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MG Midget and Sprite Technical - Ancient Loom Colours

Can anybody remember seeing an original loom in all its glory? I'm re-using mine, and the wires are woven fabric sheath over plastic. So far all the plastic has been black, and the sheaths are generally beige. If I clean them up, I sometimes get a hint of colour, but the cleaning up might just take that off as well. I see from my dismantling notebook that the offside rear lights are served by pink and beige, while the nearside is salmon and beige.
I think these should be red and green/purple.

Back to the question:- were these fabric sheaths brightly coloured in the last century? I haven't delved further into the loom yet - where they will have been better protected - but I shall.
Nick and Cherry Scoop

Hi Nick

When I stripped off the covering for the boot section I found the fabric wiring was still quite colourful! The section under the bonnet and to the sidelights was a uniform beige

I found re-using the original loom a bit of a false economy as the system developed all sorts of failures.
A new loom from Autosparks was great and fitted well. They also modified the loom to accommodate an additional wire to the electric fuel pump. All the fabric colours were proudly displayed and lights were noticeably brighter as well. I did reuse some of the original instrument light fittings as the replacement stuff did not look so robust.
Bob Beaumont

Thanks Bob. When yours started to go wrong, how much repair work did you do before you took the plunge and bought a new one?

New loom is such an off-the-road sort of job.
Nick and Cherry Scoop

Well mine was in a bit of a sorry state to start with. The fabric binding all the wires together had rotten in places and needed taping together again. I then found after I re-installed it that there were loads od earth issues which too ages to sort. The other problem was that the wire had become quite corroded in places and needed renewal, the inner plastic core had become brittle and soldering in new bits meant removing quite a section of wiring. In the end I just decided the faff was not worth it. As the shell was bare it was easy to thread the new loom in and I completed it over a weekend.
Bob Beaumont

Oh OK - so you weren't on the road. Nor am I, so I will look carefully along it, and do some continuity testing.
Nick and Cherry Scoop

What route does the rear loom take to the front?

I had assumed that after looping over the off-side rear wheel arch it then appears through the bottom opening of the B post just above the inner sill. From there it goes forward beside the sill to pass under the door opening before rearing up the inner face of the A post to reach the big grommet hole through the bulkhead. That's how I have routed mine because that is how I did it on the '71 car. But there is nothing to say it was correct then either as that car was equally a basket case with no loom when I got it.

The bit that is "uncomfortable" is having the fat cable beneath the door opening where it prevents the trim panel from fixing flat to the sill. I partly got around that on the later car by using a length of ribbon cable that I got from a scrapyard Citroen. The ribbon has the wires laid flat, side by side rather than bound into a round fat bundle which is neater to fix to the face of the sill. Fore and aft of the door opening it is soldered back into the standard loom wires. But maybe I am folowing the wrong route?
GuyW

that's the correct route certainly for all cars I've ever looked at / taken apart, from 1964 onwards. The rear loom joins to the front one at the top of the A post behind the end of the dash, with a bunch of single bullet connectors.
David Smith

Thanks David,
So, beneath the door opening, is the loom clipped to the face of the sill, behind the trim panel, or does it just lie along the floor?
GuyW

The loom is secured by self tappers to the inner cill by 2 metal clips (part number CHR0405) They look Like 1/2 a P Clip. The loom is secured about 1/2" from the floor.
Bob Beaumont

Thanks Bob
GuyW

Don't know if this will help
Mr Lucas's mystery colour chart that I stole off someone that stole it

willy

http://www.jcna.com/library/tech/tech0014.html

William Revit

Nick, when I installed a loom in another vehicle, I used a big 6 volt lantern battery to test connections and power circuits. Not enough oomph in a lantern battery so if you have a short circuit, your residual smoke will not escape.

Clive
Clive from Canada

Another suggestion I've seen is to use a battery charger for testing.
Dave O'Neill 2

I was just going to use the continuity test on my multimeter. It shows a value and, although I've no idea what it means, if the values were consistent I would guess that the cable is good. Experts, please pile in and tell me otherwise.
Nick and Cherry Scoop

Please. Before I start doing testing that might prove worthless.
Nick and Cherry Scoop

Probably explaining the obvious, but your continuity test on the multimeter will be measuring the resistance. Start by touching the probes together and you should get a row of Zeros or a very low number, depending on the level of sensitivity of the setting you are using. If you then touch the probes to the opposite ends of a single piece of wire you should get a similarly low reading.

