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MG MGB Technical - Brake light switch

I'm so tired of fooling around of the POS replacement brake light switches offered for sale for the late MGB's. They only last about a year before the internal contacts burn enough so that the lights won't work. Does anone know of a replacement switch that will fit in the same position as the original, but work?
Jimmy P

Try taking a glance inside of a napa or o'rielly's store Jimmy, they usually stock brake light switches on classic cars, I'm betting that a little searching in their stock and you'll find one of the right size, shape, connections, and hopefully color as an original switch.
CJD Dark

Jimmy - YOu got a year out of the replacement switch? What's the beef? I only got two weeks out of the one I got. Seriously, what you need to do is install a relay and arc suppression circuit in the brake light circuit, then the whimpy switches will last just about forever. Go to: http://www.omgtr.ca/technical/brakelightrelay/brakelightrelay.htm
for information on how to meke and install the relay and arc suppression circuit. It is best to install a new brake light switch at the same time you install the relay as old switches can have burned contacts that will have a high enough resistance to cause the relay not to operate correctly. Good luck - Dave
David DuBois

Thanks, David, I will try your relay system on my new V8 project. With any luck I'll save some money.
Jimmy P.

Jim,

You might attempt to use this brake switch driving a relay, this way you decrease hign current into the switch points itself, leaving power to the switched relay contacts. But, remember not to forget the drain diode connected in a parallel way on the relay coil, similarly to one SU fuel pump connections.
kind regards.
Renou

Although I haven't tried it, I would think LED brake light "bulbs" would prolong the life of a switch, as I'm sure they have a much lower current draw (and more importantly, don't cause the initial surge of current that incandescent bulbs cause.)
Rob Edwards

Rob - The LED brake lights is the ideal answer for a number of reasons. Unfortunately, none have been perfected yet that can be used behind a lens that gives the coverage that the incadesant bulbs do (ie. they become rather directional). If they are ever perfected at a resonable price (the ones used on the big trucks are nearly $100 each), they will be a tremendous boon to old car drivers.

Renou - If you check the web site I included to Jimmy, you will see that a diode is indeed placed across the relay coil, in addition to a capacitor across the switch contacts to for an arc supression circuit.
Cheers - Dave
David DuBois

DAve,

Nice web site very end user friend. From my own the diode must be enough to consume extra current . But
your 2 solutions are OK and capacitor is a maximum
protection . In fact , I'll keep my 64' brake switch as long as it works finely, and modify the wiring your way for further reliability.
- regards-
Renou

Renou - No need to go to the relay and arc supression until such a time as you replace the switch. In fact, I ran into trouble putting the relay in with a used switch. There was enough burning on the switch contacts to build up enough resistance that the relay would not energize until I replaced the switch. Since then I have recommended that the relay and arc supression circuit and a new switch be installed at the same time.

I can't take credit for the web site. That is the site for the Ontario (Canada) MG 'T' Register (I live in Washington State USA on the other coast). Their web master has included a number of my technical articles on their web site.
Cheers - Dave
David DuBois

Red, white and amber LEDs are becoming quite common on buses round here, even as replacement on old buses. The red perform both tail and stop light functions by switching 3/4 off for the tail light only and dimming the remainder. Not noticed directionality problems, I'll have to look, but should be less of a problem for brake lights I would have thought.
Paul Hunt

Paul - I was refering to LEDs behind lenses such as the ones on our MGBs causing the LEDs to be directional. I agree that the ones being used on trucks are not directional and quite effective, but I don't think they would look real good on our cars. Cheers - Dave
David DuBois

Check out the MGB General Thread: Looking for Blue Dash Light! for more info on LED lights.

FWIW

Larry

Larry Hallanger

This thread was discussed between 28/02/2004 and 01/03/2004

MG MGB Technical index

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