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MG MGA - brake light switch

I have several times had to replace this switch on my minors and think replacement ones currently available are very poor quality. It's easy on the minor but if I have to do this on my MGA it's going to be the very devil because access is obscured by the manifold and carbs on my crossflow engine. I wonder if anyone has changed to an electrical contact brake light switch as used on most modern cars?
H L Davy

I mounted a mechanical switch (BRK 3143 from dsnclassics)on the pedal bracket, which operates a relay, so no load on the switch. The switch is adjustable and i set it to trigger the relay before any braking action comes into effect. The hydraulic switch just 'plugs' the hole in the union.

C Manley

I, too, have had to replace my MGA brake lamp switches several times. My "sparky" friend thinks that the new switches are designed to operate a relay and the full 12volts is too much for them. A mechanical switch is probably the answer but I will keep persevering for the sake of "authenticity"!
Barry Bahnisch

I have gone through 3 Lucas branded brake switches in as many years. They are not easy to replace as twurning the switch tends to move the bracket and hence bend the pipes.
I now wedge the bracket and then use a long extension on a socket to get the old one out, reverse the wedge and then put the new one in.

One comment on the photo. What is the second switch for? It looks that the clutch is also wired in for some reason?

I now also have adopted using the handbrake if stopped in a queue as I think this is a possible time when the switch would burn out.

Neil Purves

HL there's info in archives on this and Barney's site. Its a rotten job but I fitted a relay as per Barney's recommendation to take the load off the switch.
J H Cole

I like the mechanical switch on the brake pedal, but only have it on Triumphs where it was the standard fit.
As well as a more reliable switch and easier to change, the lights come on as soon as you touch the pedal and remove the free play.
It may not seem much but the earlier your brake lights come on the better.

M F Anderson

Thanks to C Manley. (Hesitate to say Mr. in case I get handbagged by some amazon.) That's exactly the sort of thing I was thinking of. Barry - I think it's a hydraulic problem with the switch rather than electrical. Have had it with both silicone and regular fluid.
H L Davy

Neil, I think that the other "switch" that you can see in the picture must be the relay that Colin Manley mentioned that he has fitted in conjunction with the mechanical brake light switch. It just happens to be mounted in front of the clutch pedal.

Colyn Firth

This switch will take care of the problem.

I also did what Barney recommended several years ago and have had no problem since.
CM Harter

Colyn, Neil,
Yep, that is the relay to the left of the switch - keeps all the wiring close together.

No Handbag, definitely a MR.

C Manley

Great stuff as usual by MG enthusiasts. For further info dsn list that switch under minis but not minors, also MG's don't feature! I must say that asking questions on MG and Minor enthusiasts site similtaneously is really rewarding. What relay should one use?
H L Davy

I changed my brake switch from the pressure switch on the hydraulic line to a mechanical light switch positioned on the brake pedal. This change is described in "Tech Sessions from MGA!" by Mike Ash and published by NAMGAR. It is an inexpensive change and it has worked for me for over a decade.
Bill Haglan

Yes, it was a mini switch - i went for it because of the adjustment feature. You should be able to use any 12v normally open contact relay with a sufficient capacity to handle at least 5amps (2 x 12v 21 watt bulbs = 3.5amps)most are well in excess of that. The latest 12v ones are nice and small (about 1" cube), don't cost the earth (about 4 from a motor factor, i recall) and come with a screw mount tag.
C Manley

Agree with CM Harter...the Ron Francis switch is the way to go...have fitted to two MGA's and BGT, and work with very minimum foot pressure. The only difference to the look of the switch is the connections.
Gary Lock

Hey guys, -- I have to step in to defend myself here. I have NEVER recommended installing a relay to save a junk brake light switch, and I still don't. The brake light relay article is not even my work. It is an off-site link to an article with someone else's name on it, clearly labeled "os". The link is on my web site because there has been a lot of interest in the brake light relay, lots of commonly idle chat like you all are doing now, and that tech article just shows how to connect the relay (if you insist on doing it).

My primary comment on that article is, that person must be a real glutton for punishment to insist on using a junk switch and then go to all that time, money and effort to make it work by adding a relay, and then also take the time to publish it and recommend that other people should similarly waste their time and money doing the same thing. And by the way, the recommended 30 amp relay is gross overkill, as well and mention of a suppressor capacitor and a diode. The whole thing is predicated on the idea that we are somehow obligated to use a junk switch from the common sources and never complain or send one back. We are not obligated to buy and use junk parts.

