Me and another FOC user are trying to make our sidelights come on when unlocking the car, like the fiesta does.

We have tried connecting the footwell lights to the sidelights in the fuse box:

• C102 position 35 (Footwell lamps)
• C96 position 28 (Front Right Park)

However when we do so all four park lights come on, two front and two rear, however they stay on until the cable is disconnected when we wanted them to go off and on with the courtesy footwell lights.

There is no voltage on C102 position 35 (Footwell lamps) unless the footwell lights are on.

Does anyone have any suggestions to what we are doing wrong and why all four park lights stay on even when the footwell lights have gone out?

 

To be honest its nothing short of a miracle that you haven't damaged the BCM linking the two circuits directly together.

If you want to do this, then you need to use a relay. Connect the footwell lamps to the coil of the relay. Then go to the switch for the sidelights and connect the relay contacts in parallel with the sidelight circuit.

When the footwell lights come on the relay will turn on and close the contacts which will be like turning the sidelight switch on.

Just out of interest have you checked with FORScan that there's not a setting to enable the sidelights during unlock ?

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Just out of interest have you checked with FORScan that there's not a setting to enable the sidelights during unlock ?

Unfortunately there isn't something with Forscan or even UCDS. It's annoying because the puddle lights, courtesy light (auto mode) and footwell lamps all work precicely how you'd want them.

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To be honest its nothing short of a miracle that you haven't damaged the BCM linking the two circuits directly together.

Looking at the wiring schematics (page 63 Head Lighting - Autolamps), there isn't anything in particular inside the PJB or elswhere. The wire goes straight from the switch, through PJB (to add fuses) and then to the lights. It doesn't go through the CAN so i wouldn't expect to fry anything, because it looks like an electrical circuit rather than electronic, but i might be wrong.

As both cars have autolamps, i wonder if the problem is with the autolamp relay getting triggered somehow...

It very much depends on if this is a Fiesta or a Focus and what age they are.

Most lighting functions, especially those with Auto lights don't use relays instead the function is controlled by the Body Control Module which in the case of the fiesta and focus is part of the fusebox located on the passenger side behind the glovebox.

Functions such as the timing of the footwell lights/puddle lights etc. is a function of the BCM. Older models do have in some cases relays for the headlights but that is not common now. The Canbus control is used to communicate between modules like the ECU,BCM,DDM,PDM,APIM etc. but the actual switching of a circuit is done by the respectful module. With this in mind control of say the footwell lights is switched by a power MOSFET located inside of the BCM. It takes very little current to turn the MOSFET on and if you link circuits then it would be very possible that once turned on it would be able to draw enough current from the joined circuit that would then keep it in the on state.

 

 

10 minutes ago, unofix said:

It very much depends on if this is a Fiesta or a Focus and what age they are.

Most lighting functions, especially those with Auto lights don't use relays instead the function is controlled by the Body Control Module which in the case of the fiesta and focus is part of the fusebox located on the passenger side behind the glovebox.

Functions such as the timing of the footwell lights/puddle lights etc. is a function of the BCM. Older models do have in some cases relays for the headlights but that is not common now. The Canbus control is used to communicate between modules like the ECU,BCM,DDM,PDM,APIM etc. but the actual switching of a circuit is done by the respectful module. With this in mind control of say the footwell lights is switched by a power MOSFET located inside of the BCM. It takes very little current to turn the MOSFET on and if you link circuits then it would be very possible that once turned on it would be able to draw enough current from the joined circuit that would then keep it in the on state.

 

 

Both cars are a Focus (Mine is a 2010)

What you describe in your comment is what appears to be happening in reverse, the sidelights stay on even after the footwell lights go off.

We are thinking of using a diode to block the current from travelling backwards and to only allow current to travel from the footwells lighting cable once a specific voltage is reached i.e. 5v

I was looking into a Zener Diode with a breakdown voltage of around 5v which would mean the diode would not let voltage through until the voltage exceeds 5v?

First point I would say is if you take the sidelight circuit of 4 x 5W lamps plus number plate lamps, plus instrument panel lights and any thing else that I've forgotten you are going to need a diode of at least 30 Watts.

