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Discussion Starter #1
My new LED reverse lights are not working. I just installed a pair of Sylvania Zevo 921 reverse light bulbs in my 2015 ST2. I got them installed but ended up breaking one of brake light bulbs (long story). When I tested them, they turned on for a split second, then turned off and won't go back on.

Is there some sort of trick to installing these? I'm not sure if these have resistors or not but Diode Dynamics says that no resistors are needed for the reverse lights. Could the broken brake light be causing this?

Any thoughts??

Thanks!

These are the bulbs I got LINK
 

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Well there could be several issues here.
They were installed reverse polarity. Halogen bulbs can be installed in any position.

The resistance on these bulbs are too low causes a fuse to blow.

You need to check the socket for 12 VDC.

I can put up the diagrams later this evening of you need.
 

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Discussion Starter #3
Well there could be several issues here.
They were installed reverse polarity. Halogen bulbs can be installed in any position.

The resistance on these bulbs are too low causes a fuse to blow.

You need to check the socket for 12 VDC.

I can put up the diagrams later this evening of you need.
Hey, I appreciate your reply. The diagrams could be useful, hope I can read them lol.

I have heard mixed responses about the polarity of these bulbs. Sylvania says the Zevo bulbs are not polarity sensitive, but I have seen a couple videos and posts about polarity issues. I have also heard that the polarity might be on the housing itself, not the bulb. I am not sure if Ford/ Focus is polarity sensitive from the factory or not. It's too dark out now to try and reverse the direction of the bulbs but I will try that tomorrow.

I have not checked the fuse, and I am not sure which fuse to check specifically. I looked for a fuse diagram a while ago and was unable to find one. If you have one it would be really helpful.

What is 12 VDC?

Thanks!
 

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I'll lay everything out for you after I get my daughter to bed.

J
 
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Well batter up kids because here we go again.

With the understanding that you need to have a grip on basic automotive 12 volt (if not I have written about this previously) we'll move right into how the reverse lamps work.

The Focus 5 door (our ST's) reverse lamps receive their power from Fuse F76 (10 amp) on the BCM (body control module) located under the passenger side foot well cover.
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After the reverse lamp switch is engaged the PCM (powertrain control module) transmits the appropriate command to the BCM over the vehicles CAN BUS network. So remember that there is no direct connection between the lamp switch and the reverse lamp relay.

Once this signal is received by the BCM it energizes the reverse relay sending power to the tail light connectors C414 (gray - violet wire 12 +) & C417 (green - brown wire 12+) both on Pin 5.

Ground is supplied on Pin 1 (black - white) also on both connectors.

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If you don't have access to a DMM (digital multimeter) you can reinstall one of the halogen bulbs to ensure that you have power on fuse F76.

Let me know if you need any help.

J
 

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Discussion Starter #6
This is fantastic! Thank you. I didn't realize the reverse light system was this complex lol. I could sit here for a long time trying to fully understand the system.

So the negative wires are Grey / Violet on the left, Green / Brown on the right?

I am going to try and reverse the bulbs in their sockets first, if that doesn't work I will work backwards to the Fuse. So because there is no direct connection between the BCM and the PCM, the car doesn't throw up a code if the load is too low (LED) or is burnt out? And vice versa for bulbs, like the turn signals and brake light that are connected directly to the PCM and throw codes if something is off?

Thanks again, this is awesome!
 

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Discussion Starter #8
So Quick Update. I pulled the fuse and it was blown, replaced the fuse again and it immediately blew. Did the same thing as last night. The drivers side reverse light came on for a split second then blew the fuse.

Any thoughts on what might be going on??

Thanks!


A white FSwerks Tuned, Steeda Breathing, Straight Piped, Symp Deleted 2015 FoST-2 wrapped in Indy 500’s. - SD
 

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So Quick Update. I pulled the fuse and it was blown, replaced the fuse again and it immediately blew. Did the same thing as last night. The drivers side reverse light came on for a split second then blew the fuse.

Any thoughts on what might be going on??

Thanks!


A white FSwerks Tuned, Steeda Breathing, Straight Piped, Symp Deleted 2015 FoST-2 wrapped in Indy 500’s. - SD
I'd say the resistance is wrong and your LED's are drawing too much current.
 
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A circuit needs resistance to function. Zero resistance is known as a direct short to ground or you'll hear others refer to it as a "dead short".

The fuse is doing its job. Fuses protect wiring from damage, not the load or device (lights, motors, etc.).

If you replace the aftermarket for the factory halogen bulbs and the issue stops then the LED's will not work for your application.

If the fuse blows again with the halogen bulbs installed then you could potentially have a damaged wire or connector.

J
 

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Discussion Starter #11
I'd say the resistance is wrong and your LED's are drawing too much current.

They shouldn’t be, they are draw 2.5W @ 12.8V, which is much less than the standard halogen bulb which draws 18W @ 12.8V.


Could it be an issue with the wiring from when I pulled it out last night? Or an issue with the bulbs themselves? I just got a new pack of the bulbs. Also the back of the box says a load equalizer may be necessary in some applications for whatever that’s worth.

I am going to pull the housings off and check but the LED brake lights I installed today work perfectly so I dunno...




A white FSwerks Tuned, Steeda Breathing, Straight Piped, Symp Deleted 2015 FoST-2 wrapped in Indy 500’s. - SD
 

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Discussion Starter #12
A circuit needs resistance to function. Zero resistance is known as a direct short to ground or you'll hear others refer to it as a "dead short".

The fuse is doing its job. Fuses protect wiring from damage, not the load or device (lights, motors, etc.).

If you replace the aftermarket for the factory halogen bulbs and the issue stops then the LED's will not work for your application.

If the fuse blows again with the halogen bulbs installed then you could potentially have a damaged wire or connector.

J
I am going to pull the housings off and check the connection for the reverse lights. It only seems to work for a split second on the drivers side. What should I be looking for wiring wise other than the obvious unplugged wire lol


A white FSwerks Tuned, Steeda Breathing, Straight Piped, Symp Deleted 2015 FoST-2 wrapped in Indy 500’s. - SD
 

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Discussion Starter #13
Update: the problem has resolved itself. *apologies in advance for any incorrect terminology, I am the furthest thing from an electrician.

I removed both housings, inspected all the wires/ harnesses/ connectors I could find on what I thought to be the reverse circuit (found no cut or damaged wiring), but I secured the taillight wire bundles w/ extra elec. tape where the OEM wire wrap stopped short of the light harness. I also returned the Sylvania 921 bulbs and tried the same thing but in 912... not sure why I thought that would make a difference but I tried it anyways.

Next I replaced the 10A in slot 76 in the Passenger footwell and re-installed the OEM halogen reverse bulbs. I tested them independently, both worked fine. Then I put the new 912 LED in the drivers side and tested, then the same for the other side.... both worked perfectly with no blown fuse! No issues over the past couple days and they are super bright.

My guess is one of the bulbs was faulty or the exposed wire bundle behind the passenger side housing was somehow shorting on the frame.

Thanks for everyone’s help!


A white FSwerks Tuned, Steeda Breathing, Straight Piped, Symp Deleted 2015 FoST-2 wrapped in Indy 500’s. - SD
 
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