Electrical Fault 1989 Defender

Evening all,
I'm new to Land Rover ownership and already have my first headache, so would be grateful for any advice on the following...
I have a 1989 Defender 90, with a 300tdi engine. Everything was working fine until last weekend. I woke up to find the brake lights stuck on. (Happened sometime in the night)
I disconnected the battery as a quick fix. I have since disconnected the brake switch but the lights are still staying on.
The only way I can isolate the fault is by removing the first fuse which is my permanent live and controls my radio, clock, interior light, etc. I can then turn the key in the ignition and get the break lights working properly.
I have disconnected the radio and removed the rear break lights and the fault remains, before I dismantle the dash does anyone have any advice as to where the short could be or where I should be looking.
Thanks in advance

Do you have a tow socket by chance?

Oh and welcome.

Time to get the DMM out and check why you have power to the circuit all the time,
Do you have a wiring dia cos you are gonna need it. Ignition switch maybe a good place to start.

J

Check the bulbs, then check the looms where it enters the chassis at the front and where it exits at the rear.
I think the only permanent live to the rear is the purple wire.

marjon said:

Do you have a tow socket by chance?

Oh and welcome.

Time to get the DMM out and check why you have power to the circuit all the time,
Do you have a wiring dia cos you are gonna need it. Ignition switch maybe a good place to start.

J

Click to expand...

Morning, thanks for the reply.

I do have a tow socket, but I've disconnected the brake lights from this and the problem is still there. I've been working from the Haynes manual wiring diagram but this seems to differ from my Landy a little bit. This morning I've disconnected the GP cable from the push connectors in the rear light and tested this on its own and getting about 10v, (its still disconnected from the brake switch under the bonnet)
I think I will remove the dash so I can get at the wiring from the fuses a bit easier and take a look at the ignition switch

Thanks for the advice

lynall said:

Check the bulbs, then check the looms where it enters the chassis at the front and where it exits at the rear.
I think the only permanent live to the rear is the purple wire.

Click to expand...

Thanks for the advice, the loom looks ok where it exits at the rear and at the front, I have also checked where it comes up into the rear of the truck. I have found the purple wire and this isn't connected at the rear and looks to be undamaged.

I haven't changed the bulbs and they've been working fine up until this point. I'm just a little thrown that its happened overnight and not whist I've been driving or had the Landy running.

I'm thinking of dismantling the dash and going from there, it will give me an excuse to wire the front and rear heated windows and the heated seats the previous owner never got round to doing.

as marjon enquired do you have a trailer socket to eliminate water ingress and a back feed on this item ,if you have removed the brake switch this eliminates
the feed to the brake lights ,I would advise checking the bulb and bulb holder and disconnect the rear connector before ripping the dash apart

UJU said:

Morning, thanks for the reply.

I do have a tow socket, but I've disconnected the brake lights from this and the problem is still there. I've been working from the Haynes manual wiring diagram but this seems to differ from my Landy a little bit. This morning I've disconnected the GP cable from the push connectors in the rear light and tested this on its own and getting about 10v, (its still disconnected from the brake switch under the bonnet)
I think I will remove the dash so I can get at the wiring from the fuses a bit easier and take a look at the ignition switch

Thanks for the advice

Click to expand...

Funnily enough I would start with the earths at the back then under the bonnet. then check the back of your fuse box for melting/corrosion.
You have a short of some sort of short leading to a leakage of volts, the earth on the brake light is its easiest path, if you looked at it at night are any other lights glowing a bit.

One of the biggest problems with 1 this age, is age, and previous owners bodges work.

Do a search on tinternet and you will find free elec dia. Or our resident supplier of fantastic dias may be along soon @mystery to help you.

It will be something simple just may not be easy to find.

J

Edit and as if by magic he turns up while I was typing

UJU said:

Thanks for the advice, the loom looks ok where it exits at the rear and at the front, I have also checked where it comes up into the rear of the truck. I have found the purple wire and this isn't connected at the rear and looks to be undamaged.

I haven't changed the bulbs and they've been working fine up until this point. I'm just a little thrown that its happened overnight and not whist I've been driving or had the Landy running.

I'm thinking of dismantling the dash and going from there, it will give me an excuse to wire the front and rear heated windows and the heated seats the previous owner never got round to doing.

Click to expand...

Yes the purple wire is not connected at the rear of the truck, but I think it is still live, maybe disconnect it in the fuse board and see if that clears your fault, that way you then know it is a loom issue.
Has the car had any chassis welding repairs done?
As for the main loom I would cut back some of the outer tape to check the wires inside, do not go on just outer tape looks alone, the rear routing is very difficult for the cables with sharp turns and edges all over the place.

lynall said:

Yes the purple wire is not connected at the rear of the truck, but I think it is still live, maybe disconnect it in the fuse board and see if that clears your fault, that way you then know it is a loom issue.
Has the car had any chassis welding repairs done?
As for the main loom I would cut back some of the outer tape to check the wires inside, do not go on just outer tape looks alone, the rear routing is very difficult for the cables with sharp turns and edges all over the place.

Click to expand...

The car had a new galvanised chassis about 4 years ago
Disconnecting the purple wire makes sense, that Green and Purple wire is still showing voltage with nothing connected either end so it does sound like a loom issue unfortunately. Il cut back some of the tape where it enters and exits the chassis

Thanks for the pointers

UJU said:

The car had a new galvanised chassis about 4 years ago
Disconnecting the purple wire makes sense, that Green and Purple wire is still showing voltage with nothing connected either end so it does sound like a loom issue unfortunately. Il cut back some of the tape where it enters and exits the chassis

Thanks for the pointers

Click to expand...

Could also be sharp edges/mig wire stuck in the wrong place damaging the loom.
90 and 110 have the same length loom, the extra wiring on the 90 is just hidden in the chassis, so if you have a 90 you can pull a good length out the front to check, then pull it out the rear to check that as well, pulling the rear out will also pull the front back in, should be big fat grommets where loom enters the chassis.