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Intermittent short on brake light circuit


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I seem to have an intermittent fault on the brake light circuit on my 1994 Defender 110 station wagon (300tdi). It started off as one brake light not working, dead incoming supply, and it turned out someone had replaced the connection from the switch in speaker wire :blink: I reconnected the old circuit and all seemed OK. This was in between another project (TD5 instrument panel) where I'd managed to blow fuse 1 (20A - Aux, horn, interior light, flash) by connecting the clock up wrong. After putting it right and replacing the fuse, I noticed the brake lights would flicker on and off on their own, and it stopped doing this when fuse 1 was pulled.

At the moment I'm running without fuse 1 in, and the brake lights are fine, but obviously I have no horn, flasher, clock, etc. Rather than run a new brake light circuit, I would prefer to repair the fault so it doesn't cause other problems later on. My usual method of clearing faults won't work here (keep putting bigger fuses in until it blows clear :lol:) Does anyone have any suggestions of where I should look for the fault, i.e. where the two circuits run together, before I attempt to dismantle the whole dashboard or something like that.

Thanks in advance

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  • 5 months later...

Finally found it yesterday! Have been running with Fuse 1 out and living without horn, flash and fog lights for a while, but while doing something else by the rear crossmember I saw a big green lump just where it exits the chassis, when I unwrapped the many layers of tape, I found 13 red straight joint crimps, lots of green crumbly nastiness, and lots of potential for shorting out. I suspect whoever changed the rear crossmember previously went for the easy way out and chopped it then jointed back up and hoped for the best...

th_2014-03-08180335_zpseca0fcd5.jpg

The problem now is, I don't think there is enough cable to get on to do a decent joint between the fault and where it enters the chassis. My plan at the moment is to hopefully withdraw the loom from the chassis, re joint the cables and insert pieces if need be to replace the dodgy bits, and run the loom outside of the chassis in some split conduit (of which I have lots). Once it's out of the chassis I'll open it up and check for damage etc before joining, rewrapping, and putting it in the conduit.

Couple of questions regarding this, where does the loom enter the chassis up front? Are there any other exit points, or is it just front to back? I suspect the easiest way to remove it will be to pull it out of the front, as there's no problem chopping it at the back where my big problem is....

P.s. I'd love to go and buy a whole new loom, but they are a bit expensive for me if I can make this repair work first...

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enters at the right hand side main rail inner face below bulkhead, disconnect all the chassis to bulkhead connectors, cut the big grommet off, then feed loom into chassis & carefully extract the loom from the rear end,, I found this way much easier than disconnecting all the rear end connections.

a new chassis loom isn't that bad, I've got a new one from Autosparks for my 110 waiting to be fitted when the summer gets here

just make sure you select the correct item in the drop list

http://www.autosparks.co.uk/product_info.php?products_id=2009

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Decided to go out and play tonight, as the duff connections were just outside the grommet at the back of the chassis I chopped it and pulled it all through the front, didn't bother disconnecting it from the bulkhead. Didn't have to go back too far to get non crumbly green cable, about an inch or so. Prepared the ends ready for jointing to the other end with some proper solder containing lead, sorted out a small bit of chafing, wrapped the lot in vinyl mastic tape and then stuffed it into split flexible conduit.

Out of interest, what is the wire coming out of the loom just before it enters the chassis by the bulkhead, plugging into a sensor on the gearbox? This is on a 1994 110 200tdi station wagon (not 300tdi as I said before) My end goal is to track down the reverse switch wiring as I'm putting a reversing camera in, but as it's just one wire I don't think I'm that lucky!

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Out of interest, what is the wire coming out of the loom just before it enters the chassis by the bulkhead, plugging into a sensor on the gearbox?

that wire would be the blacl with blue trace for the difflock switch

This is on a 1994 110 200tdi station wagon (not 300tdi as I said before) My end goal is to track down the reverse switch wiring as I'm putting a reversing camera in, but as it's just one wire I don't think I'm that lucky!

reverse light wires are green with a brown trace, easier to connect a camera into the circuit at the rear end, behind the rubber flap in rear of the wheel arch or in the right rear corner behind the metal cover protecting the rear lights wiring

as you mentioned a reversing camera have a read of this thread, a few of us on here have fitted one.

http://forums.lr4x4.com/index.php?showtopic=78855&hl=

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