Next I'm half understanding your idea of using a diode, but why would you use a Zener diode ? You want it to fully block all reverse current so a normal power diode would be what is needed. I still think the safest and simplest way is to use a relay which will provide total isolation between circuits.

4 minutes ago, unofix said:

First point I would say is if you take the sidelight circuit of 4 x 5W lamps plus number plate lamps, plus instrument panel lights and any thing else that I've forgotten you are going to need a diode of at least 30 Watts.

Next I'm half understanding your idea of using a diode, but why would you use a Zener diode ? You want it to fully block all reverse current so a normal power diode would be what is needed. I still think the safest and simplest way is to use a relay which will provide total isolation between circuits.

The Zener Diode was my idea because of the the breakdown voltage, wanted to make sure it would only allow current through once a certain voltage is reached i.e. 5v

When giwrgos_ath tested for voltage he got 0.1v from the footwell lighting cable, I thought maybe this was enough of a signal to make the car think that the cars lights had been set to parking and could have been the reason why all sidelights stayed on even though the footwell lights had gone off. So the idea of a Zener Diode came from that as it would not allow any voltage through until 5v had been exceeded. Hope that makes sense?

Any ideas on the kind of relay we would need?

17 minutes ago, unofix said:

I still think the safest and simplest way is to use a relay which will provide total isolation between circuits.

Would one of these be suitable?

https://tinyurl.com/mryhhmze

Hello Steve, putting it politely the zener diode is shall we say not the way to go. All diodes have a 0.6V drop across them anyhow and so the 0.1V you measured would not be conducted by a diode. You can't just stick a 5V zener diode in series with the supply, it will get stupidly hot and eventually fail. You need to build a switching circuit, and use zener to sense the voltage and turn on a transistor to carry the load current. 

6 minutes ago, stevejwalford said:

Would one of these be suitable?

Yes they would do 👍

7 minutes ago, unofix said:

Yes they would do 👍

Is this how you would wire it up?

I always wanted this when I had a MK2 as well cos guys at my work had fiesta's that would do it and it would make me jealous and I couldn't find out how to do it. Good luck I hope you manage it.

Hello Steve,

First point the relay terminal 85 is Ground (Negative) and terminal 86 should be connected to the positive side of the Footwell lights.

Terminal 87 (Normally Open) is correct, connect that to the sidelight circuit.

Terminal 87a (Normally Closed) is not used and should be left un-connected

Terminal 30 (Common) - your idea of connecting it to a positive supply via a fuse would work, BUT, I would be unhappy doing that as you are introducing a new supply that is technically not fully controlled.  The way I think would be a better way would be to find the live feed to the existing sidelight switch and use that.

All that said apart from 85 and 86 being crossed and my preference to for using the sidelights normal feed  - it should work !!!

I have to throw in a disclaimer at this point and say you do this at your own risk, and I'm not responsible if damage is caused or it just doesn't work.

Thanks @unofix, think you've helped getting us unstuck!

Wouldn't it be best to get the 4-pin version instead?

Also, i'm thinking of tapping to the cable that runs from the lights switch to the PJC (C102 1 OG/YE) so whatever current we introduce will need to go through the two 7.5A fuses (F124 & F125) before reaching the parking lights. Do you see anything wrong with this?

Also, if i'm not mistaken, the dash and the plate lights don't come on in position P or Auto and only light on 1 and 2 but that shouldn't affect this mod.

Terminal 85 is Ground. There is a back EMF diode inside the relay, if you connect the coil connections backwards you will cause a short-circuit.

It makes no difference using the a 4 pin or 5 pin. I would probably use the 5 pin version, you just never know when you might find a use for the normally closed contact..

The supply from/to the light switch  (C102 1 OG/YE) should be OK.

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Terminal 85 is Ground. There is a back EMF diode inside the relay, if you connect the coil connections backwards you will cause a short-circuit.

Not sure why they show it the other way on the drawings, but i wouldn't really trust the random seller on Amazon... Thanks for pointing this out!

