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MG Midget and Sprite Technical - RWA Midget lighting circuit

Hi,

My car is stripped and I am making my own wiring loom but I am trying to retain the column stalk functions for use with relays for the lights

Just trying to understand the wiring of the standard cars column stalk and light switch.

I think the root of my confusion is the column stalk behaviour, I just need to confirm if this is correct?

It appears to have 3 positions as regards lighting functions: (Assume dash light Sw. is on)

1.) 'At rest' centre position = “Dipped Beam only” (constant)

2.) Pull towards me = “Main beam + Dipped beam” (momentary action)

3.) Pushed away from me = “Main beam only” (constant)


In 1. “Dipped beam only” (Blue, +12v from dash light Sw.) connects to (Blue / Red - Dipped beam)

In 2. “Main beam + Dipped beam” connects (Blue, +12v from dash light Sw.) to (Blue / Red - Dipped beam) as above but also connects (Purple, fused +12v supply) to (Blue / White - Main beam)

In 3. “Main beam only” connects (Blue, Live feed from light switch) to (Blue / White - Main beam)

Sorry I don't think I could have written it in a more confusing way!

Using relays I was planning to have “Main beam + Dipped beam” active with the column stalk pulled towards me or pushed away, with Dipped beam in the ‘at rest’ position. Is there a specific reason legal or otherwise for the “Main beam only” setting?

Cheers

Spencer

S Deakin

Not a legal problem but something to think about.

Very small current throught the column switch as you are using relays, so OK.

When you have main beam on constantly ahead postion not when flashing, there is double the current going through the earth spade on the bulb, on the headlamp connector and on the earth wire from the connector.

You can use a thicker earth wire but the electrical connection on the headlamp connector and the bulb earth spade will be over loaded.

The bulbs are cheap to replace but you will have to look at the connector block.

Probably just about OK with 60/55 watt bulbs but not with 100/90 watt bulbs.

eddie
Eddie Cairns

Hi Eddie,

Thanks for taking the time to reply,

I have seen 100/80w bulbs (Moss) for sale not sure what 80 watts as a dipped beam looks like? and if it's acceptable for road use? (I don't mean legal just sensible / acceptable).

If we have both the Dipped and Main switched on:

(Worst case scenario) 100 + 80 = 180W / 12V = 15 Amps

or assuming healthy voltage:

100 + 80 = 180w / 13.5w = 13.3 Amps

Which the ground wires I am using will cope with easily.

I have no idea what the current rating of the spade terminals of the holder are - do you have a spec sheet for it as you say it will be overloaded?

TBH I am far more likely to use 60/55 which would only be 115W / 13.5V = 8.5A, which sounds pretty tame.

But without knowing the ratings of the bulb holder I don't know.

Do you know if my description of how the column stalk works w.r.t. lights is correct or not?

Cheers
S Deakin

Spencer, your understanding of the switch is correct.

I would worry about the amount of heat being produced by two filaments being lit at the same time.
Dave O'Neill 2

You just need three relays.

Relay 1 takes a signal feed from the dip wire and lights the dip element.

Relay 2 takes a signalfeed from the main beam wire and lights the main element.

Relay 3 takes a signalfeed from the main beam wire and lights the dip element.

To be honest using the relays and say a good quality bulb the headlights will be much better than the originals.

Put on Cibie H180 light units and there is no good reason to light both filiments at once.

Eddie
Eddie Cairns

There was a standard size 7" headlamp called the Cibie Biode.

Rather than one H4 double filament bulb it had two H1 single filament bulbs to get round the heat problem in one bulb.

There are a pair on ebay.

http://cgi.ebay.co.uk/Cibie-Biodes-Works-Escort-mk1-mexico-twin-cam-mini-911_W0QQitemZ270545309164QQcmdZViewItemQQptZUK_CarsParts_Vehicles_CarParts_SM?hash=item3efdc1cdec
Eddie Cairns

Cheap too!
Brad (Sprite IV 1380)

Dave,

Thanks, at least I understand what the standard car 'did' :)

Eddie,

Thanks again for taking the time.

