Disco Magic

Active Member
Hi all, I’m about at my wits end and would appreciate any advice before sending the old girl into a garage.

I’ve got a 2006 FL1 td4 and whilst out at the weekend the 2 amigos came on, TC and HDC. I was near home and once back realised I’d lost my brake lights, I also checked the fuses and No 2 under the dash for brakes and reverse lights was blown.

Hawkeye showed (for Mk 25 ABS):
5E17 - Can gear - plausibility
5DF4 - Voltage low
5E5D - BLS electrical fault

I cleared the faults.

I came straight here and found to replace the brake light switch - although clue was in the BLS fault. Of all things I’d bought the upgraded switch and wiring loom adapter many years ago when I had a brake light problem but I couldn’t get the old switch out then and suddenly it started working again so I left if.

No such luck this time and I finally realised the old switch had been badly mullered in at a previous time and was only coming out with equal force, the bayonet didn’t look pretty when I got it out.

After fitting the new switch and replacing the fuse it worked temporarily then blew the fuse again. I replaced the fuse several times, sometimes it would blow while stationary others it would last for a short test drive then blow, always putting the 2 amigos back on.

I also disconnected all three brake light units and pressed the brakes but that didn’t blow the fuse.

No fault codes ever appeared with upgraded switch installed.

Yesterday I ordered another new switch but of the original fitment XKB100170 type. Fitted that today and for a while thought all seemed good except brake lights only worked with a very hard press rather than a touch of the brakes. Pressed the brake pedal about 50 times on the drive and was working (apart from the hard press).

I should say all brake presses have been a mixture of brakes only or brakes and reversing lights but clearly they blow while driving and reverse not selected.

Short test drive and 2 amigos on again and blown fuse.

Replaced fuse and it blew at first press of brake pedal.

Hawkeye now showing 5E5D BLS fault again with the new XKB100170 switch installed. No other faults.

As I say, now at my wits end and would appreciate any pointers.

Sorry for such a long post.
 
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It's not the brake light switch, so put back the one that cones on before the brakes come on. ;)

I suspect you have a short circuit in the brake light wiring somewhere. I can't remember if there's a relay for the brake light, but something in the old grey matter says there is.

You'll need to carefully check the wiring from the lights themselves, all the way to the front fuse box.
However I'd start at the tail door wiring first, where the wires go through the hinge gaiter.
 
It's not the brake light switch, so put back the one that cones on before the brakes come on. ;)

I suspect you have a short circuit in the brake light wiring somewhere. I can't remember if there's a relay for the brake light, but something in the old grey matter says there is.

You'll need to carefully check the wiring from the lights themselves, all the way to the front fuse box.
However I'd start at the tail door wiring first, where the wires go through the hinge gaiter.

Thanks, I’ll look at the tail door wiring in the morning. I must say I wasn’t planning to keep this brake switch which only illuminates with a near emergency stop but I was clutching at straws fitting it. I’ll also check if there’s a relay.

Sounds like a ball ache to check wiring from lights to the fuse box. Is it worth getting an auto electrician to check it? Am I right that professional multimeters/testers can locate how far a break or short is along the wire?
 
To check it's a case of breaking it down into smaller pieces. Checking half way, then check the bad half and so on.
The problem you don't want is if you start then decide to take to a garage have you introduced faults and bad connections yourself.
 
You've probably sussed this already but just in case - when you mention some difficulty fitting or removing brake light switches - if you remember to push down the pedal by hand the bayonet fitting pops straight in and out easily - if you don't its very difficult to do it without some damage.
 
Things have got stranger today.

I’ve refitted the upgraded switch and loom adapter. Brake lights now at slightest touch again :)

I called a couple of garages yesterday, neither could look at it until the new year.

Second chap was very helpful and asked everything I’d checked. Told him I’d had all the light units out. He suggested taking two out again and keep checking with just one connected at a time. Sod’s law everything was OK and it didn’t blow the fuse however long I pressed the pedal.. He also suggested another close inspection of the lamp holders.

High level bulb was blackened although working so I hoped I’d found the problem. Checked the lower two with constant brake for a couple of mins, no problems. Didn’t have a spare bulb for the high brake but hoped I’d found the culprit. Bulb holder still looks perfect.

Short test drive was fine so went out this afternoon on my rounds. Still without the high level bulb as a “test”.

After about 10 miles I had a reasonably heavy stop, not emergency stop, and 2 amigos came on - fuse blown. Replaced fuse and it blew at slightest touch of the pedal. Fitted another fuse and it was OK again, for the time being.

