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Re-wiring TR6


PaulAA

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Oh, and just keep things at the amusing end of the scale, I decided that removing the sub-dash panel and heater was too much faff, only to discover that bending a fully wrapped tail with all the thick battery connection cables through 90deg in a narrow space to get through the appropriate bulkhead hole was considerable, exponentially more of a faff.

Now it looks like this. Which is encouraging. Except that it means that I'm closer to the heart-stopping moment of connecting the battery and waiting for the puff of acrid white smoke...

IMG_8627.thumb.jpg.0147e20194fa776d8e80eed592d55bf9.jpg

 

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9 minutes ago, PaulAA said:

The old loom had two connections to the coil, one being the ballasted wire and the other coming from the starter relay. At the starter end of things, there was only an ignition connection and the direct battery cable. In the new loom, there is a signle cable from the coil, which appears to require connection to the starter. Only there's no visible connection point on the Powerlite hi-torque starter.

 

Yes, not so clear. In the old set-up, there were two connections to the starter motor - the battery and the ignition connections. The new loom requires a third connection, to the coil. It is the third connection point on the starter motor that I appear to be missing.

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Well, your coil/ballast resistor question has me puzzled too.

If it helps, the way it is meant to work is that you have one feed to the coil from the ignition switch which is live whenever the ignition is on. This goes via the ballast resistor, which could be the wire itself (and thus not at all obvious) or be a chunky ceramic resistor on a metal bracket, which is obvious. This provides a continuous reduced voltage.

In order to provide a higher voltage to the coil during cranking to give a stronger spark and aid starting, a second wire is provided that bypasses the ballast resistance. This is fed from the starter solenoid. 

I can see no reason for the third wire but I do wonder (though without being able to visualise the detail), whether it might be that your original loom had the integral ballast wire and the new one requires an external resistor, and the apparent extra connections are for this?

Feel free to prove me wrong…..

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There were different pick-off points for the ballast-bypass power feed to the coil, depending on the model year. Earlier cars with no starter relay took that power from the starter solenoid wire so that when power went to operate the starter it also fed to the coil.  Later cars took it from the starter relay which fed the other end of the starter solenoid wire, effectively doing the same thing.  

Sounds as though the new loom is for the earlier arrangement, so the extra wire is supposed to connect to the thinner white one in your photo.   

 

Edited by DeTRacted
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Thank you, chaps. This is becoming clearer.

I've asked Autosparks to clarify, but it appears that there is a boost/cold start connection drom the starter solenoid pole directly to the coil, but this will, presumably cut as soon as the key is released and returns to position II.

The harness doesn't contain any other connection to the coil, ballasted or unballasted.

angry.thumb.jpg.b262871176843261a117b0d85bc1ca7c.jpg

 

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  • 2 weeks later...

Well, this is fun. In a masochistic sort of way.

The wiring is nearly done and, so far, nothing has spontaneously combusted or failed to work on a permanent basis. The indicator switch, never a particularly reliable device, is wired with different coloured cable to the wiring diagram. Hey-ho. But then it started to shed the wires, so I took it pieces and the Lucas switch really is a shoddy bit of tat.

IMG_8770.jpg.d4f750cbba39009d9bca9cadcfb28cbd.jpg

Newly daubed in an irregular splatter of solder, it seems to work better.

The AutoSparks-made loom is a good fit and well made, but the coil connection is a little... odd. It has a semi-ballasted supply to the coil, linking an unfused main supply and the cold-start boost from the starter motor feed, so choosing between a 1.5 Ohm and 3.0 Ohm coil is a bit of a gamble. I haven't got the mother-of-all-diodes to enable the starter motor connection yet, so I've harvested the old full-legth ballasted cable from the barbecued loom (it emerged unscathed) and I'm gambling on using it ot connect the coil directly to the supply side of the fuse box.

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That indicator switch isn't great. I've had them spontaneously revert to a collection of springs and bits of plastic and metal inside the housing. 

Good work on the wiring. I laughed at your 'mother of all capacitors'. I have to admit that doing this job on a couple of occasions now I took the opportunity/easy way out and removed the whole ballast system entirely.

The early cars never had the ballast, it seemed to me to be something introduced by all the manufacturers during the 60s to cope with poorer maintenance from a widening car ownership. I decided that the simplest thing was to rely on a decent battery instead. Always worked fine for me.

Not original though so I can understand keeping the ballast.