This is useful for identifying that a) the wire that disapears into the loom at one point is in fact the same as the one re-appearing at the other end. And b) that the wire has no breaks in it, hidden deep inside the loom.

The other test I would do with the loom in place, but before connecting the battery, is to check for resistance between each wire and the bodywork. With the loom not yet connected and everything switched off this should give a very high reading, preferably showing infinity or an open circuit. If it shows a low resistance then there is a short somewhere on that wire and you need to investigate further before conecting up the battery.
GuyW

A couple of thoughts.
When you are testing for continuity on a red wire at one end of a loom, also test other wires next to the red one as there may be a short somewhere hidden in the loom.
Later midgets with NA/US spec had inline fuses going to the boot wiring. They were at the junction of the main loom and the section going back.
A new loom/harness is the way to go.
J Bubela

Thanks Guys. I really don't want to put in a new harness, so I think I will do some testing. Don't understand electricity even slightly, but I'm not bad at method.
Nick and Cherry Scoop

Nick

Get a new Autosparks one - easy to fit at this stage and good value. Old wiring can be corroded inside, let alone at bullet connections. Electrical faults, including earthing, can be a major issue for reliability.

I know more cost, time and delay! All I seem to do is suggesting more things to do.

Cheers
Mike

M Wood

Thanks Mike. Those Autosparks looms are awful expensive, and I'd want a couple of things added to it. I could spend 250 in lots of other places.

It's difficult to see why wires should be worse corroded in the middle of a loom run, when the ends I've cut back and stripped are in fine condition.

I hate wiring the dash. Or rather, I hate lying on my back with my head in the footwell and my legs in the boot.
Nick and Cherry Scoop

Nick, I think it's the insulation that deteriorates rather than the wire itself. You don't want a short circuit on an unfused feed. Also, the old connectors especialy the bullet ones will probably be trouble I would think. A deteriorated connection to a connector may cause volt drop, especially on a high current circuit e.g. the headlights meaning components don't receive the full 12v so e.g. light are dimmer, wiper motor runs slowly etc.

Yes, a new loom is expensive but not compared to the paint job!

Bill
Bill Bretherton

Nick
I would support Bill on this. My experience with my 60 year old loom was that the insulation was breaking down and there were all sorts of risks with shorting and potential fire.
As regards fitting it, I didn't crawl around in the footwell. I put the new loom in the car, I put the dash together with all the clocks and switches in place and then connected up the wiring and then fitted the dash to the car. I did it all from the cockpit sitting on an upturned bucket and occasionally the transmission tunnel (no seats fitted)
Bob Beaumont

Yesterday my Rover got new front discs and pads, so I shall postpone this decision until that bill drops onto the mat.

For the paint job I didn't take the dash out, Bob. I did release it, and tie it up temporarily, but all connections are still in place. I suppose I could drop it back enough to get in over the top if I disconnected speedo and rev-counter and was careful with capillary tube and oil pressure pipe. What else is vulnerable, discounting the (possibly) redundant wiring?
Nick and Cherry Scoop

Hi Nick

Oh I see you left the dash in! If you want to remove it yes disconnect the speedo an rev counter. The oil pipe just unbolts so is easy. I did carefully remove the water capillary tube by releasing all the connections along the pipe and removing the bulb from the radiator. I them removed the gauge complete. You may be able to just release the capillary connections to allow you to withdraw the gauge sufficiently to work on the wiring. You also need to disconnect the heater wire from the heater box, starter and choke cables. The dash will them drop about 10-12 inches clear of the car to get to the wiring. Its then a case of disconnecting the old and connecting the new!
Bob Beaumont

Thanks Bob. Going out there - may be some time.
Nick and Cherry Scoop

Whoops I should also have said you need to remove the steering wheel and the Bakelite bezel. The bezel is a bit challenging as its held by 3 small screws to the rear. They were originally Phillips headed no1 size. You do sadly have to crawl into the footwell to see the screw heads Sorry!
Bob Beaumont

Look what you made me do.

Not too difficult, because everything was disconnected at the working end. Oddly emough, I didn't remove the bezel. I will now, though.

Still haven't decided about the loom. With all my extras it will cost a lot:-

Radio
Clock
Ammeter
Interior Light
Fog Light
Driving Light

36 for the fog and driving lights alone, though you do get a relay in the circuit.

Nick and Cherry Scoop

BTW, my very first question has been answered.

Nick and Cherry Scoop

Ah, yes. Very pretty ;o)
Dave O'Neill 2

I thought so, Dave. I liked seeing them: they possess a sort of allure, but I'm now being given the feeling that it may be only skin-deep.

