Adding fog lights and unable to find the correct fuse

[jsean]

I added fog lights to my stripper version ‘08 Ford Focus using a generic wiring harness off Amazon. Hot is wired into the battery and because the ground cable is comically short I tied that into one of the grounds that’s on the driver’s side fender.

On the inside, I have the ground attached to the grounding location inside the drivers’s side lock panel. For the hot wire inside the cabin, I used one of the Bussman add a fuses. The fog lights power on which is fine and dandy.

However, I can’t seem to find a fuse slot in the fuse box that’s underneath the dash. I’ve tried about 8 different slots and they all seem to power the fog lights without ignition on.

What I’m trying to find is a circuit in the under dash fuse panel that will only be powered with key on.

Fuse list is here for reference: Focus fuses

Anyone here have recommendations on how to proceed? I’ve tried the subwoofer, heated seats, satellite radio, instrument panel backlighting, and ABS slots - no difference. The newly added fog light switch is constantly powered on (can click it on/off to get the lights on) and doesn’t lose power when the BCM cuts power to the dome lights after 10 mins of inactivity.

 

[Leo99]

If it makes you feel any better, I added a dash cam to my Camry and it took me a long time to find a fuse that was only hot when the ignition was on. Just like your car, none of it made sense.

 

[Nukeman7]

Have you tried testing the power slot on fuse #21? It is specifically designated for the fog lights.

 

[vavavroom]

I added fog lights to my stripper version ‘08 Ford Focus using a generic wiring harness off Amazon. Hot is wired into the battery and because the ground cable is comically short I tied that into one of the grounds that’s on the driver’s side fender.

On the inside, I have the ground attached to the grounding location inside the drivers’s side lock panel. For the hot wire inside the cabin, I used one of the Bussman add a fuses. The fog lights power on which is fine and dandy.

However, I can’t seem to find a fuse slot in the fuse box that’s underneath the dash. I’ve tried about 8 different slots and they all seem to power the fog lights without ignition on.

What I’m trying to find is a circuit in the under dash fuse panel that will only be powered with key on.

Fuse list is here for reference: Focus fuses

Anyone here have recommendations on how to proceed? I’ve tried the subwoofer, heated seats, satellite radio, instrument panel backlighting, and ABS slots - no difference. The newly added fog light switch is constantly powered on (can click it on/off to get the lights on) and doesn’t lose power when the BCM cuts power to the dome lights after 10 mins of inactivity.

I would not wire fog lights without using a relay. Finding ground, 12V, switched 12V etc terminal posts under the dash used to be easy. Many newer cars run much of the wiring through a computerized module. Fuse boxes are also no longer as easily accessible as they once were. At least its difficult to add a circuit. You may be able to piggyback of an existing fuse with a fuse splitter. Hopefully the fuse box cover will still fit. I bet you got two fuse boxes.

 

[jsean]

If it makes you feel any better, I added a dash cam to my Camry and it took me a long time to find a fuse that was only hot when the ignition was on. Just like your car, none of it made sense.

This is what I’m worried about. Having to trial and error my way through the whole fuse box. Did you have to constantly disconnect the negative terminal at the battery each time you checked a new fuse slot?

 

[jsean]

Have you tried testing the power slot on fuse #21? It is specifically designated for the fog lights.

Tried that one a few minutes ago. Did the same thing! I don’t understand how several of these fuse slots are just constant power.

 

[Leo99]

This is what I’m worried about. Having to trial and error my way through the whole fuse box. Did you have to constantly disconnect the negative terminal at the battery each time you checked a new fuse slot?

I did not even think to disconnect the battery.

 

[jsean]

I would not wire fog lights without using a relay. Finding ground, 12V, switched 12V etc terminal posts under the dash used to be easy. Many newer cars run much of the wiring through a computerized module. Fuse boxes are also no longer as easily accessible as they once were. At least it’s difficult to add a circuit. You may be able to piggyback of an existing fuse with a fuse splitter. Hopefully the fuse box cover will still fit. I bet you got two fuse boxes.

No kidding. I spent several minutes trying to contort my hand under the dash panel to get to the fuses. Couldn’t get to them, figured I give YouTube a shot. Sure enough - apparently you just yank off the entire under dash panel to gain access to the fuse box. Surprisingly, it’s held in place with just press clips.

