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MG MGB Technical - Brake light switch

I just read the archive on Brake Light Switch problems, but have another question. My 72GT has the brake light switch on the cowl covering the brake and clutch master cylinder. I took off the switch and it measures on the ohm meter be be a normally close switch. Is this correct, or is the switch defective.

I can't get the switch adjusted correctly. Either the brake lights are on all the time, or I can't get them to light at all.

Is the brake pedal suppose to depress the switch to complete the circuit, or release the switch to complete the circuit.

I've looked every MG manual I have (3 or them), and can't find any information.

Thanks,
Dave
Dave Shively

The switch is opened by the pedal returning to the OFF position. Install the switch and turn it in until the lights come on then back it off a turn or two. This will give you enough play so that the switch is in the off position until the pedal is partially depressed allowing the switch to close and thereby turn on the brake lights.
Sandy Sanders
conrad sanders

Dave - The switch is a normally closed switch and it opened by the released brake pedal resting aginst the actuating rod as Sandy stated. If the switch is screwed in too far, it can actually hold the brake pedal down a bit and can conceivably keep the brakes applied partially. I normally screw the switch into the boss on the pedal cover, while checking with an ohmeter until I see that the switch is open. Then, leaving the ohmeter leads connected, back the switch out until the switch just comes on, after which I turn it in until the switch opens. At that point, I give the switch about a half a rotation more in the IN direction and lock it down with the jam nut. Hook it up and check your brake lights, they should go on and off as you press and release the pedal. Good luck - Dave
David DuBois

This thread was discussed on 13/12/2004

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.