Can I just wire up the radio and clock locally? It occurs to me that any local unswitched circuit will do. What's nearby - perhaps a light switch or horn terminal?
Nick and Cherry Scoop

There's likely to be a suitable supply somewhere in the area, as a radio was a dealer fit option, I believe.

Edit: or maybe factory fit.
Dave O'Neill 2

Nick

You may not need too much modification. The radio and clock could come off the horn circuit as its not ignition driven. Don't need a modified loom. The ammeter goes into the non starter lead (brown) to the battery. Again no need for a modified loom.
Interior light could come off the light switch.
That just leaves the modified wiring for a relay...!

My frog has an ammeter and used to have a radio (couldn't hear it!). I have an extra wire in the loom from the rear of the ignition switch to the fuel pump so it cost an extra 35 as you say.

Bob
Bob Beaumont

Thanks very much, Bob. On the ammeter connection, two questions:-
(i) Are you positive earth?
(ii) Does it matter?
Nick and Cherry Scoop

Nick

Look at it this way, at least you can do the other job you were asking about - how to put in the rubber bulkhead grommet for the speedo cable - easy now when you disconnect the drive at the speedo end when the dashboard is unscrewed! Plus other bulkhead grommets.

Label the connections with masking tape and a marker pen before disconnecting anything.

Cheers
Mike
M Wood

Hi Nick

I am positive earth but it doesn't matter!! Basically you cut the brown lead and put the ammeter wiring in circuit to make a loop. If the ammeter shows a discharge when the car is running swap the connections at the back of the gauge. I have got a wiring diagram for an ammeter which I will see if I can post.

Bob Beaumont

Fitting an ammeter can be a bit more involved than it might first appear.

With a dynamo and the original wiring, it is a simple extension of the single brown lead connected from the control box to the starter solenoid, up to the ammeter, and a new cable back to the solenoid (using good grommets in the new holes in the bulkhead of course!). The control box acts as a junction box for all the original circuits, with a single connection to the solenoid.

With an alternator, both the feed from the alternator AND the original brown lead have to be extended up to the ammeter, with the same new cable back to the solenoid. The brown lead has a number of other connections made to it within the harness, so again a single connection to the solenoid.

If you add in any new circuits they also must be connected directly to the ammeter (obviously via fuses first) - driving lights, reversing light etc.

Lucas ACR alternators are very helpful in one way, they have 2 x 35A Lucar output terminals, so the larger output versions can be fitted with 2 smaller cables, instead of one large one. This is particularly relevant for higher output alternators - 55A are very common now, even 75A are easily available as a straight swap.

The attached picture shows the back of the 60A-0-60A ammeter that has been fitted to our Minor for the last 45+ years, and gives an idea of the sizes of the cables involved. I stripped and extended the original wiring harness, which was then re-covered by Autosparks in the original fleck colours. The large single brown wire is the feed to the battery (1 x 60A, 120/0.30mm or 8.50 sq mm), and on the other terminal are the twin brown connections from the alternator (2 x 35A, 65/0.30mm or 4.50 sq mm).

The other cables feed the original ignition and non-ignition circuits, and also 2 additional fuse boxes, one for non-ignition circuits and the other for ignition fed circuits, via a 40A relay.

Richard


Richard Wale

I will have to digest this later.
Richard - you have frightened me quite comprehensively from your fourth paragraph onward - it was going so well until then - but I shall look at my existing ammeter wiring and see if I can make sense of it. This is unlikely, but at least I can ring out the wires and make a diagram.

I am positive earth and dynamo.

What I really came in to say is that when I took the steering column bezel off just now, I found rawlplugs in the three plastic fixing tubes! Is this as it should be? Will the concours judges angle their little mirrors to check?
Nick and Cherry Scoop

Ah ha!

A common little bodge!! It should have threaded inserts which should hold fairly tightly in the plastic. They look like tiny helicoils BUT they often come loose and fall out and can't be found.. I got internally threaded brass bushes made to go in mine. They are a tight push fit and I added a bit of epoxy glue to help them stay put.

The rawlplug idea isn't bad and I promise I won't tell the concours judges. I managed to save 2 of the inserts with the original screws somewhere. The thread on the inserts I could not identify It wasn't BA or UNF

As you are using a dynamo the first two paras of Richard's helpful note are the main concerns.
Bob Beaumont

Thanks, Bob. I was wondering what the correct fixing might be. I believe I shall use rawlplugs, if I can get some NOS.