Looking forward to seeing the car back on the road. 

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On 5/15/2023 at 10:48 AM, Escadrille Ecosse said:

That indicator switch isn't great. I've had them spontaneously revert to a collection of springs and bits of plastic and metal inside the housing. 

Good work on the wiring. I laughed at your 'mother of all capacitors'. I have to admit that doing this job on a couple of occasions now I took the opportunity/easy way out and removed the whole ballast system entirely.

The early cars never had the ballast, it seemed to me to be something introduced by all the manufacturers during the 60s to cope with poorer maintenance from a widening car ownership. I decided that the simplest thing was to rely on a decent battery instead. Always worked fine for me.

Not original though so I can understand keeping the ballast.

Looking forward to seeing the car back on the road. 

Thanks, Colin

I'm not really wedded to the 'keep it original' malarkay, especially where dangerous quantites of electricity and Lucas are involved. I rather prefer the concept of 'safe and moderately reliable'.  But... I have a 1.5 Ohm coil and a length of ballasted cable to hand, so I thought I might give that a bash first.

My worry is that the contents of the new loom, and hence the degree to which the cable is actually ballasted, are regarded as something akin to a state secret by the manufacturer and I'm also a little uneasy that a direct cable connection (be it ballasted or not) from the fusebox to the coil is a bit too... easy. Got to be a flaw in my logic somewhere... So I'll probably have to spend a little more time prevaricating.

But on the basis that the TR sits in a comfy underground garage (on a bed of feather pillows and tended by vestal virgins) and is not exposed to real cold, I think I'm going to forego the cold start wire from the starter motor.

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  • 2 weeks later...

The longest-ever loom installation continues apace.

I did, however, make an interesting discovery this evening. I failed to disconnect the battery and, whilst fiddling with the tacho gauge, the exposed end of the tacho drive came into contact with the braided oil pressure pipe some PO fitted in the dim and distant and... BANG! there were sparks. I multimetered the braided pipe and, of course, the damn thing is a conduit to earth.

This pipe is too long and flops about under the dash, so now I'm wondering if this might have been the source of my loom-incinerating short...

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It is, John - I checked!

I can understand how applying a power source in circuit between the braided pipe and the tacho drive would register a current on the multimeter, but why would either the braided pipe or the tacho drive be live in the first place..?

I'm away for the weekend, so it is a mystery whose denouement will have to wait until next week's episode. In the meantime, the battery is very definitely disconnected.

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Um….:blink:

I can see that the braided sheath on the oil pressure gauge capillary tube would be a good earth - it’s attached to the engine block, which is well earthed. The same goes for the Tacho drive though. 
 

Why or even how either would be live escapes me though.  Paul did you determine which one of the two was actually live?

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1 hour ago, Nick Jones said:

Paul did you determine which one of the two was actually live?

I haven't yet, Nick. I've had my garage pass suspended until Monday, so I'll check when we return from the coast.

Our place by the sea is 10km from the Kaliningrad border, and I keep hoping that, when we go for a walk to the border, we'll see somebody I can stick two fingers up at through the wire fence. Maintaining those small moments of entertainment...

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Paul,

You remind me of a famous music hall 'recititation', "Albert and the Lion" 

Mr.& Mrs Ramsbottom with their son, Albert, are at the Zoo, view the lions' cage:

So straightway the brave little feller,
Not showing a morsel of fear,
Took his stick with its 'orse's 'ead 'andle
And pushed it in Wallace's ear.

You could see that the Lion didn't like it,
For giving a kind of a roll,
He pulled Albert inside the cage with 'im,
And swallowed the little lad 'ole.

It didn't end well for t'lad.

I would suggest that this sage advice applies to Bears as well as Lions.  But Poles are ever quixotically courageous!

John

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I'd forgotten that one, John. 'Tis a sad reflection of our cultural evolution that the only metaphor that sprang to my mind was:

Flicking tiger balls Blank Template - Imgflip

And indeed, the world is strewn with the principled foolhardiness of my (new) countrymen...

Paul

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18 hours ago, PaulAA said:

This pipe is too long and flops about under the dash, so now I'm wondering if this might have been the source of my loom-incinerating short...

I fitted a braided oil pressure line to my Spitfire and had the same concern about it flapping around behind the dash, so sleeved most of its length with heat-shrink. 

