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MG MGF Technical - Brake Lights

Hi, I have a problem, my brake lights seem to be on all the time, apparently there is no adjustment on the brake light switch, but if you lift the brake pedal up slightly the lights go out, please anyone help ....before the cops bang me up !!!!
Phil Jones


It is likely that the brake light switch piston has been pushed inside the cylinder. Remove the switch from behind the Brake pedal, it just twists to one side and pulls out. Remove the electric connection and then carefully extract yourself from the precarious position you have got yourself into, upside down under the steering column.

Once the switch is removed give the piston a hard pull outwards and it should come out from the cylinder, then just replace and all should be ok.

If you have no play in the cylinder then the switch could be worn and you will need to purchase a new one.

Hope this is all it turns out to be.


... careful disagree.
Chris is right with the adjustment, but IMO not with the theory, cause the light stays off when the switch is released.

>...has been pushed inside the cylinder.

Not the switch changed the length.
The brake pedals and attached mechanic settles. This means the pedal arm got deaper and increased distance to the switch.

Happens almost only once in the MGF live when the pedal got kicked hard.
There is a changed design switch availiable since MY2000 but almost the new pre-setting by pulling out the switch joint cures the problem.
Pull until it does a ratchet noise and a small notch gets visible.

Dieter Koennecke

Sorry Dieter but he's right, the break light switch switches the lights OFF when pushed, thus if it is adjusted so it is shorter it cannot be depressed properly by the break pedal, the over shortening comes from lifting the break pedal with your foot(not just the spring).
The switch comes out by twisting and pulling directly down. Then tug the plunger _hard_ and it will extend by a good inch. Reinsert by pushing the break pedal and reinserting the switch, when you let go of the break pedal it will readjust to the correct hight, but if you pull at the pedal then it will over adjust and you will be back where you started.
The cure may be temporary (i've had to do it twice), and someone here as added a small self tapper to the top of the switch to permenentaly lengthen it, this might become an option if you have further trouble
Will Munns

Thanks Chris , Dieter , Will

Thanks for your information, I am pleased to report that the problem has now been solved as you stated, take switch off pull the plunger outwards and re-install the switch, it works perfect now , and Mr Policeman can't feel my collar now :-)

Cheers all and Thanks


Phil Jones


Plunger switch mounted inverted above the short leg of inverted L shaped brake pedal. Pedal pivots about the 'joint' between the long and short legs, rubber foot plate is attached to the end of the long leg.

This means that when you press the pedal forwards, the short leg (perpendicular to the long leg) travels upwards depressing the switch and turning the lights ON.

Pushing the plunger turns lights on.
Releasing the plunger turns lights off.


Leg is inverted L shaped, pivioted around the corner, but the "natural" position of the pedal is resting on the switch, holding it pushed (lights off), pressing the pedal releases the switch- it is this way around so varing travel on the pedal all leaves the switch fully released. If you think about it why else does the switch shortening cause the light to stay on?

Will Munns

Because a shortened switch will trip the sensor.

Will, try removing the switch and pressing it by hand. The operation is obvious.

Upward movement of the pedal PRESSES the switch, therefore it MUST turn the lights ON when depressed. The internal ratchet/self adjusting mechanism merely adjusts whereabouts in the plungers range of mevement the switch activates.


The switch is inverted above the short leg. pushing the pedal forwards moves the horizontal leg upwards, because the switch is ABOVE this leg, the plugner is DEPRESSED by the brake pedal. If depressing the switch turned the lights off, they would be on all the time and only go off when the pedal is depressed.

SF <--- shutting up now.

Strange on my car the switch is below the pedal (in that you pull it down after twisting it to release) and with the switch out (no presure) the lights are on - I was sure about this, but you put doubt in my mind last week so I checked (and then coludn't be bothered to put the switch back because it was late, then forgot for three days - oops! still no tailgaters).

Will Munns

Interesting, Scarlet's is above the pedal (or it was when i replaced the throttle cable recently, i made a point of removing it, and generally having a good look at how it fitted and its' operation).

Basically, flickering lights are fairly common and on last years Treffen there was a sufferer and at the time i was unsure of the exact method (although i did know the principles). Hence the 'thorough inspection' a short while ago.

It is possible the design was revised (maybe Dieter can illuminate? (bad pun!)), Scarlet is an early F after all.


Mines a 'P', so still early- curious.

Will Munns

Hmm, very odd. The switch on my car is definitely below the pedal. Depression of the brake pedal releases the pressure from the switch plunger, thus turning the lamps on.

Mine's a 95 build, 96N registered car
Rob Bell

Where does the "revised" switch fit?

Mine's a P reg too, and it too is below the pedal. Its one of the "originals" with the pull-out-able rods.

When it is "depressed" the lights are off and when released they are on.

(I recently had to do the "screw mod" to mine as it looks like I'm fresh out of adjustment - but now its fine again).


>Where does the "revised" switch fit?

Same hole as the old.
Lot's of confusion and I think only misunderstandings regardinfg OFF and ON and release or press.
I kept off here since Will's first disagreement :)

I swear:
There is no change since the car was introduced until the MY2000 came out with the revised new switch and attachment. (Switch turned 180 and tab to access revised at the brake pedal)

MK1 switch location

MK2 switch location
Both work in the same manner, though.

All please down into the footwell and check again ;)
The switch pulls to (+) if you hold it free in your hand.
And (+) switches the brake light. The is unique at this car, cause all other switch to ground.

I bet a bunch of beer cans on it :)

Dieter Koennecke

Yup, that's what mine does Dieter - switches on (+) when the plunger rises when the pedal lever is depressed to apply the brakes (so would be on (+) when removed and in your hand). I'm sure we are describing the same thing here?

Bloomin' difficult thing to get to - as your photographs show ! Involves all sorts of cortorsions in order to get under the steering wheel! LOL
Rob Bell

>all sorts of cortorsions in order to get under the steering wheel!

LOL, thats why the pictures are so bad ;)
I'm looking foreward the next 'driver practicing course' with several MGF newbees on June 2nd. I bet they will all have the brake light trouble after they have practiced 'hard braking'.

LOL will be a sporty day again.
Dooh, my poor back ;)
I'm sorry, only in German language. Just click the links to see what's going on there.
Known as 'skid training' IMO from similar places in the UK.
To recommend for each driver !!

Dieter Koennecke

This thread was discussed between 13/05/2002 and 22/05/2002

MG MGF Technical index

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