Lost all rear brake lights!!!

[Banshee]

Guys, I'm struggling with a really weird issue at the moment that I'm hoping someone with previous experience with brake circuit wiring can help me figure out what on earth is going on :doh

So I've basically lost my high level brake light and my 2 rear brake lights in the high clusters.

I'll list what I've done and tried so far;

Checked 4th from left top row 15a tail lamp fuse in main fuse box
Checked 4th fuse from top in Auxiliary fuse box labelled "Tail"
Checked all bulbs
Slaved in two new confirmed working brake pedal switches
Checked voltage at bulb holders which reads 0.00v
Checked voltage further down the loom at the front passengers footwell kick panel which reads 0.05v

I slaved a wire from the positive feed on the rear 12v power socket directly onto the positive terminal of the high level brake light with the slave brake pedal switches hanging loose ensuring the circuit was closed and although the wire reads 12.6v the bulb only comes on very dim and the wire arcs lots when contact is made and gets very warm to the touch, I was using 17a cable

From this last test, should I be looking for an earthing issue or something else?

Has anyone else suffered a similar issue previously or that might be able to point me in the direction of other components I can test that I may have overlooked.

I'm stumped now but eager to have another go tonight as it's preventing me from using the truck again atm :doh

 

[jims-terrano]

Check towbar wiring for a short, socket and also where the cable inside the truck takes its feeds.

 

[Banshee]

Check towbar wiring for a short, socket and also where the cable inside the truck takes its feeds.

What a donut!!! I didn't check the towbar wiring.

Where does the cable inside the truck take it's feed, wiring diagrams aren't my strong point at the moment, I'm due some training at work on that subject though soon :thumbs

 

[jims-terrano]

Main wiring loom is passengerside behind plastic trims. Even if it’s been wired with the dedicated wiring kit that connects on outside behind bumper it must still take brake feed from inside vehicle.

Also take socket apart to see if it’s corroded or full of water.

Think there’s a towbar wiring Diagram in the downloads too.

 

[Banshee]

Main wiring loom is passengerside behind plastic trims. Even if it’s been wired with the dedicated wiring kit that connects on outside behind bumper it must still take brake feed from inside vehicle.

Also take socket apart to see if it’s corroded or full of water.

Think there’s a towbar wiring Diagram in the downloads too.

It appears that after tracing more wiring into the void behind the light cluster where it enters the body they have BUTCHERED wires to the original loom to attach the towbar wiring :doh

I'll attend to these later on as they have been done with Scotchlocks and look very very brittle like they have been there some years so could imagine one of these being a potential cause perhaps.

I'll take a look when I'm home from work in a few hours, got in early this morn so I can get my 5 hours out the way and have the rest of the day to myself

 

[jims-terrano]

Best get soldering iron and shrink wrap out then mate.

Take photos for your reference so you know which wire goes where. Then get rid of the scotchlocks.

Wish you were closer as I’d give you a hand.

 

[Banshee]

Well guys, I've had a right day of it today!!!!

I've been chasing wires front to back!!! Well back to front actually, I started at the bulbs and holders at the rear, both the side cluster stop lamps and upper stop lamp non functional

I traced the wires back as far as the rear left quarter and found atrocious scotch block bodge wiring that had been done by whoever had fitted the towbar :doh I just couldn't turn a blind eye to it as it was atrocious and I wouldn't have been surprised if it had have been responsible, but it wasn't!!! further down the car I went and followed the main route that the stop lamp wire followed ensuring no breaks or funny wiring along the way. I got to the passengers footwell and then round behind the dashboard to the drivers side and followed the wiring to the fusebox and down onto a harness that feeds the TCU

A couple of connections had some calcified white and green powder around them but these cleaned up nicely but I just still couldn't get the brake lights to come on even with the new brake pedal switches slaved in :doh

I then decided to run a live feed from the battery to the switch on the pedal and then a wire back to the feed to the 3 rear stop lights and hey presto depress and release the switch and the brake lights were working as expected :thumb2, great at least I can fix it temporarily for now.

I then decided that I would plug everything back in normally and tried to energise the relevant pins on the plug whilst it was plugged into the TCU and it had no effect at all so I suspect that the TCU is at fault. I'd like to temporarily test another one if anyone has one or even has one for sale?

