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Re-wiring TR6


PaulAA

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I blew an in-line fuse a couple of days ago and started dismantling the kidney panels either side of the centre console and BLEUCHHH - out poured the spaghetti of wires I'd feared were luring there every time I've had the dash out.  I'd suspected that the wiring was a little different to the '75 wiring diagram, and deeper investigation suggests that there is very little in accordance with the wiring colour and routing scheme.  Some vaguely useful stuff, like the indicator and ignition lamps, choose not to work at all.

So, I can foresee what the main winter project will be at the end of the season.  I want to remove some of the unnecessary US-market stuff (seat belt warning daisy wheel, fairground array of non-working warning lights, etc) and add relays for headlamps, flasher and a separate circuit for a 12v auxiliary socket.  This suggests that there will be more wiring than I want/need in a std US-market harness and I will need to add circuits for relays, etc.

I doubt I will have time/patience/competence to build my own harness, so the question is whether anybody can suggest a source for customised LHD looms at a reasonable price.

Paul

 

Edit: I do, of course mean a reasonable price for the harness, not the advice, which will undoubtedly be priceless :biggrin:

Edited by PaulAA
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There are companies that sell 'one size fit's all' harnesses e.g. https://www.painlessperformance.com  I've no experience with them personally, but they come wired with relays, fuse boxes etc and it's pretty much trim to size.  You can find them and others on ebay too.

I've done a few looms, including my Spit and I'd say the planning takes the longest.  If you've got all the kit and all the bits you need it's not all that time consuming.  However, I studied electronics so have a kind of head start when it comes to debugging faults.  I guess the Spit took maximum a couple of days from picking up the first reel of wire, laying out the loom, tying and wrapping it, installing it then fitting connectors and plugging it all in, that said, it's very minimalist as it's a race car (I did use original lucas coloured thinwall cable for everything though, like a nerd).  The other advantage is that you get to make your own wiring diagrams and you know how it's all done, so in theory you can fix it easier...

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Thanks, Chaps

21 hours ago, Nick Jones said:

In what way does it need to be custom?

Nick, just to avoid having to find secure homes for all the unnecessary cables and connections included in the late US harness and make sure the aux and relay circuits are wrapped into the harness.  Think of it as slightly anal fastidiousness.

Paul

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Paul,

It's extra work, but done while you are alreday sweating over the loom, to add multiway connectors behind every electrical item.   You will have noticed that this is usual practice on moderns.      It makes future work on any item much easier.  No scrabbling in the dark, behind the dash, plugging several Lucar connectors into the back of a gauge, and getting it right.  Just one connector, that can only go togther one way.

Many suppliers of such connectors.   I use Vehicle Wiring Products, weatherproof  where indicated: http://www.vehicle-wiring-products.eu/section.php/117/1/multi-connectors

John

O.jpg

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I'd recommend superseal/econoseal connectors (and of course, a half decent crimper). They can be a bit fiddly until you get the hang of them, so get a few more than you need...  But, they're cheap, durable and waterproof and I find them easier to connect/disconnect than the white lego block multiways - still, either are much easier to deal with than bunches of bullets/spade terminals.

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I have just fitted an Autosparks wiring loom to my GT6, and must admit found the job easier than I thought. Biggest issue was not having enough time to do the job in long sessions of time, but a few hours here and there, therefore time was lost re-caping what I had done, maybe being middle aged did not help!

 

Autosparks will add extra circuits for items like electric fans, additional lighting etc. Their looms are not cheap, but very well worth it.

The following may help:

1. Make notes copied from a Stanpart manual's wiring diagram, a copy of the relevant wiring diagram is essential.

2. When taking out the old loom, cut wires a couple of inches before the electrical item to act as a visual code. A mate of mine suggested that I do not this after I fitted my loom, really good idea that I wish I had done.

3. Replace items like relays, flasher units etc for more modern types if originality is not required.

4. Change the fuse box for a more modern blade type unit.

5. Do the job in sections and work logically.

6. If sticking with bullets and connectors, replace the black single or double connectors for new. Buy a crimping tool and back up by soldering.

7. Denote sections of the loom with cable ties that have small tags.

8. Carry out the job in an area with space around the car. Also, a few trips to the gym before starting work to attempt to be totally flexible would help...grovelling around under a dashboard is both horrendous and painful!

9. Ensure you have plenty of light!

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Tim,

All good advice, save for the last phrase in Item 6.    Crimping was developed for aerospace, because solder 'wicks' up between the strands, leading to a rigid section just before the connector, in what should be a flexible cable.     Vibration can cause this to break.     

How to crimp well?  See the Molex webpage: https://www.molex.com/tnotes/crimp.html

Buy a good crimping tool!  I used to solder, then crimp AND solder, but since I bought a proper crimp, I have used no other means to make up connections.

John

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I agree, as do NASA https://nepp.nasa.gov/files/27631/NSTD87394A.pdf :)

Quote

Crimping. Stranded wire shall be used for crimping. Crimping of solid wire is prohibited. Crimping of solder tinned stranded wire is prohibited.

It's actually a useful document, it covers everything you need to know about strain relief, knot tying and the correct way to splice wires etc.  That said, plenty of people do solder connectors,  Andy V used to IIRC.  Personally I wouldn't recommend it, for the same reasons but also that it makes replacing connectors harder..

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  • 3 years later...

Evening, chaps

So, three years down the line and the loom is still not changed. Anybody else hereabouts familiar with the principle of terminal prevarication? I've made some progress sorting out the current loom, which increasingly appears to be serviceable and careful pruning of the US bloat has resulted in less spaghetti behind the dash.