The brake lights only take 3.5 amps, and any decent brake light switch should have no problem with that current level. The rash of switch failures in recent years points to bad manufacture and faulty switches, not a bad application. Not long ago some people were trying to blame the failed switches on the use of DOT-5 brake fluid. My recommendation is to install a good pressure switch, and don't bother with the added complexity of a relay.

The reason we have what seems like hundreds of reports of bad pressure switch is because most of the people doing the complaining don't care about it enough to do the right thing. On top of that, you might think about all the people who aren't concerned enough to even mention it. This is likely because the switch is such a cheap part the people figure it's not worth complaining to the supplier or shipping it back, and they don't even feel the moral obligation to notify the supplier that they are selling junk parts.

If you want to end the rash of bad brake switches you have to complain loudly to the retailer, send the junk back, and demand your money back. If everyone did that the retailers would soon realize the financial losses, then either stop selling the part or find a good one to sell. If the retailer refuses to give refund and/or continues to sell the bad parts, then we need to identify the source of the bad parts, make it LOUDLY public, and refuse to buy the junk from that supplier. It is hard to believe this has been going on for so many years, and people are still buying crap switches, then spending more money and time to install a relay trying to make the junk switch work so they don't have to send it back or bother to find a good one.

Now after all that ranting, I would like to remind everyone that there is a special section on my web site dealing with "Faulty Replacement Parts". See here:
I would be happy to create a new web page specifically for the faulty brake light pressure switch. The primary reason this does not already exist is because of all those complacent people who like to complain in public without doing anything about it. The other reason is because I have had exactly one failed brake switch in 25 years and 240,000 miles of use, so I'm not even sure the problem is real (with tongue in cheek).

Now if anyone wants to do something constructive (other than bitching in public to no avail), then let me know the source of your failed brake switch, when you bought it, when it failed, about how much time and how many miles in service. Before I post it as a faulty part, there is the obligation that you must report it to the supplier, and let me know the content of the response. If they acknowledge the bad part and do something reasonable about it, then the problem is gone before I can record it, and it doesn't need to be recorded. If they refuse to acknowledge that the part is faulty part, and they continue to sell the bad parts, then I will be happy to lay it on with both barrels.

Procedure then is for me to record the circumstances of the faulty part on a public web page, naming the supplier of course, so the supplier has a chance to respond properly. I would also like to note the name of the person reporting the bad part. That name does not have to be made public, but I have to know in order to "negotiate" with the supplier. If we can't prove that there is a bad part, and there are no returns, then the supplier has every right to believe that the parts are all good, continue selling the same parts, and may refute the content of my web page.

So if you are not prepared to make all the right moves, don't bother calling me, go ahead and use a relay if you like but please stop complaining in public about your personal non-issue. If people will report the problem to the supplier, and then to me, I can tabulate every legitimate complaint made known. I can also record happy people with good switches and note the names of those suppliers as well.

For anyone who has had a switch fail prematurely, I suggest you buy an Echlin switch from NAPA, and follow up later to let us all know if it is a good or bad part. I have no idea if the Echlin switch will be good or bad, but it is a suggestion of a place to start when looking for a different supplier who might have a good part.

With all due respect to everyone,

Barney Gaylord
1958 MGA with an attitude
Barney Gaylord

Another heads up - My friend has just had trouble sourcing the correct brake light switch for his ex-South Africa 1959 coupe. One from Brown & Gammons , one from Moss and another from another factor all had a UNF thread and did not fit - all returned. Eventually Brown & Gammons supplied one meant for an MGC that had the correct thread.
Cam Cunningham

That's interesting Cam, I thought it was a standard fitting on a lot of cars of the period!
N McGurk

there are at least two different 4-way pieces around, having different thread for the switch. You will not know if the part in your MGA is original after all those years...
switches are also plenty.


Yes there are 2 types of 4 way union I believe and I think they are tapered BSP thread and parallel BSP thread or could be something else simply have not done any research.

I totally agree with Barney as I have not had a hydraulic switch fail in more than the last 25 years on both my MGA and my midget, maybe I am lucky.

Robert (Bob) Midget Turbo

This thread was discussed between 17/01/2012 and 18/01/2012

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