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MG Midget and Sprite Technical - Stop Lights

Perhaps one day the electric god will endow me with a little understanding, but for now I'm wandering around in dark ignorance, as has been the case since my birth (early in the last century), bumping into painfully hard things and cursing feebly.

How do stop lights work?!!? Manuel shows a single line running to the clever, do-two-things-at-once lamp, with a single switch between fuse and lamp.

If you're kind enough to reply, please pitch it at mental age 4.
Nick

Not difficult to explain I am sure.

Current flows from the fuse to the brake lamp switch! basically it waits there until the switch is pushed (close the switch) when the switch closes the current flows to the lamp. The lamp has 2 filaments, Brake/side light, so this current from the switch is fed into one of the filaments (one of the 2 contacts on the bottom of the lamp [bulb to the non electrical types]) the filament in the lamp is then connected to earth (via the metal at the base of the lamp/bulb) and so the current now flowing from fuse through switch through filament in lamp to earth causes the filament to get hot and glow incadescently and emit light!

How easy is that?
Robert (Bob) Midget Turbo

I tried to write a bit of an article on understanding electrical systems on our website. Try this link and select "how to use a multimeter" it may help in future, I would like to think!

http://www.mgcars.org.uk/mgcc/midgetreg/workshop.shtml
Robert (Bob) Midget Turbo

you dont have a bad switch do you...appeartly vary common problem, for the midget/AH

Prop
Prop

I think Nick was querying how there can be a single live feed yet 2 brake lights.....
David (davidDOTsmithAT stonesDOTcom)

Not exactly, David, but close. What I don't understand is, how does the sidelight get switched on, without the brake light?
Nick

By the second wire that goes to the lamp fitting. The rear lamp has 2 filaments that are connected to the 2 connections on the bottom of the lamp/bulb and have a common eart through the metal base.
Robert (Bob) Midget Turbo

the side lights are tuned on thur the insturment light IIRC... But cant say for certian as ive redone my side light to flash with the turn signals
Prop

This is for a Frog. And I can't see a second wire. 16 and 17 are the stop/tail lights, and 18 is the stop light switch.



Nick

More . . .


Nick

Nick 16 and 17 are at opposite sides of the car and are representitive of the 2 filiments for brake lamps one in each sidelight fitting. The second element in each lamp is represented by the 16 and 17 that are connected to the light switch (6+38)
Robert (Bob) Midget Turbo

15 of that particular "ensemble" is the number plate lamp.
Robert (Bob) Midget Turbo

see lower centre for the 'other' 16 & 17. Not the most brilliantly drawn wiring diagram...
David (davidDOTsmithAT stonesDOTcom)

just one thing to add

I think stop lights is not the correct name
Brake lights is mutch more suited

because pushing the brake pedal does not mean you wil stop..... ;)

And in dutch stop lights means trafic light
Onno Könemann

Nick
I think the simple answer is that there are two "16's" and 2 "17's" which is obviously very confusing.
Graham M V

Got called away, so just back.

TWO diagrams of the same lights, on different sides of the picture?!!? Ridiculous! (I will never be an engineer)

Still, I think even I can test the switch, and it can't be the fuse if the flashers work, can it?

Thank you.
Nick

It's the switch.
Thought you'd like to know.
Water in the fluid, I suppose?
Nick

Nick - Nothing to do with water in the brake fluid, the switch just died from old age (it it was an original. Problem is that when you replace the switch, the replacement is junk. You have two options at that point. 1) order the switch (SW 32)from Ron Francis Wiring at: http://www.ronfrancis.com/ (expensive, especially from your side of the pond) or 2) go with the standard replacement switch and make and install a relay/arc suppression circuit at the same time to protect the switch. For instructions on making the circuit see the article, Brake Light Relay in the Other Tech Articles section of my web site at: http://homepages.donobi.net/sufuelpumps/ Cheers - Dave
David DuBois

This thread was discussed between 17/08/2009 and 20/08/2009

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