Hi everyone my first post, My other half has noticed, due to being flashed many times last night, that all 3 rear lights have stopped working (Her brake lights are fully working).

What would you guys suggest to look at? Earth points (no idea where these are), rusty connectors or relay?

Thanks in advance!

So you mean the normal tail lights (just the 2!) but reverse, indicator and brake all still work?  Possibly a fuse if that's the case.

Yeah sorry just the two rear lights not working, reverse, indicators and brakes are working fine.  I'll check the fuses first later but i would be surprised if both sides went at the same time. thanks for the help.

I would start with the bulbs. Change one and see if it works.

I've changed the rear brake bulbs but still no rear lights. I changed the fuses for both left and right  lights but still no joy? all 4 side lights are out too but i got the wrong bulbs to change them so will do this tomorrow. Could this be the dipped beam relay? it still wouldn't make sense that the front beams run if the relay was damaged.

Anymore help would be appreciated. 

Thanks

2 hours ago, tomfiestamk7 said:

all 4 side lights are out too

So all the tail/side/parking lamps are out?

Sounds like the light switch, or its wiring to the BCM. That would be the only common element I can think of.

If my diagram is right, then the switch goes to C5-9 on the BCM, with a Yellow/Blue wire.

(Where exactly C5 pin 9 is on the BCM, I have no information, unfortunately!)

 

3 hours ago, Tdci-Peter said:

So all the tail/side/parking lamps are out?

Sounds like the light switch, or its wiring to the BCM. That would be the only common element I can think of.

If my diagram is right, then the switch goes to C5-9 on the BCM, with a Yellow/Blue wire.

(Where exactly C5 pin 9 is on the BCM, I have no information, unfortunately!)

 

Can you show real schematics ? BTW, can you help me real schematics for wiring footwell light ( if you have ).

I have diagram, so I dont know how to wire footwell light.

On 7/27/2016 at 1:54 AM, notfourgo said:

Can you show real schematics ?

Nope!

All I have is some partial printouts of the diagram. It is extremely difficult extracting these from the Ford system, to which I don't have access anyway!

The only thing I can add is the connector numbers:

C3-5 is the Interior Lamp pin (The -ve terminal from the footwell & other interior lamps.)

C3-4 is the Battery Saver Relay ( The +ve terminal to the footwell & other interior lamps. )

The connectors on the BCM (GEM) go from C1 to C7, also may be called BCM_A to BCM_G.

The colour codes (Gn/Vt & Yw/Gy) match.

PDF that I have is attached.

https://www.fordownersclub.com/applications/core/interface/file/attachment.php?id=41035

 

22 hours ago, Tdci-Peter said:

So all the tail/side/parking lamps are out?

Sounds like the light switch, or its wiring to the BCM. That would be the only common element I can think of.

If my diagram is right, then the switch goes to C5-9 on the BCM, with a Yellow/Blue wire.

(Where exactly C5 pin 9 is on the BCM, I have no information, unfortunately!)

 

yes all tail/side/parking lamps are out apart from front beams. I took the switch out and used a voltage tester but it didn't detect any voltage along the C5-9 wire at the switch end. I've got a relay coming tomorrow so will try that out. anymore ideas? 

3 hours ago, tomfiestamk7 said:

voltage tester but it didn't detect any voltage along the C5-9 wire at the switch end.

Wire C5-9 is just a thin signal wire, it does not carry power for the bulbs.

Either the BCM energises this wire, and the light switch grounds the wire to operate the lights,

Or there is a low power 12v to the switch, and the switch sends this to the BCM to operate the lights.

 

I think the first option is more likely. Testing the other wires into the switch connector would help, if several had 12v or 5v, and one was grounded, then that would match the 1st option. A Haynes diagram would also help.

If it is the 1st option, and there is no voltage at the switch end, the next stage is to test that wire (C5-9) at the BCM. Might be easier said than done, it depends whether the BCM operates ok with that connector removed, and how easy it is to probe individual pins.

If it is the 2nd option, then the switch might be faulty, as the other lighting functions work.

What I can see is that the 12v power for the lighting goes through F22 in the Engine bay fuse box, and into the BCM at C1-7 (Bn-Rd). This powers more than just the sidelights. The BCM then seems to energise the four side lights separately and directly. So it is all controlled in the electronic module.

See if the relay helps, though I can't see where that fits in.

 

12 hours ago, Tdci-Peter said:

Wire C5-9 is just a thin signal wire, it does not carry power for the bulbs.

Either the BCM energises this wire, and the light switch grounds the wire to operate the lights,

Or there is a low power 12v to the switch, and the switch sends this to the BCM to operate the lights.

 

I think the first option is more likely. Testing the other wires into the switch connector would help, if several had 12v or 5v, and one was grounded, then that would match the 1st option. A Haynes diagram would also help.

If it is the 1st option, and there is no voltage at the switch end, the next stage is to test that wire (C5-9) at the BCM. Might be easier said than done, it depends whether the BCM operates ok with that connector removed, and how easy it is to probe individual pins.

If it is the 2nd option, then the switch might be faulty, as the other lighting functions work

What I can see is that the 12v power for the lighting goes through F22 in the Engine bay fuse box, and into the BCM at C1-7 (Bn-Rd). This powers more than just the sidelights. The BCM then seems to energise the four side lights separately and directly. So it is all controlled in the electronic module.

See if the relay helps, though I can't see where that fits in.

After all the messing around with switches etc it ended up being fuse F22 15a lighting control battery supply! still no idea why the front beams worked, maybe because the previous owner has installed HID lights. Thanks TDCI Peter, all lights work perfectly now.

 

On 7/18/2016 at 9:31 AM, tomfiestamk7 said:

Hi everyone my first post, My other half has noticed, due to being flashed many times last night, that all 3 rear lights have stopped working (Her brake lights are fully working).

What would you guys suggest to look at? Earth points (no idea where these are), rusty connectors or relay?

 

Thanks in advance!

 

Did you ever fix this problem 

6 hours ago, Masdan96 said:

Did you ever fix this problem 

After all the messing around with switches etc it ended up being fuse F22 15a lighting control battery supply! still no idea why the front beams worked, maybe because the previous owner has installed HID lights. Thanks TDCI Peter, all lights work perfectly now

Gazcaz, it was definitely F22? On my fuse diagram it says F22 is an unused Fuse. I've got a Mk7 Fiesta ST with the exact same problem.