However, I have a problem I can't fathom. The oil pressure warning light doesn't work. In the 1975 CF, the brake pressure warning light is in line with the oil pressure light and both are meant to light up with the ignition at 'II'. Both the oil pressure switch on the engine block and the fluid pressure switch on the brake H splitter are relatively new, but I have:
- the brake warning light permanently illuminated (a new phenomenon, resulting from replacing the previously blown bulb), which only turns off if I disconnect the power feed to the switch on the H splitter (but not the earth)
 - no detectable current at the oil pressure lamp holder with the ignition at 'II'

The anti run-on valve is long dead and now removed, so the third connector on the oil pressure switch is redundant, but I don't see this impacting on the fucntion of the oil pressure warning light. Witing to the oil pressure switch is checked and confirmed.

So the two worries are:
- why is there no juice at the oil pressure warning lamp holder?
- why IS there juice at the brake pressure warning lamp, given that the circuit relies on the oil pressure lamp.tr2506(1)-8.thumb.jpg.f5a06cf77b7e47b52c054961f47e4af7.jpg

Any help/pointers deeply appreciated

Paul

 

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Unless I have misunderstood your description it sounds as though the brake failure switch (PDWA) is permanently made. 

Supply comes on the white wire so that in the absence of oil pressure, both lamps are in series and earthed via the oil pressure switch. The brake failure switch is normally open in the absence of a fault, allowing both lamps to light, though at reduced voltage, in position ll .  That is a safety measure as it shows the lamps are working before you start the engine. 

The brake failure switch is operated by a shuttle with pressure from each half of the brake circuit on opposite ends. Loss of pressure in one half of the split circuit allows pressure in the remaining half to push the shuttle away from the centre so closing the switch. Once operated, it stays there. 

I understand the shuttle can be moved back to the centre by removing the switch assembly from the body and using a thin probe.

 

 

Edited by DeTRacted
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Good to see you are alive Paul, and also that you are still persisting with Triumphs. Hope life is being kind(er) to you?

reading in Australia on my phone so your diagram is a bit small….. so happily Rob has already answered the question and I can’t see anything to argue about. Just to add that the PDWA valve being over one way doesn’t necessarily mean a current fault with the brakes as the shuttle position has to be manually reset any time a pressure imbalance has moved it over - which could even simply be the result of bleeding the system.

If you can reset the shuttle position and prove the electrics, and it continues to work after stomping on the brakes, all is good. If the balance light comes back on after stomping on the brakes then a brake fault would be implied. Hopefully this doesn’t happen!

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Morning, chaps, and thank you for the feedback, but no dice.

I removed the PDWA switch and the bobbin valve appears to be in the right position - I also measured the depth to the bobbin contact surface and it corresponded with the extended switch actuator length. The bobbin itself appears to be metal, not plastic.

Theoretically, the switch could therefore be earthing through the metal bobbin, but I reconnected the dismounted switch and ran the engine, as a control, and the brake warning light remains illuminated.

So, given that the light goes out when the power is disconnected, and not the earth, could the issue be a faulty PDWA switch?

Presumably, this is independent of the oil pressure warning light issue...

Thanks, Nick, on the mend and very much a member of the cult!

Paul

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I guess the oil pressure lamp is lit in position ll when you had the wire pulled from the switch Paul?  If so the switch is either stuck closed or somehow earthing through the actuating pin as you say.   If the switch is closed it prevents the oil pressure lamp from lighting as it earths out the supply which would otherwise come from the brake warning lamp. 

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1 hour ago, PaulAA said:

given that the light goes out when the power is disconnected, and not the earth, could the issue be a faulty PDWA switch?

Presumably, this is independent of the oil pressure warning light issue...

This suggests that the circuit is earthing somewhere it shouldn't, between the brake warning lamp and the oil warning lamp.

How is it actually connected up? I'd guess the black & purple feed to the oil light is coming directly off the brake warning light.. or maybe the PDWA switch? 

Edit: ignore my muddled rambling, Rob's post above is more useful

Edited by PeteStupps
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Thanks, Rob & Pete. The wiring colour is (unusually) exactly per the diagram above.

I've just pulled the PDWA switch and checked it with the multimeter, just to eliminate it from our enquiries. Current flows in both the open and closed positions, but not from the activator, so I think the culprit for the constant brake failure light is identified. Now for the oil pressure warning light...

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6 hours ago, PaulAA said:

Now for the oil pressure warning light...

Paul - as Rob says above, if the PDWA switch is closed / earthed, that will prevent the oil light from working. If you pull the cable off the PDWA switch the oil warning lamp should function. 

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  • 2 weeks later...
  • 1 month later...

Chaps

Just to close this topic, I decided that, if the brakes failed, a natty light appearing on the dashboard might be a tad too late, so decided to omit it. Given that the light is in series with the oil pressure light, it should be sufficient to omit the light and provide power directly to the oil pressure light (white cable in the diagram back up the thread), with the circuit broken by the oil pressure swithc on the block. Job done, and the oil pressure light shone sweetly and, as required, turned off when the engine caught.

All was good for twenty minutes of serene pottering through town. Then, half way across a fancy suspension bridge over the river, a plume of white smoke billowed atmospherically from under the dash and, indeed, the power cable between the voltage meter and the oil pressure light was toast. Given that the circuit was not closed and the light was not on, there must be a short... somewhere.

New Year's new hunt.

Paul

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