But, I hadn’t mentioned before another annoying but intermittent fault I’ve got: door locks rapidly clicking unlocking all the while. I hadn’t had it for a while but it started again at same time as the 2 amigos and blown fuse.

I wonder if it’s a short somewhere between the locking system and the brake lights. It’s either linked or a huge coincidence.

I also have a knackered window regulator in the OSR door but I pulled the fuse the other day to isolate that.

It took me 3 brake light fuses to get home and I felt pretty vulnerable so I need to find the root cause now.

Will strip the tail door tomorrow and go from from there. I got some spare bulbs today too.

Otherwise, would it be feasible to simply forget looking for shorts and rewire the brake lights from the fuse box?

A final thought, I also took the trailer socket off and it all looked fine and clean. Perhaps I should find where it meets the main wiring loom and disconnect it. I don’t tow with this car so anything to get the brake lights 100%.

thanks

Edit
I should of course had said would it be feasible to rewire from the brake switch to the lights rather than from the fuse box.

It’ll be a lot easier to chop into the adapter wiring for the new switch.

I’ll still strip the tail door out, if that’s OK I’ll check from all lights back to where the wiring splits but sending a new wire back might be easier if there’s nothing glaring.
 
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Things have got stranger today.

I’ve refitted the upgraded switch and loom adapter. Brake lights now at slightest touch again :)

I called a couple of garages yesterday, neither could look at it until the new year.

Second chap was very helpful and asked everything I’d checked. Told him I’d had all the light units out. He suggested taking two out again and keep checking with just one connected at a time. Sod’s law everything was OK and it didn’t blow the fuse however long I pressed the pedal.. He also suggested another close inspection of the lamp holders.

High level bulb was blackened although working so I hoped I’d found the problem. Checked the lower two with constant brake for a couple of mins, no problems. Didn’t have a spare bulb for the high brake but hoped I’d found the culprit. Bulb holder still looks perfect.

Short test drive was fine so went out this afternoon on my rounds. Still without the high level bulb as a “test”.

After about 10 miles I had a reasonably heavy stop, not emergency stop, and 2 amigos came on - fuse blown. Replaced fuse and it blew at slightest touch of the pedal. Fitted another fuse and it was OK again, for the time being.

But, I hadn’t mentioned before another annoying but intermittent fault I’ve got: door locks rapidly clicking unlocking all the while. I hadn’t had it for a while but it started again at same time as the 2 amigos and blown fuse.

I wonder if it’s a short somewhere between the locking system and the brake lights. It’s either linked or a huge coincidence.

I also have a knackered window regulator in the OSR door but I pulled the fuse the other day to isolate that.

It took me 3 brake light fuses to get home and I felt pretty vulnerable so I need to find the root cause now.

Will strip the tail door tomorrow and go from from there. I got some spare bulbs today too.

Otherwise, would it be feasible to simply forget looking for shorts and rewire the brake lights from the fuse box?

A final thought, I also took the trailer socket off and it all looked fine and clean. Perhaps I should find where it meets the main wiring loom and disconnect it. I don’t tow with this car so anything to get the brake lights 100%.

thanks

Edit
I should of course had said would it be feasible to rewire from the brake switch to the lights rather than from the fuse box.

It’ll be a lot easier to chop into the adapter wiring for the new switch.

I’ll still strip the tail door out, if that’s OK I’ll check from all lights back to where the wiring splits but sending a new wire back might be easier if there’s nothing glaring.
Sounds like it could be an issue around the main harness, where it comes out of the CCU. There's a lot of exposed metal structures around the CCU/fuse box, and the harness has been known to wear through where its been rubbing on the metal.
Thanks, I’ve got a manual so assume they just fitted the same built up brake pedal.
The EDC also uses that sensor, so it knows you're braking, even if it's receiving a throttle signal. ;)
 
Sounds like it could be an issue around the main harness, where it comes out of the CCU. There's a lot of exposed metal structures around the CCU/fuse box, and the harness has been known to wear through where its been rubbing on the metal.

The EDC also uses that sensor, so it knows you're braking, even if it's receiving a throttle signal. ;)

Thanks, I’ll check around the CCU/fuse box before stripping the tail door.

I assume you’re thinking damage to both the brake light a the central locking wiring.

Probably worth ordering the second brake switch too then.
 
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Thanks, I’ve got a second little square switch but wonder if it’s superfluous to requirements as it’s cruise control stop which I don’t have.

Does you know if it would still throw a fault?
No I never had fault codes. Only when trying to install cruise control box which didn't work, LR told to check on that one as it would only be 12£ or so. Changed it and it worked. Don't why LR what install if no cruise control in. I felt it drove different after changing it, but that could just be me.
 

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