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MG MGB Technical - Break light switch

'69 MG. The break light switch that operates off the back of the break pedel, does any one know how to keep these working or a good replacement? CAn they be taken apart and fixed? These surely have not proven relyable and don't last two years. The little buttom goes in and out but doesn't operate.
Thanks, Geoff
Geoff Kimler

Had one in my current B a decade. Maybe try some carb cleaner shot down into the button. The only thing I can think of is the contacts inside getting dirty. Never tried to take one apart, but if you could you could clean the contacts with sand paper, and reassemble. Worth a shot if it's broken anyway.
John A

Geoff - The problem you are dealing with is lousy replacement switches. All of the ones that I have seen are so flimsey they wont even handle the current for a flashlight. If you can get ahold of a NOS Lucas switch, it lhoule last better. The other alternative is to put a relay in the circuit, like I did several years ago. I haven't had a problem since. If you will send me your e-mail address, I'll send you a drawing and write up on installing a relay in the circuit. A local club member is coming over this morning so we can install a relay in the brake light circuit of his MGA. Good luck - Dave
David DuBois

I did both things David mentions (OE switch + relay circuit) and the system seems really bombproof. Plus you get brake lights that are a bit brighter. I wondered if the relay would throw in the towel prematurely clicking on and off so often (i.e., most of the relays in cars don't switch on/off too much), so I found a really high quality relay (you can spend from $2 to $20 on your basic Bosch-style relay) and it's perfectly fine.
David D.

Geoff is right about those replacement switches. My own autopsy testing with an Ohmmeter revealed
that the switches become fouled with carbon and dirt and exert an inconsistent amount of resistence across the contacts that is just enough to prevent the lights from coming on. The switch is located
inside the engine compartment on the same side as the carbs and exhaust manifold and is no doubt
subjected to all sorts of heat, vibration, dirt, fumes, etc.

A simple fix for this is to install a more dependable (and cheaper and more plentiful ) brake light switch
from a '69-'74 Chevy Nova or Camaro. You'll need to fabricate an "L" mounting bracket and bolt it next
to the brake pedal arm, inside of the legwell. The wires are routed through the bulkhead using the
same route as the choke cable and are connected to the stock brake switch wire harness connectors.

A self-pick parts wrecker yard charged me $6 for several used switches and I have not had a failure
since I put the first one on a few years ago. The brake lights also shine slightly brighter.

You need to retain the original brake switch as it also functions as a pedal arm free-play adjuster.

I can email you photos of this mod if you provide an address.
Daniel Wong

Thanks, Guys. Here is the e-mail address, pictures would be appreciated, Daniel. These are Lucas switches I have been using, weather they are of early manufacture I don't know. I have found Napa has some switches at half the price of Moss.
The switch being screwed into the pedel housing should be protected from grit and stuff but the little button just doesn't seam to be roubust enough. Maybe the contacts do get welded together. I will have to take one apart.
Geoff
Geoff

Geoff,
Also have '69 B and would like to stay in touch re: exactly how things are set up on our year cars. Also, when I replaced my brake master cylinder had to dis-assemble the system, the switch wouldn't work. Ordered a new one but have never installed as after replacing wiring and tweaking with exactly how far it is screwed into the pedal box it started working again. Nice to hear about the NOS being much better. Let us know how this turns out if you take switch apart.

John Bamford
John Bamford

I went the American switch approach years ago at the pedal. Still found I was taking the switches back to NAPA under warranty. Not to mention my wife driving around with no Brake lamps. I tried a Genuine Lucas switch for a TR6 and have had no more problems. Much better quality then the cheap "twain" american switchs!!! Bob
Bob Thompson

I'm so happy to hear that others share my experiences. My 1969 MGC had the original brake light switch last 25 years. In the last five years I think I've replaced it 4 times. The first few replacements I purchased from VB appeared as original with an oblong shape and could actually be pryed apart and "dealt with" if you wanted to. The last one that failed was a completely odd brass bolt-like looking thing that there is no hope of opening and getting operational again. I have an electrical backround but never thought of the simple relay installation suggested above. Thanks for the revelation. I will fix it that way once and for all!
Kelvin Palmer

Hi

Make sure that the pedal box cover is securely attached to the bulkhead. If it is not then it will move (box,switch & everything ) without the switch button being depressed enough to activate the switch.
Anothe good idea if you are fooling around in that area is to make sure that the clevis pin is in good condition - no scoring and the pedal ends,both clutch and brake, (where the pin goes through) have not been ovaled which leads to a lot of slop in the pedal controls. If the pedal holes are enlarged take the pedals out and replace them or have them bushed.

Alan
Alan

Being basically cheap and a DIY type of mechanic/technician, I took another approach to this problem with the lousy aftermarket switches.

In my case, I had a Lucas OE switch that no longer switched because the push pin that activates the switch inside had worn to a point where it no longer stood out from the body of the threaded housing that holds the switch to the brake linkage cover. Because of that, it would not move far enough to operate the switch.

I kept that switch and went through a couple of the aftermarket units in fairly short order, maybe a year apiece. After the second A/M switch died, I took a look at the OE switch and did two things to make work again.

1) I drilled a very small (3/64") hole in the bakelite/plastic back of the switch and into the interior, just to the side of the round cylindrical projection there. I did this to more effectively spray in some contact cleaner into the body of the switch and (hopefully) clean up the muck around the contacts. When the cleaning/flushing was done, I simply filled the little hole with a dab of silicone sealant. That seems to have worked very well.

2) I then took my Dremel MotoTool with a cutoff disc on it and very carefully cut back the threaded collar/body that holds the activating pin. I removed just enough (about 1/8"-3/16") to provide a new exposure of the pin, hopefully enough to keep it operating for a while. After that, I reinstalled the switch, lubed both the pin and the brake arm it rides on with some Teflon grease, and it has since served me reliably for some yrs beyond what it had previously.
Bob Muenchausen

Great tip Bob! I am glad I saved my old switch. Like yours its only problem was that the pin was worn.
Andrew Blackley

This thread was discussed between 25/02/2003 and 27/02/2003

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