3 hours ago, PaulAA said:

In the meantime, the battery is very definitely disconnected

Sensible! I can't see how the tacho cable and oil pressure line could be at different voltages if they're both connected to the engine...?!

Keenly anticipating the next instalment.

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Back on the case, garage pass restored and heat shrink acquired.

And the job is (almost) done. Nothing has burst into flames yet. Things seem to work as they ought. I still have to:

- rig up the steering earth that disappeared when a substitute steering rack was installed

- jury-rig a ballasted supply to the coil to by-pass the inventive version included with the loom

- establish why the oil pressure light STILL doesn't work (new bulb installed... but I suspect my ad hoc wiring to the three-pronged oil sensor isn't working and I might have to cough up for a new one)

Sorted. Until it turns out that it isn't, of course.

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1 hour ago, Nick Jones said:

Three pronged oil pressure switch??!

Eh? Is this a US market thing? Probably easiest to get a conventional single pronged one?

Yeah. Looking at those wiring diagrams it seems it is. Unfortunately.

Those three prong switches are pants. I had one on the RV8 in the Scimitar initially as that's what was fitted in the SD1. The first one actually failed by blowing the cap off and dumping a very large proportion of the sump contents therough the resulting hole in the oil system. Decent replacements became increasingly difficult to obtain. So in the end I got rid of it and went with the single pronge version instead.

If it was me I would revert to the earlier TR6 wiring arrangement that used the single prong switch for cars before the anti run-on valve was fitted to cope with the anti-smog gear.

I would suggest that if you have/want to keep the anti run-on valve then there are better ways of operating it than the oil pressure :blink:

Edited by Escadrille Ecosse
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47 minutes ago, Escadrille Ecosse said:

Yeah. Looking at those wiring diagrams it seems it is. Unfortunately.

Those three prong switches are pants. I had one on the RV8 in the Scimitar initially as that's what was fitted in the SD1. The first one actually failed by blowing the cap off and dumping a very large proportion of the sump contents therough the resulting hole in the oil system. Decent replacements became increasingly difficult to obtain. So in the end I got rid of it and went with the single pronge version instead.

If it was me I would revert to the earlier TR6 wiring arrangement that used the single prong switch for cars before the anti run-on valve was fitted to cope with the anti-smog gear.

I would suggest that if you have/want to keep the anti run-on valve then there are better ways of operating it than the oil pressure :blink:

They are indeed pants. This is the second one during my tenure. And the last. The anti run-on valve, all the EGR pipes and wizz-bangs and the safety belt nanny system have progressively graced the bottom of the bin over the years and the car is a good 10kg lighter.

To reach my inner schoolboy, the only bit of the emissions system that tickles me is the bit at the end of the exhaust pipe, to see how many car alarms I can trigger starting up in the underground parking at home.

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Another day, another bit of confusion.

A (French) single-pronged oil pressure sensor arrived this afternoon and is now adorning the left side of the engine block. Connections duly made, battery connected, key turned and... (i) no oil pressure light and (ii) the brake failure light was illuminated and remained so when the engined fired up (oh dear, the word 'fire' still makes me quiver...). So I tried different combinations of disconnection and found that removing the cable to the brass brake failure switch achieved the desired result: brake warning light and oil pressure light come on when the key is turned and go off when the engine fires up. So, the brake failure light is buggered.

However... the oil pressure light has the intensity of a candle seen at a mile distant through heavy fog, whilst the brake warning light is slightly brighter than a small thermo-nuclear fireball. Shurely shome dishtake - it's meant to be the other way round, isn't it?

I can see why the circuit works with the brake failure cable disconnected, but why would it not work with it connected..?

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Tomorrow, I shall be addressing the incontinent rear left brake slave cylinder. With a hammer. Once again, there was a lot of DOT4 to scrape off the garage floor yesterday.

Paul

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1 hour ago, PaulAA said:

... the brake failure light switch is buggered...

Oh splendid....

But that answers your relative brightness question. With the brake failure switch failed closed its bulb sees the full 12V drop while the oil light only get the voltage 'left over' after its supply goes through the brake warning bulb.

Hopefully you can get the brake switch and it doesn't require the system to be drained of fluid to change.

Edited by Escadrille Ecosse
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Thanks, Colin.

Sometimes the light dawneth slowly... The content of the rear brake circuit has spread itself lavishly across the garage floor, so the brake switch ought to be registering a fault...

I'll report back when brakes and brain have been repaired.

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