The wiring harness I got does have a relay and a fuse on the hot wire on the engine bay side. So I feel ok with that, it’s just the lack of finding a usable switched fuse slot has me stumped.

 

[jsean]

I did not even think to disconnect the battery.

Oh ok and I assume you didn’t notice any issues? That should make it much faster for me. I’ve been disconnecting/reconnecting the negative cable and it’s starting to get annoying doing it several times…

 

[vavavroom]

No kidding. I spent several minutes trying to contort my hand under the dash panel to get to the fuses. Couldn’t get to them, figured I give YouTube a shot. Sure enough - apparently you just yank off the entire under dash panel to gain access to the fuse box. Surprisingly, it’s held in place with just press clips.

The wiring harness I got does have a relay and a fuse on the hot wire on the engine bay side. So I feel ok with that, it’s just the lack of finding a usable switched fuse slot has me stumped.

Find the terminal block. You may have to remove the fuse box. I just don't know your Focus. The only thing I ever did on a Focus was remove tail light to replace a bulb.

 

[eljefino]

The fuse boxes aren't for your convenience, they're for Ford's.

The way this car is laid out, your accessories run off the in-cabin fusebox while the ignition switch output basically returns to the under hood box. If you want a switched source, look there. Like others said, add a relay and things get better. I assume the ground in the passenger compartment is for the little light in the switch and for nothing else.

I'd tap the breaker for the sunroof and power windows. You get the added advantage of it being a self-resetting breaker if you do too much at one time.

 

[Trav]

I added fog lights to my stripper version ‘08 Ford Focus using a generic wiring harness off Amazon. Hot is wired into the battery and because the ground cable is comically short I tied that into one of the grounds that’s on the driver’s side fender.

On the inside, I have the ground attached to the grounding location inside the drivers’s side lock panel. For the hot wire inside the cabin, I used one of the Bussman add a fuses. The fog lights power on which is fine and dandy.

However, I can’t seem to find a fuse slot in the fuse box that’s underneath the dash. I’ve tried about 8 different slots and they all seem to power the fog lights without ignition on.

What I’m trying to find is a circuit in the under dash fuse panel that will only be powered with key on.

Fuse list is here for reference: Focus fuses

Anyone here have recommendations on how to proceed? I’ve tried the subwoofer, heated seats, satellite radio, instrument panel backlighting, and ABS slots - no difference. The newly added fog light switch is constantly powered on (can click it on/off to get the lights on) and doesn’t lose power when the BCM cuts power to the dome lights after 10 mins of inactivity.

Have you looked for OE wiring for them that may be tied or taped up close to the lights location. Does it have a location for the fog light switch in the dash? There may be wiring already there for them.

 

[Cujet]

Consider wiring the fogs to come on with the parking lights. "IF" they are not also used as turn signals.

It eliminates running wires into the cabin and they remain on with Low or High beams on. Giving nice illumination up close all the time.

If you want to drive with just Fog lights, simply use the parking lights.

 

[Sequoiasoon]

When I wire my fog lights here is what I do.

I use a Hella relay that I normally install in engine bay. The power wire to it comes direct from battery with a fuse "30". One wire goes to the lights "87". The trigger power wire goes to the parking lights "86". The ground wire "85" for it goes to inside the cabin to the switch. The ground wire runs through a grommet or existing wire look area. My switches don't have indicator lights that they are on. I know when they are on or off.

The fogs won't come on if parking lights are not on. They stay on with low beam and high beam. If the ground wire ever shorts out worst case the fogs come on with parking lights.

Makes it pretty simple, not going through any ECU's, lets me run just fog lights and parking lights if really bad outside and headlights glare too much. If parking lights are left on the reminder beeps.

Relays with wires. The 87a wire is not used/taped off/removed.
Amazon Relays Many brands/versions here is one

 

[Nukeman7]

When I wire my fog lights here is what I do.

I use a Hella relay that I normally install in engine bay. The power wire to it comes direct from battery with a fuse "30". One wire goes to the lights "87". The trigger power wire goes to the parking lights "86". The ground wire "85" for it goes to inside the cabin to the switch. The ground wire runs through a grommet or existing wire look area. My switches don't have indicator lights that they are on. I know when they are on or off.

The fogs won't come on if parking lights are not on. They stay on with low beam and high beam. If the ground wire ever shorts out worst case the fogs come on with parking lights.