TBH I have no burning desire or need for prolonged Main + Dipped running it was just that today I was looking at integrating the column stalk into the loom I have made, when I figured out what it did I needed to understand why it did it?

Then I had a crisis of confidence that maybe I was missing something in what I planned to do as far as Main beam switching.

I will look into the Cibie H180 as I was planning on fitting 'better' headlights as part of my rebuild and had made no decisions. I assume they have a 'better' reflectors as they use a H4 bulb. Any ideas on a good resource to look at as far as the relative performance of H4 based midget sized lights or non H4 for that matter.

I suspect the Biode is a trifle specialised and pricey for my needs.

Cheers
S Deakin

The Cibie H180 units are excellent quality and great performance.

Just get a pair, some of the better 60 /55 watt h4 bulbs but you must use relays.

That will do the job!

Which Best Buy for headlamp bulbs

Bosch Pure Light, £21.98 a pair


eddie
Eddie Cairns

Eddie, Cheers

The three lighting relays are already installed!

But I think it will be a little while before I am at the stage of fitting the headlamps in the rebuild.

Cheers



S Deakin

wow, that's weird.

I replied to (I think) a slightly different version of this thread earlier. Now my reply is "all by itself", and here this thread is (both threads with the same title)!

Norm "funny thread" Kerr


Norm Kerr

Yeah Norm, I was right confused by your reply to imaginary things, was getting worried about you! And I looked for another thread it could apply to and didn't find this one then, but later I did, so then I am worried about me...

FRM
Fletcher R Millmore

Norm,

That must have been the Parallel Universe thread?

In have just found your response to the thread you created of the same title? Indeed very confusing, I did have some problems posting earlier, maybe I was perched on some gateway bewteen the two?

Anyway in that particular 'parallel universe' my car is completely finished just in need of the column stalk wiring, sadly in this one I have 'one or two' jobs to do just yet.

P.S. thanks for the links to the PDF's

Cheers

Spencer
S Deakin

whew, glad I could help.

Norm "I must be going crazy. No I'm not. Shut up, both of you!" Kerr


Norm Kerr

It might be because Eddie made Spencer use three relays, when two would do, or because Spencer wants to put Main & Dip on at the same time, which there's no good reason to do. If your car will go 150 mph, OK, but decent 60/55W lights and good wiring are certainly adequate to over 100.
The actual bulb spades are not a problem for two filaments; they're good for about 15A. The harness plugs are not, and they are not much good for even standard use after a few years, There are some excellent HD Hella connectors, and lately I've gotten ceramic ones from Daniel Stern. The biggest problem is the pigtails from the lamps to harness, including the ground leg; these are not adequate for even standard 60/55 lights, causing significant voltage drop, around .33V or 8-10% of light output. Redo all this with good connectors and 14ga US or 28 strand old Lucas wire.

FRM
Fletcher R Millmore

FRM

Agree, two relays, 60/55w bulbs, no need for dip and main on at the same time, good connectors, correct wire, well designed light units, sorted.

eddie
Eddie Cairns

Hi Fletcher,

Three relays:

1st relay, Dipped beam power feed
2nd relay, Main beam power feed
3rd relay, Sidelights + brake lights + Dash lights + Interior light feeds

The fact that side lights power feed share a relay with other lighting ancilliaries is just how I chose to do it keeping the relay count down.

As stated earlier:

"TBH I have no burning desire or need for prolonged Main + Dipped running"

So it's not that it was a specific requirement, the std Midget does put both on in the "stalk pulled back" position, I meerly replicate this behaviour for the rare instances I will use them. Switching the dipped beam off when the Main beam is activated was a complication I decided not to bother addressing rather than specifically wanting both on.

Not sure if 'it' will do 150 mph, (180 bhp / 700 kg - estimates) but pretty sure I will bow out before the car if it does in daylight!

