Technical fog light help!

[steveras57]

Hi my rear fog light has stopped working and its not the bulb!
Anyone know what the next most likely problem area might be!?>
Are the dash switch known to fail! or might it be the dreaded hatch wiring! any help or ideas appreciated!
cheers
Steve

 

[varesecrazy]

Worth a quick look at the wiring where the tailgate hinges.

 

[porta]

Check bulb connections on lamp and the earth

 

[John202020]

First are the headlights on?
Does the tell tale come on, on the dash
Next remove the rear cluster, remove and inspect the connector
Do you have a test meter to check the voltage
It's not unheard of for the wire to break internally, this is not a hatch wiring issue

 

[steveras57]

First are the headlights on?
Does the tell tale come on, on the dash
Next remove the rear cluster, remove and inspect the connector
Do you have a test meter to check the voltage
It's not unheard of for the wire to break internally, this is not a hatch wiring issue

Hi
yes tested with headlights on
yes the warning light does come up in the cluster
rear connector looks sound as do any wires i can see before they disappear behind the rear panel the rear bulb holder looks ok too! goingb to test with meter later once home will post findings!
Is there a particular area in which the wire is prone to break and do yiou know the colour wire i should look for!
cheers
Steve

 

[John202020]

Brown with a grey stripe, breaks where it gets flexed, which is not much in your case.
Inside the boot poke a sharp blade through the insulation to see if there's a voltage assuming nothing at the bulb/connector, check the earth too?

 

[steveras57]

As near as i can tell there is no voltage at the connector to the bulb holder i can only trace the wiring back as far as the carpet over the rear panel by the back seat ,I assume it then runs through or next to the drivers sill plate under the carpet and comes up somewhere near the drivers door to run up towards the dashboard!.
To be honest i am having trouble understanding how the wire has broken? because there is no place it moves or flexes!.

Do you think that despite the warning light coming up on the dash the fog switch might be faulty? or more accurately i guess the curcuit board that controls all three switches, finally is there a relay that operates the fog light and which one in the engine bay fuse box is that please!.
thanks once again.
Steve

 

[John202020]

No relay, pin 10 at the bcm it has been reported once or so re dash switch fault

 

[steveras57]

Thanks for that! where is the body computer module located so i can check the connectors please!

 

[The Panda Nut]

Wires just break. I had a heated window wire fail in the loom inside the boot a few years back. I was told to feel along teh wire and look for a hot spot. This might still work for the fog lamp. I found the break and soldered in a new section. Unfortunately traing wires is time consuming. If removing cill trims go steady as the retaining clips can be very brittle.

 

[steveras57]

Gonna try to check the continuity from the switch to the bulb holder over the weekend! will post findings!

 

[steveras57]

Today as suggested i striped back a bit of insulation from the fog light feed wire(grey/brown) behind the boot panel carpet and tested it with a multi meter set to volts!- ignition on, headlights on, fog lamp switch pressed & symbol showing as active in dash board!.
red probe to the fog lamp wire -black probe to earth ITS ONLY READING 5.27 VOLTS which implys a short in the system somewhere to me!
opinions please!.
thanks
Steve

 

[steveras57]

More info
PLUGED my laptop in and used MES to check things!- NO fault codes in body computer ! but when using the activator function to in theory turn on the rear fog light it had no effect! despite the warning light coming on in the dash and the system saying completed! ( it did work on other functions such as indicators and headlights!.
Beginning to wonder if i might have a dry joint or poor connection in the bcm itself! would that account for the low voltage reading found in the wire i checked earlier??

 

[John202020]

More info
PLUGED my laptop in and used MES to check things!- NO fault codes in body computer ! but when using the activator function to in theory turn on the rear fog light it had no effect! despite the warning light coming on in the dash and the system saying completed! ( it did work on other functions such as indicators and headlights!.
Beginning to wonder if i might have a dry joint or poor connection in the bcm itself! would that account for the low voltage reading found in the wire i checked earlier??

I don't know the location of the BCM but once found I'd check the voltage on the fog light wire should be the same colour

 

[steveras57]

Hi John 202020
bcm is behind/under the passenger side glove box/shelf a right pain to get to and held in by 3 bolts! ( you have to take of 6 to get the glove box thingy out the way!)- there are 5 electrical connectors to the thing so thats a mighty lot of wires to sort through to find the fog light wire! grey /brown.

When you say check the voltage i guess you mean i have to have the power input cable connected and find the pin that SUPPLIES that brown /grey wire to see if the bcm is putting the right voltage out to feed the fog light! (regarding i have said that i now know that i am only getting 5.27 volts at the brown/grey wire just before the connector to the rear light unit).

I assume that if the voltage is low or missing! then there is an internal fault with the bcm?.

IF the voltage was found to be correct then i would check the continuity if the brown/grey from the bcm connector to the point where I measured the voltage near the back light connector!.
thats all i can think of to do at present!.
thanks for your help and replies
Steve

 

[John202020]

I had low voltage once on a non working boot light, but had power at the supply end, where the cable turned a corner it failed, might add it was one I installed only working along the cable taking readings showed what section was at fault hence why I wondered if this is the issue.
Given how infrequently the fog light is used I would not suspect the bcm?
However its been reported, blocked "duck bills" in the engine bay can allow water to get into the interior possibly onto the bcm or connectors?
Try tracing the loom back to the front, anywhere near the front that's able to be accessed check the voltage, if it's still low on a few feet from the bcm then maybe bolts need removing?

 

[steveras57]

When you say power at the supply end i take it you mean proper 12 volts there and lower at the boot light hence a fault in the cable!.
to check the loom nearer the bcm next stage will be near the drivers seat as its a ton of work to remove the rear interior quarter panel trim if the readings still low at that point then i will have to work nearer under the dash to try to trace back to the bcm( sounds like a world of pain as the loom must pass through /behind the whole dash as the bcm is located in the footwell on the passenger side!) if its ok at the drivers seat then the faults likely to be under that dreaded quarter panel