts for the first relay connected to the fog lamp.
If you follow!


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## teemyob (Nov 22, 2005)

*Follow*



pete4x4 said:


> You could take the 12 volt feed for the relay coil from the sidelights.
> That way the VOSA table can be met ie the fog lamp would still flash with mainbeam but only if the sidelights are on.
> 
> What I don't know is are your sidelights wired the same way as your headlamps ie switched earth. If that's the case then it won't work and you would have to use a second relay whose coil is connected to the sidelights and whose contacts switch the 12volts for the first relay connected to the fog lamp.
> If you follow!


Thanks Pete.

I think I follow.

Not sure what the Auto Electrician did. all I can see is that he added a second relay to the side of mine. I have not followed or tried to trace the wiring. I simply put the Diodes in as you said and it worked.

The side lights are simple + & - This is the way I originally wired them taking the switched +Positive to the relay.

So I think I understand what you are now saying, I will just have to work out what wire from the relay terminal I have to connect to the switched + on the sidelights.

Thanks
TM


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