The wiring to and from each light is rated at 22 Amps for both +12v and GND. It's Raychem Type 55M (Mil / Aero Spec) 20 swg x2. With Deutsche / Autosport Motorsport connectors.

The chassis part of the loom:






S Deakin

Mocking up in car:

Edit:

Brake lights is a typo - not included in sidelight relay!


S Deakin

Sorry!!!!!!! I tried to add this to the previous post but it was too late!

FRM / Eddie,

Can you post your schematic that uses 2 relays and can turn the dipped beam off when Main is on - sorry just being thick but my scribblings are not yet fruitful in trying to deliver this as I want to keep the 'fusing' for the two circuits seperate as I dont want to lose all lighting if the 'fuse' fails...

Cheers

Spencer
S Deakin

Spencer -
The OE system uses one each main beam and dip beam leads to the front, from the dipswitch. These normally split at the bonnet latch platform to go to each lamp. I fit the two relays at the split, and use the OE wires to actuate the relays. That gives main or dip, never both. Except, on the OE setup, the dipswitch in the center "dip" position feeds the dip lead, and when pulled back also actuates the Main lead, so both are on briefly when you flash the lights.

Fitting the relays at the front split makes it a non invasive retrofit without cutting up the harness. I run two fused power leads straight off the solenoid terminal point to the relays. This gives the least feet of power lead wires, control leads don't lose voltage.

I'm not sure what 20swg actually is; gauge systems are arcane and confusing. The 14 AWG is the American designation, and old Lucas is 28 strands of .30 mm each, rated at 17.5A, metric equivalent is a bit over 1.0mmsq (16.5A). This is the size of the OE main leads to the split point, more than adequate if the wires are as short as possible; with the relays so situated, the load wires are about 5 feet (7 including the earth leg) from solenoid to lamp, and give an unmeasurably small V drop under load.

Send me an email and ask for "electrobabble"

FRM
Fletcher R Millmore

Spence

You do not need the relay to switch the dip off.

DIP BEAM
The wire from the dip switch that originally would power the dip beam goes to terminal 86 on the relay.
Terminal 85 is earthed.

Terminal 30 on the relay is from the battery via a fuse. Terminal 87 on the relay to the dip beam terminal on the bulb.

MAIN BEAM
The wire from the dip switch that originally would power the main beam goes to terminal 86 on the relay.
Terminal 85 is earthed.

Terminal 30 on the relay is from the battery via a fuse. Terminal 87 on the relay to the main beam terminal on the bulb.

See this page for a diagram.

http://freespace.virgin.net/tommy.sandham/relays.htm
Eddie Cairns

Spence

You do not need the relay to switch the dip off.

DIP BEAM
The wire from the dip switch that originally would power the dip beam goes to terminal 86 on the relay.
Terminal 85 is earthed.

Terminal 30 on the relay is from the battery via a fuse. Terminal 87 on the relay to the dip beam terminal on the bulb.

MAIN BEAM
The wire from the dip switch that originally would power the main beam goes to terminal 86 on the relay.
Terminal 85 is earthed.

Terminal 30 on the relay is from the battery via a fuse. Terminal 87 on the relay to the main beam terminal on the bulb.

See this page for a diagram.

http://freespace.virgin.net/tommy.sandham/relays.htm
Eddie Cairns

FRM,

This is the wire I use:

http://www.tycoelectronics.com/commerce/DocumentDelivery/DDEController?Action=showdoc&DocId=Customer+Drawing%7F55M0411%7F21%7Fpdf%7FEnglish%7FENG_CD_55M0411_21.pdf

Basically very 'thin' wire for the current it carries:

I am not retaining any of the 35+ year old loom, every part is remade.

Hi Eddie,

Your diagram shows a single switch being used to switch from main to dipped, but the reality is that two switches are used, the dash switch is used to turn the dipped beams on as per all 'normal' road cars. This dipped switch stays ON throughout whatever we do with the lights. Then we use a column stalk (a seperate switch) to acivate main beam - how do we use two switches as the Midget does to turn the main beam on and turn the dipped off with just two relays?

