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MG MGB Technical - Brake light switch

I hope someone can refresh my memory. My brake lights tend to stay lit even after I take my foot off the pedal. If I use the my foot to pull the brake pedal toward me, they go off. Clearly the switch is engaged too much.

So to readjust the switch so it's not as easily engaged do I turn it clockwise or counterclockwise in the pedal box cover? Thanks.

Dan Hiltz

Looking from front of the car turn it anti (counter) clockwise.
Chris at Octarine Services

Depends on the year, prior to the boosted dual servo system the switch was on the front of the pedal box, then it was moved to the rear.

To turn the lights off the switch has to be screwed in more, as it is a normally closed switch which closes as the pedal is operated, and opens to turn off the lights when the pedal is released and the switch plunger is depressed. Under those circumstances the switch has to be screwed in to the boss, and it is a normal right-hand thread.

It's quite a precise adjustment, if it is screwed in to far it can stop the brake pedal coming all the way back which can cause the brakes to be stuck on when the fluid gets hot and expands. The book says there must be 1/8" of free-play at the pedal pad, but free-play to what isn't mentioned. On mine (front of pedal box) there is only one and a half turns between the lights staying on and the switch starting to depress the pedal, so I have set mine 3/4 of a turn in from the lights just going off.
paulh4

ThankS Paul. It's a '74 with the switch on the front of the pedal box, and since the switch is above the pivot of the pedal, it makes sense that turning the switch in will increase the amount of contact with the pedal, thus keeping the circuit open.
Dan Hiltz

Has anyone tried these (from eBay)?

Dan Hiltz

Dan. It may be the brake light switch needs to be adjusted. But, when you post, " If I use the my foot to pull the brake pedal toward me, they go off." might well indicate that the problem is in the brake pedal spring located under the dash. There is a spring to return the brake pedal and a second spring to return the clutch pedal. When these are missing, broken, or have stretched too much, the allow the brake and clutch pedals to dangle unrestrained and cause problems similar to what you report with your brake light not going out until the pedal us pulled towards you. I would check the springs first, then move on to the switch adjustment.

As to the Lucas brake switch, I have seen parts labelled "Lucas" that were listed as "Made in the UK" and which worked quite well. I have, also, seen some of them that were real dogs and did not hold up well.

Les
Les Bengtson

That image looks like the standard switch. Lucas only own warehousing now, all manufacturing outsourced to the usual suspects. I hear that the crimping of the can to the body is poor and it can all spring apart. Similarly I've found their indicator flasher units are actually hazard flasher units internally which don't work correctly as indicators.

Good point about the spring.
paulh4

Thanks Lee. The spring is there but it must not be tight enough, because i can pull the pedal back a bit and if the spring were keeping it under tension, that wouldn't be possible.
Dan Hiltz

This thread was discussed between 20/06/2020 and 22/06/2020

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