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MG MGB Technical - Brake lights don't work

I am working on a 72 MGB and all the lights worked until yesterday. Suddenly I had no brake lights. Any ideras what is wrong?
Highlandrocker

If it's not been worked on for a while remove, check and clean all the fuses and the brass fuse holder clips. Refit good tested fuses with a smear of vaseline on their caps. Check stop switch and connections. Check GP wires, bullets, and large common earth connection in boot. Rich.

Rich

Thasnks Rick
I will give it a shot!
Highlandrocker

If only the brake lights quit, fault might be in the brake light switch. Unscrew the switch from the pedal box cover and clean the end button where the pedal contacts the switch.
willie

Thanks Willie. Much appreciate the tip!
Highlandrocker

Before unscrewing the brakelight switch you can just unplug it and short out the wires to see if the lights come on. I have had a brake light switch go high resistance on me rather than fully faulty. I can't remember if you need the key in the on position or not for the brake lights. I've made that mistake before, trying to figure out why it wasn't getting any power only to realise the car needed to be switched on!

Simon
Simon Jansen

Hi there,

My 1970 BGT brakelights were working fine until recently, when I noticed that i had to press the pedal harder and harder for them to come on over a period of a few weeks. Now they're not working at all! The back lights still work fine when my headlights are on.

Bit of a novice I'm afraid, but feel like this is just something that needs adjusting and have some tinkering time at the moment so any clues would be greatly appreciated! First check will be as suggested by Willie above.

Cheers

Bill
Bill M

Bill - I think the US model had a mechanical brake light switch rather than the hydraulic one on our UK models, and so you won't find the switch attached to the pedal box cover as Willie suggested. Look at the right hand wing, under the bonnet, and you'll see the switch screwed into a hydraulic line connector. Bridge its two wires together as Simon says, and if the brake lights come on OK (with the ignition on) then the switch is dead. Its easy to unscrew and screw a new one in - you shouldn't even have to bleed the brakes aftwerwards.
Miles Banister

Miles, thanks a lot, did as you suggested and the lights came on when I bridged the wires. Looks like the switch is dead then! Will get right onto it,

Thanks again

Bill
Bill M

Bill - YOu may find that the replacement switch won't last very long until you have to replace it again. It seems that the standard replacement switches are very wimpy things that don't stand up to the current draw of the lights or the arcing when the switch opens or both. If you find this happening to you after replacing the switch, see my article on making and installing a brake light switch relay and arc suppression circuit at: http://www.omgtr.ca/technical/brakelightrelay/brakelightrelay.htm
Good luck - Dave
David DuBois

This thread was discussed between 29/05/2005 and 02/06/2005

MG MGB Technical index

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