Ignition stays on and melted brown wire to headlight switch

[stuart]

1 hour ago, BaulyCars said:

I'm pulling the dash to get eyes on the loom, see whether the brown has made a mess throughout - that brown seems only to run through one branch of the loom. 

Shame to swap the loom out as its practically new.     

Safety first, if its melted there it will have done damage somewhere else, unless you fancy pulling the whole loom and stripping the insulation from the whole thing then it can never be trusted again. Dont forget the loom is in two halves anyway and there is a joiner by the left hand "A" post so it maybe only the front half damaged.

Stuart.

[BaulyCars]

All the TR’s I’ve looked at so far have had a chewed up loom - starting to think they need to be swapped out with every oil change

Thanks, Stuart. 

Good that it’s in two halves, and I see one can buy the main or body sections separately. 

 

Edited December 18, 2023 by BaulyCars

[BaulyCars]

1 hour ago, Jonny TR6 said:

Can you get an endoscope/phone camera on the back of the mounting point to see if there's a contact point ? Every time I've earthed a screwdriver in the house when working live there's an arc and the screwdriver virtually welds itself to whatever I've earthed against, leaving a tell tale mark.

 

Have had a look, and back of the centre switch console is clean, no burns/marks.

 

 

[RogerH]

I've often thought that it would be a good idea to have this Brown power wire left out of the loom and have it running in a plastic or insulated steel  tube.

 

Roger

[stuart]

42 minutes ago, BaulyCars said:

All the TR’s I’ve looked at so far have had a chewed up loom - starting to think they need to be swapped out with every oil change

Thanks, Stuart. 

Good that it’s in two halves, and I see one can buy the main or body sections separately. 

 

If they have then you can guarantee that at sometime or other someone has added/bodged some extra cables in for various things over the years, quite often because they havent maintained the earth points correctly and its been an attempt to try and get something working again.

Stuart.

[BaulyCars]

36 minutes ago, RogerH said:

I've often thought that it would be a good idea to have this Brown power wire left out of the loom and have it running in a plastic or insulated steel  tube.

 

Roger

Good idea - is there some type of heat-shrink wrap it could run in?

Maybe with an in-line fuse of sorts too?   

[Jonny TR6]

9 minutes ago, BaulyCars said:

Good idea - is there some type of heat-shrink wrap it could run in?

Maybe with an in-line fuse of sorts too?   

Convoluted tube is your friend here Toby ! got miles of it on my split and it comes either split or solid to aid fitting.

[RobH]

1 hour ago, BaulyCars said:

Have had a look, and back of the centre switch console is clean, no burns/marks.

... which maybe points to a short to case inside the switch.....

As for in-line fuses, there should be an unused fuse on the existing block that you could utilise - or even fit a larger block with more ways. 

[RogerH]

Hi Toby,

I believe Triumph didn't fit a fuse for the headlights as they did not have a particularly good reliability record at the time.

If installed and maintained properly the headlight wiring was quite safe.

Now a days fuses tend to be far better.  However for the rest of the car one can fuse all the littler sub-circuits - no need for a 35amp fuse for a small circuit.

 

Roger

[BaulyCars]

1 hour ago, stuart said:

If they have then you can guarantee that at sometime or other someone has added/bodged some extra cables in for various things over the years, quite often because they havent maintained the earth points correctly and its been an attempt to try and get something working again.

Stuart.

Yeah this - and usually bodges that I can't work out what they do.  

[BaulyCars]

23 minutes ago, Jonny TR6 said:

Convoluted tube is your friend here Toby ! got miles of it on my split and it comes either split or solid to aid fitting.

Can you get quite small diameters (so for a single wire say)?

[BaulyCars]

17 minutes ago, RobH said:

... which maybe points to a short to case inside the switch.....

As for in-line fuses, there should be an unused fuse on the existing block that you could utilise - or even fit a larger block with more ways. 

Won't risk using that switch again - will suggest to owner to revert to the dash rocker type.

 

17 minutes ago, RogerH said:

Hi Toby,

I believe Triumph didn't fit a fuse for the headlights as they did not have a particularly good reliability record at the time.

If installed and maintained properly the headlight wiring was quite safe.

Now a days fuses tend to be far better.  However for the rest of the car one can fuse all the littler sub-circuits - no need for a 35amp fuse for a small circuit.

 

Roger

Makes sense. 

I guess the fundamentals of bringing 12v into the car to the switches is the root problem anyway. 

The whole loom/relays/fuses (or a modern fuse-less PDM unit) could be a nice future project.

Getting off topic - I still haven't found my short

Oo, and I just worked out you can reply to two quotes in one post, apologies for the multiple replies above!   

[keith1948]

Looking at the wiring diagram I can't see a relay for the headlamp circuit. All the power goes through the switch and this seems to be a weak point. I fitted a Moss headlamp relay kit and the relays have their own fuses. I did this years ago after a friend had a similar meltdown in his TR6. The brown power cables to the headlamps are not in a loom but readily visible in the engine bay as are the relays and fuses.

Maybe the problem with your car could be a bad earth somewhere so the power tries to find an alternative pathway. I've had this a couple of times with some strange results such as horn trying to earth through main beam circuit. No idea why. Might explain your ignition mystery.

Good luck

Keith

[PodOne]

Given the loom is likely to be toasted in various place you cant see (mine was) and to fix you will have to unwrap it why not just use it as a pattern and make your own using relays/fuses in every circuit. I'm no expert and managed it with some help from Rob and others. Saved a packet and have a better loom going forward.

Andy

[Jonny TR6]

4 hours ago, BaulyCars said:

Can you get quite small diameters (so for a single wire say)?

https://www.ebay.co.uk/itm/115525119764?hash=item1ae5d56f14:g:RWgAAOSwmfZketYs&amdata=enc%3AAQAIAAAAwE2%2FHI1fVxn05OwOWtB1VyUi2OqxDgZhyjywO81b86Qrx97imvoeg4V07Z%2BuBPgMbHphrg79cKu9WT46YWFxWbBE92dBIVLQPItUMEKe3VkqbIcx11t9RCopI%2B1GFuIs757ZAkVAYWuNoebovvMIl8wlo9KoYi9xsKWB1IZu4vmoL9HvL15nqOno%2FwRxy45IHKiUWCW816XIKt5KllisL04yH6p4GFerqLOVgsfIRfXyCDBzBvVDp2CbUeXZj9AOvw%3D%3D|tkp%3ABlBMUPLLsOyPYw
 

Looks like 6.5mm is the thinnest bore, but will protect a single cable going through a bulkhead etc much better than heat shrink.

[Mike C]

I'd disconnect the ends of the brown wire and find out where it's earthing with a multimeter.

Some earthing points may be due to burnt insulation but one earthing point probably caused the original  fault.