Cheers

Spencer



S Deakin

Try this for the wire and then select the PDF: (UK SCD)

http://www.tycoelectronics.com/catalog/bin/TE.Connect?C=16377&M=PPROP&P=87033&BML=&LG=1&PG=1&IDS=133307,133461,134232,134238,134239,134240,134241,134242,134244,134245,134246,134250,134252,134253,134254,134353,134354,134355,134356,134357&N=3

Cheers
S Deakin

Spencer -
The wiring goes like so:
Batt>solenoid terminal> N to dash switch >U to dip switch > UR to dip or UW to main. At the dipswitch there is also a fused always hot P (N>fuse>P), which is momentarily connected to UW to flash main beams.

AKA, the dash switch turns on first the sidelamps, and then adds the headlamps, and the dipswitch selects which headlamp beam is used.

FRM
Fletcher R Millmore

But with just two relays?

As you and Eddie are suggesting?

Cheers
S Deakin

The light switch sends power to the dip switch.

In the ahead position the dip switch voltage goes to the main beam relay switch coil. Nothing to dip relay switch coil.

In the normal position the dip switch voltage goes to the dip beam relay switch coil, noting to the main beam relay switch coil.

So you can use this fact to decided which relay is switched on. The other will be off.

In the flash position when you pull back the dip switch both relays will be switched on but only while the dip switch is pulled back. Leave the switch and the dip only is switched on.

So in normal or ahead positions there is no case where a voltage is going to both coils.

I do not have any sketching software handy to do a drawing but will post tommorrow if needed.

eddie
Eddie Cairns

As far as headlamps are concerned, yes.
Your proposed third relay for side/tail is controlled off the R wire from the dash switch. That would have the dash switch only carrying control current, as would the dipswtch. All load current is going through the relay fused feeds.

FRM
Fletcher R Millmore

Eddie / FRM,

Thank you for your patience, if you say it (by 'it' I mean using only 2 relays and maintain original car functionality) can be done I am sure it can, I am just "not there yet" in understanding how...

Eddie, Yes what you have described is the functionality that we want but doesn't say how we do it with 2 relays.

If we ignore the fact that I am using a 3rd relay for the sidelight / ancilliary lights and just consider the dip / main functionality.

Bearing in mind that my current setup uses 2 relays, ang gives:

Dash and column switches only 'see' control voltages and not the full current of the lights.

Both the dip and main circuits are seperately supplied and 'fused', the fuse being between the +12v Master Sw. supply and each relay / switch, therefore in the event of one fuse failing the other circuit still works. IMO this is the best place for the fuse as it then protects the switch, relay and more of the wiring, the diagram earlier showed the fuse being near the lights which means everything (switches / relays) are still exposed to +12v even if the fuse blows.

My system mimics the std car in all areas except in the 'pushing the stalk away' from me which in my system powers both main and dipped lights - not because I need or want it to, just thinking it would require another relay to provide this behaviour so I didn't bother.

So I just need to see a diagram to show how?

Cheers and thanks again for taking the time

Spencer



S Deakin

Spencer -
I don't know what sort of dipswitch you have, but the normal one works as I said in "the wiring goes so:". The circuit is exactly as shown in the book, except that you hook the UW and UR wires to the relay control instead of the lights. I don't have a way to send you a diagram, but you shouldn't need one. If you can post a diagram maybe I can figure out why you are confused.
The diagram Eddie linked for you is correct (end of page).
FRM
Fletcher R Millmore

FRM,

I am pleased to announce to you and anyone pained by reading this thread that the 'penny has dropped'...

I designed and made my new car loom with no reference to what the standard car loom did as I haven't retained any of the original switchgear or any other part of the cars electrics... (save for rear lights and possibly fuel sender / gauge)

The exception to the above has been to retain the column stalk for main beam and indicator functions...

So at which point I start to 'bell out' (continuity test) the column stalk to see what it does so I can integrate it into my loom...

