2015 Fiesta SE Hatchback no license plate lights

[Maximenis]

Hi everyone! I've searched through many a thread here and couldn't find an answer. I have a 2015 SE Hatchback and my license plate lights do not turn on. I replaced the bulbs with OEM bulbs, no go. I took apart the paneling, checking the wire harness and for the life of me I can't figure out where it connects to. I can see the rear wiper assembly, electronic latch, defrost, but I have no idea how to trace the wires back to, well for that matter, where? At one point my left brake light wouldn't light up when the lights were on (brake light worked), changed the bulb but still wouldn't light up, twisted some wires somewhere and all of a sudden started to work but still no license plate lights.

Is there a specific fuse or relay JUST for the plate lights? Anybody run into the same problem?

 

[Handy Andy]

Does the rear hatch "button" work?

If the Hatch release button won't work, then the wiring to the bulbs and that button has to be tracked down and repaired.

If the button works then the lamp problem is dealing with the individual wires to those sockets that use a #194 bulb.

Since the socket is bi-pin (two electrodes to make connection to the filament bulbs own "U" shape wires - there are only two U's and the socket is capable of using these U's bent over the other side or direction.

Why this? Well, the socket itself has to dissipate the heat from that bulb for the life of the bulb so as it tries to do that, it has to put that heat somewhere so it tries to transfer the heat to air and to the wires like heat sinks - but this tends to corrode or tarnish the copper electrodes as they age. The process is normal - it's a reduction of the copper and metal contact - thru current passing thru these leads - to their reduction or ore (oxidized) state.

Due to the nature of plastics and heat - they also "tensile" and retain a memory of their former lamp they mated with - so the contact may need cleaning or re-bending to reshape the contact to fit the new bulb in both location and fitment of pressure to light and retain the bulb in the socket.

What made them fail? Oxides, corrosion and water entry - can't avoid it in these cases.

So the housing might be OK, or not - what makes this tough is the type of socket and pigtail - that lamp uses - like a turn and twist to remove or insert - so if the seal on it's own grommet is bad, the lamp needs to be replaced as a unit.

 

[Maximenis]

Yes, the hatch works. Couldn't figure out past the hatch wiring where it goes into the tag lights. Will I need to re-harness everything? I will try to get the hatch release out of the way to take a deeper look at the exact wiring. I used a multimeter to see if I was getting any voltage off of one of the light sockets and I got nothing. Is it possible that somewhere the light sockets got unplugged? I also checked for oxidation, nothing really there. Thanks for the ideas, I'll see what I can do tomorrow!

 

[Handy Andy]

If possible the sockets and lamps are possibly OK, just the branch where the exterior lighting that goes to the 3rd brake light and also the tag lights - can get damaged - they are all wound together so if the trunk release works at the button, but the lights don't - you'll need to unscrew the two "coat hanger" points of trim on the rear hatch pillars and gently pry off the main rear panel to get in and look at the wiring.

There is a channel for the harness as it routes along the perimeter of the hatch interior - and the reinforcement is there also so it's not impossible that one wires been cut or worse shorted and now the burnout is further back towards where the upper hatch wiring by the hinge and pivot - snakes down to meet the rear brake lights - the Left side (ulp!) where you worked at before - if the wire opened up - this might be a good starting point.

 

[Maximenis]

If possible the sockets and lamps are possibly OK, just the branch where the exterior lighting that goes to the 3rd brake light and also the tag lights - can et damaged - they are all wound together so if the trunk release works at the button, but the lights don't - you'll need to unscrew the two "coat hanger" points of trim on the rear hatch pillars and gently pry off the main rear panel to get in and look at the wiring.

There is a channel for the harness as it routes along the perimeter of the hatch interior - and the reinforcement is there also so it's not impossible that one wires been cut or worse shorted and now the burnout is further back towards where the upper hatch wiring by the hinge and pivot - snakes down to meet the rear brake lights - the Left side (ulp!) where you worked at before - if the wire opened up - this might be a good starting point.

I did take off the panels to root around but I didn't take off the hatch release mechanism because I wasn't sure where the wiring for the plate lights comes out (the wiring is underneath some frame, not easily visible). I have to go a little more in depth before I can get to the junction and that will entail taking off the hatch release just to see.

