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MG Midget and Sprite Technical - Constant brake lights

I've searched the archives and can only find mention of non working brake lights.
My problem is the opposite in that brake lights are on constantly.
What is more likely, a short somewhere or some problem with the pressure switch.
Has anyone had this problem and how was it sorted?
Thanks in advance.
G Lazarus

Try pulling the wires at the switch, if the lights go out its the switch - if they stay on its a short somewhere.
Mick - The engine is in!

Like Mick says!
Dave O'Neill 2

Or do they go off when you pull on the handbrake? If so it's the small return-bleed drilling in the master cylinder that's blocked.
dennis
D Stanfield

The problem and it's cure depends on the year of your midget. If it is an early car, with a hydraulic switch, it is either a shorted switch, a short somewhere else in the system or hydraulic pressure that hasn't been released. If the car is a later version with the switch on the pedal box cover, it is either a shorted switch, a short elsewhere in the system or a misadjusted switch. The first check to do, regardless of the year of the car is to unplug one of the wires from the switch. If the brake lights go out then there is not a short elsewhere in the system. Next, if the switch is hydraulic is to open a bleed screw from one wheel cylinder and see if the brake light goes out. If it does, then you have a hydraulic problem that needs to be rectified. If the light does not go out, then the switch is shorted and will have to be replaced.

If the brake light switch is a mechanical switch on the pedal box, loosen the jam nut and try screwing the switch in one or two turns and see if this turns the brake lights out. If it does, then just tighten the jam nut down and you are good to go. If it doesn't shut the brake lights, you will need to remove the switch and see if the plunger is worn down to where it doesn't press against the spring in the switch (brake lights should go off when the plunger is pressed in) or if the switch is just shorted (won't turn off regardless the plunger is). Either way the switch will have to be replaced.
David DuBois

Thanks for the advice.
It's a Frogeye with a 1275 pedal box, so I'll try to have a look when I get home tonight.
I suspect bad wireing.
G Lazarus

Gary - on the inner wing left hand side there will be a brass plug with 2 connectors (it might have 2 wires on each connector). Thats your brake light switch so disconnect and see if they go out...
Toby Anscombe

My money is knackered pressure switch. Try the friendly persuader on it. They can stick on.
Dean Smith ('73 RWA)

Gary, that's easy, you live and work in London, it's normal!

If you watch very carefully you will see them going off for brief periods of time.
Jeremy Cogman

just around now someone is going to tell Gary that he needs a relay to stop the new switch (that he is going to have to buy) from arcing out internally


So I thought I'd do it...

unless there is a fairly terrible short circuit somewhere it almost definitely has to be the switch internals sticking*

if pressure had built up enough for your brakelights to stay on, within the hydraulics, I would expect you to feel the stoppers on all the time now

'cos while you are running in the loss of power would be very noticeable during your low revving use cycle

*test?

easy

the wires on the stop lamp switch are green (in) and green/purple (out)

first take off the green wire

if the lights go off it is most likely the switch

if the lights do not go off there is a short circuit somewhere between the switch and the tail lights, feeding the stop circuit from elsewhere (a powerful possibility if this is the case is the knot of bullet connectors on the top of the driver's side A post panel, two bullets partially pulled out of their tubes can cause the symptom) the tail lights on Midget/Sprites at least travel together down the inner sill after joining up under the dash board

After this all the wires should all be dead, unless switched on, right back to the back of the car.

Kind of cuts down the places where it can short out

the only live wire to the back is the fuel gauge (I seem to remember that you had an issue with this a few weeks ago, was it your car?) but that also gives you a good chance of finding the fault if it isnt the brake switch


Oh blimey isnt this a long bit of waffle?
Hope it helps a bit
Bill

Gary, have you tryed getting your foot of the brake pedal?
Its not good for the car to push the accelerate+brake pedal at the same time! LOL
Arie de Best

Arie

he is running in
surely he needs to stay slower when he is doing that


:-(
Bill

<*test?

easy

the wires on the stop lamp switch are green (in) and green/purple (out)

first take off the green wire>

Bill, you forget which car we are talking about and others may wrongly assume that the wires are different colours. They are most probably all the same colour wires. Why should that part of my wiring be any different to the rest of the wires in my car. But I'll check anyway.
The car had been in very solid traffic for the last five miles of a 60 mile journey (basically the London part of the journey) and it was stop start traffic, alternating from neutral all the way up the gearbox to FIRST gear. So I'd also had the fan on for some of the time.
I don't know what relevance that useless information has but I thought I'd mention it anyway.

I will check and report back.
G Lazarus

This thread was discussed between 28/09/2008 and 29/09/2008

MG Midget and Sprite Technical index

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