Maybe we should consider a pre-fused one like this https://www.amazon.co.uk/MinticeTM-Vehicle-Motor-Heavy-Socket/dp/B01FSB73P0/ ? Probably also change the fuse to a 15A

That looks quite a decent relay. The sidelights should take less than 7.5A so I would stick to using that size fuse. Worst case if it does take a little more you can always replace the fuse with a 10A

So I gave this a go this morning, but unfortunately It didn't work...

Wired them as following

• 30 (red) -> Permanent live that i got from C102 23 OG-YE which is the power to the cigar lighter
• 85 (black) -> Ground point on the sill of the door, under the plastic trim
• 86 (white) -> Switched live from footwell lamps
• 87 (blue) -> To parking lamps C102 1 OG-YE which is the wire running between the switch and the PJB (then travels through F124 & F125 to the lights)

For some reason, the lights remained on after locking the car. Am i doing something wrong?

Good morning George if you connected it as above and your sidelights remained on, then the only explanation that there can be is that the relay coil remained energized. Meaning that the footwell lamps must have remained on.

I've just had an idea !!!!!!!!!!!!!!!

We are assuming that the footwell lamps are turned on and off by a positive supply. It could be that the positive supply to the footwell lamps is always live and that it is the negative of the lamp that is being switched.

Simple test to do first. When the sidelights are on, disconnect the wire from relay terminal 86 and see if the lights go out. let me know what happens.

Hi, not sure if you have access to the schematics? They can be found here https://www.fordownersclub.com/applications/core/interface/file/attachment.php?id=42087 (https://www.fordownersclub.com/forums/topic/42898-ford-focus-full-wiring-schematics-mk225-and-mk3/?_rid=29590)

On page 72 there's the Courtesy lighting diagram and that shows the footwell wiring starting (C102 35) and finishing (c102 41) inside the PJB unlike other lights that terminate at a ground point. They also go through the battery saver relay and the CAN.

Annoyingly, the footwells go completely off and you can tell because they are LEDs and there's not even a glimpse of light.

Also, page 63 on that PDF has the Head Lighting - Autolamps and that shows the entire path and all connections happening to the current as it runs from C102 1.

I'm at a complete loss here, but i think the Autolamp relay might have something to do with this because if you follow the wires towards the battery, if the switch is in the Auto position, the current can bypass the relay and possibly keep it energised?

 

2 hours ago, giwrgos_ath said:

• 30 (red) -> Permanent live that i got from C102 23 OG-YE which is the power to the cigar lighter
• 85 (black) -> Ground point on the sill of the door, under the plastic trim
• 86 (white) -> Switched live from footwell lamps
• 87 (blue) -> To parking lamps C102 1 OG-YE which is the wire running between the switch and the PJB (then travels through F124 & F125 to the lights)

If what you said appears to be true would the fix to this be the following:

• 30 (red) -> Switched negative from footwell lamps
• 85 (black) -> Ground point on the sill of the door, under the plastic trim
• 86 (white) -> Permanent live that i got from C102 23 OG-YE which is the power to the cigar lighter
• 87 (blue) -> To parking lamps C102 1 OG-YE which is the wire running between the switch and the PJB (then travels through F124 & F125 to the lights)

4 minutes ago, stevejwalford said:

If what you said appears to be true would the fix to this be the following:

• 30 (red) -> Switched negative from footwell lamps
• 85 (black) -> Ground point on the sill of the door, under the plastic trim
• 86 (white) -> Permanent live that i got from C102 23 OG-YE which is the power to the cigar lighter
• 87 (blue) -> To parking lamps C102 1 OG-YE which is the wire running between the switch and the PJB (then travels through F124 & F125 to the lights)

so toggle 30 with 86? shouldn't 30 be a permanent live tho?

I believe a relay should work both ways? I would wait for unofix to confirm though...

 

Sorry it should be 85 and 86 that are changed I believe:

• 30 (red) -> Permanent live that i got from C102 23 OG-YE which is the power to the cigar lighter
• 85 (black) -> Switched negative from footwell lamps
• 86 (white) -> Positive from footwell lamps
• 87 (blue) -> To parking lamps C102 1 OG-YE which is the wire running between the switch and the PJB (then travels through F124 & F125 to the lights)

I am not 100% sure on this so just wait for unofix...