One thing I was looking at was replacement LED's in their own housing. There is a pigtail coming off the housing with some sort of plug. Is the OEM housing the same, i.e. just a short pigtail and then connected to a receptor or are the wires part of a long harness? I'll root around a bit more later today (wife has the car lol, pretty much can only use during the day at this point).

Thanks for the insight, I'll take some pics to share so others can follow the ordeal!

 

[Handy Andy]

They are part of a longer harness. That finish metal (exterior painted) just "covers" and keeps the wiring dry, but the main bracing and "crash-worthiness" metal is behind it and is what the wiring snakes thru.

The pigtail itself just lets you connect when you cut off the old ones.

You may be able to locate the LEFT side wiring pigtail connector, (behind the felt of the Drivers side to rear brake tail-light. it has the running lights and tag lights TOGETHER on one pin, so the continuity check may require to you "backprobe" the wiring by the color code and locate which wire (Black with Green stripe or Black with Blue stripe) are grounds - as well as Black with Yellow stripe (if present) - all need to be checked to make sure these three wire coded color combinations are going to ground - it may help to use the multi-tester on the FRAME ground of the vehicle like the hatch's latch bolts - to verify voltage is going to the wires - if it's a bad ground - the wire may look "dead" or open because there it no return to the battery from that point. You complete the circuit by probing the live socket wire (to find it) and then checking it against a known good ground to the battery - completing the circuit - then you just have to find the break.

 

[Maximenis]

They are part of a longer harness. That finish metal (exterior painted) just "covers" and keeps the wiring dry, but the main bracing and "crash-worthiness" metal is behind it and is what the wiring snakes thru.

The pigtail itself just lets you connect when you cut off the old ones.

You may be able to locate the LEFT side wiring pigtail connector, (behind the felt of the Drivers side to rear brake tail-light. it has the running lights and tag lights TOGETHER on one pin, so the continuity check may require to you "backprobe" the wiring by the color code and locate which wire (Black with Green stripe or Black with Blue stripe) are grounds - as well as Black with Yellow stripe (if present) - all need to be checked to make sure these three wire coded color combinations are going to ground - it may help to use the multi-tester on the FRAME ground of the vehicle like the hatch's latch bolts - to verify voltage is going to the wires - if it's a bad ground - the wire may look "dead" or open because there it no return to the battery from that point. You complete the circuit by probing the live socket wire (to find it) and then checking it against a known good ground to the battery - completing the circuit - then you just have to find the break.

Got it. Gonna tackle this tomorrow when the wife is out with a friend and I can take everything apart. Thanks for the VERY clear idea (especially behind the felt). I had a feeling that the running lights and the tag lights were on one circuit since the left rear running light wouldn't come on although the brake light would work. Even though I changed the bulb the running light still wouldn't work until I pushed the bundle of wires around. I'm going to try to tackle that first to see if there's a bad connection there and post some pics of what I find.

Thanks again!

 

[Maximenis]

Turns out there was a split wire close underneath the junction by the tail light. I spliced the wires together and PRESTO! the plate lights started working. Thanks for the tip Handy Andy! You were spot on about checking the harness to make sure all the wires were intact. Is there a way to give you kudos?

 

[Handy Andy]

Just this post telling us we don't need to worry, you fixed it!

You deserve our congratulations in persevering thru this ordeal

A wrench or two for your efforts!


Drive on!

 

[Maximenis]

Interestingly enough, if anybody wants to know, in the pics you can see the license plate wire is green/purple. Just FYI if you have the same problem. I was able to trace this wire all the way to the hatch release and it was the same color code all the way. As Handy Andy mentioned, the bundle of wires/harness goes all the way up the rear pillar and down the driver's side of the hatch. I checked the bundle the whole way for any breaks. Like Handy Andy said, if the hatch release button works but the tag lights don't work, try to trace this particular wire all the way down. My biggest clue was that the driver's rear running light worked but the tag lights didn't. I figured that the cut would be somewhere after the junction to the brake/running light, and that's where it was!

Handy Andy - you are awesome!