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2016 Focus ST3
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Discussion Starter · #1 ·
So I got a weird one. Car is a 2016 Focus ST. Last night about bed time the wife asks me why my tail lights are on and I say they are not. She insists so I go look, they are on, but SUPER dim. Not like the parking lights are on, but just a small ambient glow, somehow they are getting small voltage?

I went out there, checked the doors, checked the light switch. Everything looks good. Locked it, lights still on. I saw the car do this another time but the lights actually shut off so figure "Tech happens" and go to bed.

I bought the car used and it seems to have some stories. Looking in the lens, there are what look like aftermarket LED tail lights in there.

Now, another oddity is the DRLs on this car. If a door is open, only the drivers side turns on. If you turn on the headlights, then both DRLs are on.
 

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2014 ST3. Garrett GTX2860R Gen 2. FBO
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It's the LED bulbs. They cause more issues than they're worth. Get rid of them.


 

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So just normal halogens and my problems go away? Say it ain't so!
I don't have any hyper flash problems.
Yep!
It's likely some sort of backfeeding issue if I were to guess. Resistance Sensing circuits do not take kindly to this kind of thing.
 

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Well snap. Off to the store!
I really hope this shores it up, could go for an easy win!

Do LED fogs cause problems, too?
I don't believe so. Only the more delicate circuits.

I've been running Diode Dynamics Luxeon fog lights (full housing replacements) for a couple years now with no adverse issues.
 

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2017 Kona Blue ST1
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Schematic Rectangle Font Material property Parallel


Okay here's the reality of this (and most) systems. Gone are the days of direct wiring and large separate relays & switches. As the need to make vehicles lighter and to reduce costs as well as the demand for more modern styling the traditional electrical design gave way to compact transistor based circuits.

Relays were originally introduced as a way to use a smaller more ergonomic switch to trigger a larger load. Think aftermarket fog lights. You couldn't pass 30 amps through a small toggle switch for very long without something burning up.

Modern auto manufacturers have taken this a step further. Now the bulk of switching is handled by a BCM (body control module) or separate remote module (door, audio, etc.).

Some use a smaller more traditional relay that is soldered onto the BCM main board.
This sucks because they can fail just like an other relay but are not serviceable by the end user.
Passive circuit component Circuit component Blue Green Product

The smaller relays can been seen here either small black or white squares. They have two parts 1. Contact (switch) & 2. Coil (magnetic force that closes the contact).

The contact is either open or closed. They can become worn or burnt and in the worst-case scenario fused together from heat. The coil can fail from wear.

These relays and other lighting not controlled by relays are switched by transistors.
Eye Gesture Font Parallel Circle

This switching method doesn't have moving parts but operates similar to a relay (smaller current to switch a larger one) they can be very easily damaged by being forced to switch too high a load.

Cheap LED lights can effect how the BCM is looking to control the circuit. So do your research and try to purchase from a reputable company. They may seem expensive but it's still cheaper than the cost of a new BCM & reprogramming.

J
 

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View attachment 404117

Okay here's the reality of this (and most) systems. Gone are the days of direct wiring and large separate relays & switches. As the need to make vehicles lighter and to reduce costs as well as the demand for more modern styling the traditional electrical design gave way to compact transistor based circuits.

Relays were originally introduced as a way to use a smaller more ergonomic switch to trigger a larger load. Think aftermarket fog lights. You couldn't pass 30 amps through a small toggle switch for very long without something burning up.

Modern auto manufacturers have taken this a step further. Now the bulk of switching is handled by a BCM (body control module) or separate remote module (door, audio, etc.).

Some use a smaller more traditional relay that is soldered onto the BCM main board.
This sucks because they can fail just like an other relay but are not serviceable by the end user.
View attachment 404118
The smaller relays can been seen here either small black or white squares. They have two parts 1. Contact (switch) & 2. Coil (magnetic force that closes the contact).

The contact is either open or closed. They can become worn or burnt and in the worst-case scenario fused together from heat. The coil can fail from wear.

These relays and other lighting not controlled by relays are switched by transistors.
View attachment 404120
This switching method doesn't have moving parts but operates similar to a relay (smaller current to switch a larger one) they can be very easily damaged by being forced to switch too high a load.

Cheap LED lights can effect how the BCM is looking to control the circuit. So do your research and try to purchase from a reputable company. They may seem expensive but it's still cheaper than the cost of a new BCM & reprogramming.