This would kind of make sense as I have lost the option of having my interior lights switch on when you open any of the doors which I believe to be on the same plug as the stop lamps on the TCU and said cable does seem to be melted on the outside somewhat!!!!!

I've decided that I'm going to grab a Terrano and break it when I can claw a bit of cash in that I'm owed and break it for all of the bit's I'm currently looking for and then sell the engine and gearbox on and grab anything else of value inside such as stereo surrounds and rare electrical bits and interior clips that are becoming very difficult to get.

I'll not be doing anymore tonight now, the truck will be staying in bits tonight and I'll be wiring back up properly tomorrow morning in preparation to drive 4hours 27mins from my house to Maidstone to get a 2.8 6Cyclinder loaded into the back for the Patrol that's sat immobilised on the drive at the moment too

I hate electrical gremlins guys!!!!

 

[Banshee]

It's been a hell of a long and stressful day, if anyone with any electrical diagram reading knowledge wouldn't mind looking at the workshop manual for me and confirming that the brake lights are connected via the TCU but I'm pretty sure they were to be honest.

The red wire with black stripe and silver spots from the brake pedal switch runs straight from there to the TCU :nenau

 

[macabethiel]

TCU ?

Okay what does TCU stand for ? Control Unit?

I have heard of a SAM unit (Signal Acquisition Module) as named my Merc its really just a fuse box with relays.

 

[solarman216]

I am glad you asked that Ted, all I can think of is the Timer Control Unit and doubt if the brake lights come off of that, Rick

 

[solarman216]

Zac be careful if yours is a Bosch as it has two switches one for brake and one links to the ECU to cut fuel when the brake is pressed, do not know what would happen if you fed live back to the ECU on this, Rick

 

[macabethiel]

I am glad you asked that Ted, all I can think of is the Timer Control Unit and doubt if the brake lights come off of that, Rick

That sounds good if it fades out the interior lights etc.

 

[Banshee]

I am glad you asked that Ted, all I can think of is the Timer Control Unit and doubt if the brake lights come off of that, Rick

That's the one Rick, It seems it's responsible for a few things

Zac be careful if yours is a Bosch as it has two switches one for brake and one links to the ECU to cut fuel when the brake is pressed, do not know what would happen if you fed live back to the ECU on this, Rick

Haven't touched the 2nd one Rick, I wondered what it was for though :thumb2

That sounds good if it fades out the interior lights etc.

It's meant to do that but mine hasn't worked in forever and I really miss that feature to be honest :lol

 

[solarman216]

Confused, Rick

 

[Banshee]

Confused, Rick

What's confused your Rick? From what I can see there is a Red w/ black stripe and silver spotted wire and also Green w/ yellow striped wire to the brake pedal switch, the red one should be constant 12v feed from the TCU looking at the wires after tracing them back.

When the pedal is pushed the spring forces the switch to make contact and illuminates the brake lights. For some reason I'm not getting that 12v from the TCU to pedal switch, so I've ran a temporary for now.

 

[solarman216]

Well the TCU is a timer control unit for the interior cabin lights. I can see no connection to the brake lights, and if so what point? Rick

 

[macabethiel]

Weird wiring systems.

Well the TCU is a timer control unit for the interior cabin lights. I can see no connection to the brake lights, and if so what point? Rick

It might just be a wiring loom circuit loop thing, not sure on the Terrano but on quite a few vehicles I have owned the brake lights worked without the ignition being on.

In the past I have taken feeds off a Hazard Warning light switch to power stuff in the car that I wanted to be live without the ignition being on.

 

[Blocky10]

It might just be a wiring loom circuit loop thing, not sure on the Terrano but on quite a few vehicles I have owned the brake lights worked without the ignition being on.

In the past I have taken feeds off a Hazard Warning light switch to power stuff in the car that I wanted to be live without the ignition being on.

Yes, the brake lights do work without the key in the ignition.

 

[elty001]

Well the TCU is a timer control unit for the interior cabin lights. I can see no connection to the brake lights, and if so what point? Rick

I said exactly the same.It has no function for the brake lights but like Ted says the wiring could pass through the unit:nenau