Makes it pretty simple, not going through any ECU's, lets me run just fog lights and parking lights if really bad outside and headlights glare too much. If parking lights are left on the reminder beeps.

View attachment 249059

This method is very sound; however, the OP does not identify in what state he resides. You will not pass a state safety inspection in certain states that prohibit running fog/driving lights with only the parking lights. This is the case in Virginia where the auxiliary fog/driving lights can only be legally activated when the headlight (low or high) beams are illuminated. In my experience, any DOT certified OEM fog/driving lights installed at the factory for vehicles sold in the U.S., they will be wired this way to comply with all 50 states.

 

[jsean]

Have you looked for OE wiring for them that may be tied or taped up close to the lights location. Does it have a location for the fog light switch in the dash? There may be wiring already there for them.

I did. Turns out Ford has separate wire harnesses for the SEL/SES trims that came with the fog lights from the factory vs. the S/SE trims that came without them. I’ve been looking for the Ford offered fog light addition kit in vain, for the past year.

Spent about 2 hours this morning at the pick n pull trying to verify the harness outputs/wiring is different on the SEL vs. my S.

 

[Leo99]

Oh ok and I assume you didn’t notice any issues? That should make it much faster for me. I’ve been disconnecting/reconnecting the negative cable and it’s starting to get annoying doing it several times…

That it never occurred to me to disconnect the neg terminal means that I'm not an expert in this area.

When I installed fog lights in my 1986 Honda, I had a wiring schematic and tapped into the low beam wire with a splice. So it only had power when the low beams were on and it turned the fog lights off when the low beams off or the high beams on.

 

[jsean]

The fuse boxes aren't for your convenience, they're for Ford's.

The way this car is laid out, your accessories run off the in-cabin fusebox while the ignition switch output basically returns to the under hood box. If you want a switched source, look there. Like others said, add a relay and things get better. I assume the ground in the passenger compartment is for the little light in the switch and for nothing else.

I'd tap the breaker for the sunroof and power windows. You get the added advantage of it being a self-resetting breaker if you do too much at one time.

The wiring harness I purchased already has a relay and a fuse, both of which are on the engine bay side of the harness.
I get that the fuse box is for Ford’s convenience, it’s just the number of fuse slots that show 12V with key out that threw me off. On the Corolla, circuits that don’t power on without the key do not have constant 12V.
Used my multimeter and found a few fuse slots on the LHS of the box that are switched. Tapped into one of them and I’m all set.

 

[jsean]

When I wire my fog lights here is what I do.

I use a Hella relay that I normally install in engine bay. The power wire to it comes direct from battery with a fuse "30". One wire goes to the lights "87". The trigger power wire goes to the parking lights "86". The ground wire "85" for it goes to inside the cabin to the switch. The ground wire runs through a grommet or existing wire look area. My switches don't have indicator lights that they are on. I know when they are on or off.

The fogs won't come on if parking lights are not on. They stay on with low beam and high beam. If the ground wire ever shorts out worst case the fogs come on with parking lights.

Makes it pretty simple, not going through any ECU's, lets me run just fog lights and parking lights if really bad outside and headlights glare too much. If parking lights are left on the reminder beeps.

View attachment 249059

Relays with wires. The 87a wire is not used/taped off/removed.
Amazon Relays Many brands/versions here is one

View attachment 249060

This is very helpful, thanks for sharing. I’ll follow this method the next time I need to wire up fog lights. With my current setup, I can run the fogs independent of all lights. So I can just have them on separately or with parking lights or with high/low beams. I don’t have inspection in my state, so I’m not particularly worried about that for now.

I did verify that if I have the fog light switched on and pull the key out, it kills power to the circuit. Joys of trying to make a strippie trim vehicle a little nicer

 

[jsean]

That it never occurred to me to disconnect the neg terminal means that I'm not an expert in this area.

When I installed fog lights in my 1986 Honda, I had a wiring schematic and tapped into the low beam wire with a splice. So it only had power when the low beams were on and it turned the fog lights off when the low beams off or the high beams on.

Fwiw, I didn’t bother disconnecting the battery this morning. Didn’t seem to matter!

I originally wanted to have it wired the way you did it, basically into the factory wiring harness but I wanted to the ability to run my fogs either with the low beams or just the parking lights. I went through several threads on the Focus forums and couldn’t find much for the US Mk2 model. So I ended up doing the add a fuse and run a separate harness with its own fuse and relay.