I've been looking at my ammeter. It has only one wire to each terminal, and they come from the junction I've shown below. The third wire rejoins the loom behind the dash, heading back out through the bulkhead towards the fuse box and voltage regulator.

Nick and Cherry Scoop

Nick,

Looking at the wiring, sorry, I do think you should replace the harness. With corrosion in the bullet connectors, you will get heat, and with heat you could get much worse!

Secondly, the size of the cables concerns me - what size are they? How many strands? The largest cable that will go into a bullet is 28/0.30 (28/0.012 in old money), and that is too small for the main output cable, even for dynamo. The lowest dynamo output is 19A, and a 28/0.30 cable is rated at a maximum of 17.5A.

For any dynamo output cable I would want to see a 44/0.30 cable used - probably was not done when new, but with low wattage head light bulbs at that time, the dynamo was probably not expected to work very hard. Since you planning to fit additional lights (and maybe halogen headlights?), plus other electrical extras, please uprate the dynamo output cable - too small not only causes heat, but will not allow the full output of the dynamo to reach the battery - it gets lost trying to get down the cable!

The attached tables shows the current carrying capacity of the standard range of automotive harness cables.

Richard



Richard Wale

Yes that is where my ammeter is connected. If you do get a new loom you will need to keep the lead insert and attached length of wire that goes into the battery clamp. The replacement loom has a normal brass screw connector which is no good if you want to retain the existing battery terminal clamp.

On mine I cut off the connector and reused the lead insert with about 6 inches of wiring. I connected a wire from the ammeter to the wire with the lead insert and connected the second wire from the ammeter to the new loom where I had cut off the brass screw connector. ie the ammeter was in series with the brown input wire. Its how it is described in my instruction leaflet I had with the ammeter (Smiths 1970)


Bob Beaumont

Thank you, Richard. If I order a standard harness from Autosparks, I assume it will come with a main output cable that fits like a washer to the bolt of a modern battery terminal clamp. Would you then run the loop to the ammeter yourself, or should an ignorant cove like me ask Autosparks to include it?
Nick and Cherry Scoop

Sorry Bob - I managed to miss your jolly helpful post: I started my reply to Richard, was called to eat soup, then came back and finished and sent it (the reply, not the soup).
Nick and Cherry Scoop

Nick,

Oops, I was still in 'alternator' mode when talking about the 'main output' cable to the ammeter; with a dynamo the other cable that needs to be the 'right' size is the yellow one from the dynamo to the control box. That also needs to be able to take the full output from the dynamo.

Although in normal running, the brown wire from the control box 'A' terminal to the battery doesn't see the full load, because the lights and everything else are supplied by the dynamo charge via the control box 'A' and 'A1' terminals, it still needs to be sized for whatever 'full' load can be switched on, as that is what the battery will supply through the brown cable if the engine is not running, or at idle, when the dynamo does not charge very much/at all.

The brown wire from the 'A' terminal on the control box can be connected either as original, directly to the battery, or to the battery side of the starter solenoid/pull switch. With an ammeter, the brown cable goes from the 'A' terminal to the ammeter, and the return from the ammeter to the battery/solenoid.

Unless you have the right size cable, soldering iron and terminals, I would get Autosparks to include the ammeter circuit; it also saves making a joint in the cable - what connections do you have on the ammeter?

Do you have any thoughts about an alternator in the future (or for original looks, a 'Dynalite' type alternator, within a dynamo body?).

If so, it would be worth discussing with Autosparks about fitting an uprated ammeter circuit now. You will need more than double the existing cable capacity for an alternator.

Richard
Richard Wale

Nick,
When you are next getting personal with your Sprite, could you please measure the diameter of the hole in the bulkhead that the main harness goes through. Or if easier, the outside diameter of the larger rubber grommet that fits this hole. I bought a grommet supposedly for this location but it is too small. The grommet itself measures 1 3/4" externally, as does the hole in my bulkhead. But that doesn't allow for the edges of the grommet to extend either side of the hole so it just drops out. As I replaced the bulkhead on this car, I am not sure if the hole is too big, or the grommet too small!