In order to understand the column stalk behaviour I end up having to understand how the std car lights work (and the original reason for this thread)...

So the system I designed has a dash switch to turn the side lights and the dipped beam on...

My column stalk is going to be the switch to turn the main beam on and off and is entirely seperate from the dip switch...

So I have been trying to understand how my loom can be made to work with just 2 relays... The answer is it probably cannot as I want the two switches to be entirely seperate for reliability reasons, both you and Eddie are of course specifically talking about the Midget loom having 2 relays added to it, a system which has the dipped beam passing through the main beam switch device (Column stalk)

Cheers
S Deakin

I have a pair of the Cibie Biodes that I would be happy to sell, they are in good condition, saved from a rally Escort may moons ago. The advantage was that you could run 130w bulbs before the advent of high wattage H4 type bulbs.
They are a v good light but they are quite bulbous tend to make a spridget look a bit like Jane Russel if you get my drift !
Standard fitment on many 60 and 70's Ferraris etc.
Ian
Ian Webb '73 GAN5

If all the lights go out at once it can be very confusing (Google "G-BYAG") so i rewired the red lightweight car so that putting the main light switch on sent power throught the main relay to the low beam. This was the default position. When the separate switch (not using a column switch assembly) was moved from LOW to HIGH beam it would send 12volts to the relay energiser which was then moved electrical flow from one terminal to the other. Since the relay was sprung to the low position, any failure of the 'dipswitch' would make the relay default to LOW. A seperate flash button would send 12 volts to the wire downstream of the relay to the HIGH bulb.

All laws met and the system only needed one big main switch and one relay. If the relay died then you still have a flash facility.

In the pic the dipswitch is by the left hand side, next to the mainbeam warning light and the starter button (ex supermarine spitfire) and can be moved without taking your hand off the wheel.

Does this all make sense?


rob thomas

Spencer,

I have followed your thread over on turbosport.

I was wondering if by any chance you would be willing to share your wiring diagram. I am about to embark on yet another epic adventure involving wiring and to date i only use a diagram thats floating round the grey matter in my head.

Thanks in advance.

Pete

(p.s i hope you are still within budget and please update us with your back axle if you have anything further done)
PJ Moore

Pete,

Sorry I understand you comment on the 'lowered spring pans' post now!

Unfortunately work and other activities are hampering progress at the moment - but not all bad as I spent the day testing at Snetterton yesterday (even if it did rain on and off - what's new?)

As regards the wiring schematic I always start with a mass of spreadsheets listing what connects to what in each connector and at the last count I was up to about 25 spreadsheets. I do the schematics last as the spreadsheets are perfect to make a loom from but hideous to use for fault finding once installed in the car. (At least I know it's the white wire!)

Once I have debugged it a little further as I am still at the stage where I am modifying (polite word for addressing c*ck ups) you can gladly have a copy as it contains nothing trick or clever.

It has however ended up quite specific to the ECU / Dash I am using (Pectel SQ6 - Omega D3 dash)and the ETA Master Switch, which means it could be of limited use. At the last count the only original Midget electrical items stiil left in the car:

Wiper motor (2 speed) Oops I must contact John Collins!
Rear lights
Fuel gauge / sender (Which could still change if I can get the D3 dash to do what I want)

Cheers

Spencer
S Deakin

Well it sounds awesome

Wiring is my major downfall which is why i asked. No matter how many times i am shown things wiring wise, unless its adding something small in afterwards im pretty stumped and i despise diagnosing faults.

I am however quite nifty at honda wire tucks now, but then thats nothing harder than colour matching.

i am thinking now to copy your method with the spread sheet idea and work from that. mainly due to the fact i want to have a very very gucci wiring loom that is hidden out of sight.

I have a selection of milspec bulkhead connectors to use up so may aswell go the whole hog

Thanks in advance

Pete
PJ Moore

This thread was discussed between 20/03/2010 and 25/03/2010

MG Midget and Sprite Technical index

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