J
I’m a helicopter Electronics/Avionics technician and can confirm everything SSgt just said.

Led bulbs, without a resistor, placed in a circuit designed for halogen bulbs will result in a slight constant illumination.
 

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2016 Focus ST3
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Discussion Starter · #10 ·
The DRLs are still weird. When a door is open the drivers' side lights up only. Turn on the car and both are on.

It's getting dark and will oogle for demonic glows from the rear of the focus.
 

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2014 ST3. Garrett GTX2860R Gen 2. FBO
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Are there any other aftermarket LEDs installed in any other parts of the system that turn on when the door is opened? Puddle lights, interior lights, etc?

Also worth asking, did you disconnect the battery? I'm just wondering if that DRL circuit is in some sort of protection mode due to the issues previously experienced by the other LEDs. My thought is if it is, the battery disconnect will reset that.
 

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Discussion Starter · #12 ·
I can disconnect the battery. Not really sure what the prior owner has done. Did not see puddle lamps on this car. Did not check side markers or other existing lights.
 

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2017 Kona Blue ST1
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Battery age? (Sorry if I've asked before but I help with a lot of different issues and can't keep then all straight LOL!)
 

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Okay, the reason I ask is I've seen where low or under performing system voltage will cause all strange manner of electrical issues. There's nothing else tied into the battery that is wired constantly hot is there? Amps or such? (Again I apologize if I've asked before)
 

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Discussion Starter · #16 ·
Okay, the reason I ask is I've seen where low or under performing system voltage will cause all strange manner of electrical issues. There's nothing else tied into the battery that is wired constantly hot is there? Amps or such? (Again I apologize if I've asked before)
Oh, believe me I have seen some weird things with bad batteries... On my truck I would start it, drive it and slowly roll throttle and the whole truck would cut out, motor and all electronics. Take foot off gas and it would spring to life. That was a fun one to pin down.

At this time, there are no auxiliary items I have added to the car which IMO should cause problems. I have replaced the front speakers, cleaned some grounds. Other mods: Tune, FMIC, catch can, exhaust, diverter valve, replaced the HID bulbs(used Sylvania), upgrade & jailbroke sync, replaced USB port in console to allow carplay, did some forscan things (mostly enable fogs with high beams, set country code from CA to USA), true vac on diverter valve. The fog lights are LED(came with car) but are slated to be replaced with something better down the road.

While the DRL is not a huge issue, its peculiar and weird. I've also noted at times when the car is off the needles in the cluster sometimes 'dance', I think its the tach needle does this.

Do these come with interior LED lights outside of the color changing mood lights? It does appear the map lights and possibly the hatch lights are LED (6000k looking). The prior owner did have some LED underbody lighting on there, the remains of the wiring was strung around under the car with zip ties but has since been removed.
 

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Oh, believe me I have seen some weird things with bad batteries... On my truck I would start it, drive it and slowly roll throttle and the whole truck would cut out, motor and all electronics. Take foot off gas and it would spring to life. That was a fun one to pin down.

At this time, there are no auxiliary items I have added to the car which IMO should cause problems. I have replaced the front speakers, cleaned some grounds. Other mods: Tune, FMIC, catch can, exhaust, diverter valve, replaced the HID bulbs(used Sylvania), upgrade & jailbroke sync, replaced USB port in console to allow carplay, did some forscan things (mostly enable fogs with high beams, set country code from CA to USA), true vac on diverter valve. The fog lights are LED(came with car) but are slated to be replaced with something better down the road.

While the DRL is not a huge issue, its peculiar and weird. I've also noted at times when the car is off the needles in the cluster sometimes 'dance', I think its the tach needle does this.

Do these come with interior LED lights outside of the color changing mood lights? It does appear the map lights and possibly the hatch lights are LED (6000k looking). The prior owner did have some LED underbody lighting on there, the remains of the wiring was strung around under the car with zip ties but has since been removed.
Your st3 would have the factory-location lights in LED. I should have been more clear, I was leaning toward any add-on footwell lighting, or door sills, stuff like that.


You mentioned enabling Bambi mode in forscan. It is possible there is something goofy related here. Although I have no experience with doing that mod.

I will say on my '14, I went in there and disabled my double-honk. Well in doing that, the interior lights quit working. I'm the only person that had that issue that I know about. So I had to return it to stock.

Might be worth a try to reverse that feature and see if It changes anything.
 
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