Incidentally, now you have released your dashboard, and before you re-attach it remember to attend to the wiper rack, washer jets and demister funnels. They are all a lot easier to fit before the dash goes in!
GuyW

I'll measure tomorrow, Guy. And thanks for the reminder. At the moment the scuttle-mounted stuff has to wait, because my painter has some rubbing down and re-polishing to do there when he brings the doors and bonnet over.
Nick and Cherry Scoop

Richard, I took your posts and a wiring diagram downstairs last evening and tried to let it sink in gently while being gripped by Friday night on TV. Later I shall consult my notes and decide what to order. Laura is in a 'of course you must have it' sort of mood just now, so I must get on with this.
Nick and Cherry Scoop

Rchard, I fully agree with your suggestion but the frogeye (and possibly the Mk11) has an unusual take off for the non starter wiring. (See Nick's phot0) if you want to retain the original battery clamp you need to retain the lead connector. Autosparks do not supply this.
Bob Beaumont

Guy - my grommet measures about 2 1/8" externally, 1 3/4" in the groove, and the bulkhead hole is just 1/32" shy of 1 3/4".
Nick and Cherry Scoop

Thank you, Bob! You have reminded me of originality - one of the things that I'm aiming for, and on this topic was in danger of losing (among the technicalities that always seem to baffle me).
Nick and Cherry Scoop

Thanks Nick. So my bulkhead hole is corrct and it is the grommet that is undersized. Rather as I thought.

I wonder,- if a grommet is described as 1 3/4", should that be the size of hole that it is designed to fit, or the OD of the grommet?
GuyW

Bob - did you use bullets for the 4-way junction above the battery clamp? (I've made a note of capacity required, from Richard's cable table)

BTW, for surfers who like trivia, the picture of a MkI harness in Autosparks' site includes a corroded old cable. Shurely shome mishtake.

But the harness set does include the grommet!
Nick and Cherry Scoop

Another question for Richard:- I've got three bags of bullets in my ar*enal. The scrawl on them seems to read:-
309x50
314x50
328x50
These codes are similar to those in your table, but not quite.
Nick and Cherry Scoop

Nick,

I didn't use bullets but soldered the wires from the ammeter to the lead connector and the return to the control box. I then covered them in heat shrink. I was a bit worried the bullet may pull out and everything going dead (except the starter!) Looking at you lead connector in the photo it has been cut quite short. The wires may have corrosion and may be difficult to solder. if so you may prefer to retain the bullets assuming they are nice and secure.
Bob Beaumont

Nick,
Richard's table ties up, see PVC & Braided Cable -
https://www.autosparks.co.uk/faq

"Cable Application guide
PVC & Braided Cable

5.75 Amp - 9/0.3 - 0.65mm2 - LT Ignition, Side & Tail Lamp

8.75 Amp - 14/0.3 - 1.0mm2 - General Wiring

17 Amps - 28/0.3 - 2.0mm2 - headlamps, Major Accessory Feed

25 Amps - 44/0.3 - 3.0mm2 - Dynamo, Control Box, Ammeter

9 or 14 strand cable?

We have been criticised in the past for using 9 strand cable when it was never used originally. This was because in the old days Lucas manufactured two sizes of 14 strand cable. 14/0.10 (14/0.25mm) and 14/0.12 cable. (14/0.30mm). As all of the larger sizes of cables had a strand size of 0.12 (0.30mm), Lucas rationalised their manufacturing and replaced the odd 14/0.10 cable with 9/0.12 (9/0.30mm) giving an equal carrying capacity."


Probably your bullets -
https://www.autosparks.co.uk/electrical-components/bullets-connector-sleeves.html

bullets to suit 9/0.30 (non-braided) cable (C309)

bullets to suit 14/0.30 (non-braided) cable (C314)

bullets to suit 28/0.30 (non-braided) cable (C328)

[bullets to suit 44/0.30 (plastic or braided cable) (C344)]
Nigel Atkins

Guy - grommets - described by the hole they fill, and the centre hole too, e.g.
https://tinyurl.com/yasurc4k
David Smith

Thanks David
This is the one I bought,
http://tinyurl.com/yakwbmy3

listed specifically for that bulkhead application, but identified as 1 3/4" OD rather than the 1 3/4" Hole Size. A subtle, but significant diffference as it just falls out!

The Autosparks one is also half the price!
GuyW

If I don't say it then Nigel might:- serves you right for shopping at ....
;-)
David Smith

Nick,

Ref - bullets. Nigel has explained all!

Richard
Richard Wale

I've never said Moss are all bad, I don't say any company or person is all bad, that's why I continue to sometimes buy from Moss, I just lower my expectations of company ethos.
Nigel Atkins

This thread was discussed between 03/04/2018 and 08/04/2018

MG Midget and Sprite Technical index

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