Hello All ,Which is the correct switch to use the white one that works from the brake pedal or the screw in switch on the brake line ?
TY Allen

Screw in hydraulic switch under the brake servo

While gtogreen is right about the hydraulic pressure switch in line and the original lucas units lasted well, aftermarket replacements are highly suspect and I've had several fail. I have now started to fit a bracket to the side of the pedal box to take the later press switch and run the 2 actuating wires inside the car.
May be worth considering while/if the pedal box is out.

+1 on the poor quality replacements. I bought a replacement hydraulic brake switch from my local "Auto One", lasted about 3 or 4 trips in the car and from memory cost about $30.

I'm thinking the same about fitting a mechanical switch.

I don't know if I've ever had an original fail, but I have a collection of them in my parts bin...

if you have the original, test it, if it works, use it

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did I tell you that I won a trophy?

There's quite a good article about the widespread failure of the brake light switch here - http://mgaguru.com/mgtech/electric/et119a.htm

Clicking on the various hyperlinks in the article takes you to more detailed information. For example, this one shows what they look like inside - http://mgaguru.com/mgtech/electric/et119g3.htm

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ex-NSW Police 1970 MK II Cooper S
VMCI #43

I see - it's an electrical failure rather than mechanical, I thought they might have collapsed internally or something.... they can't handle the current from the brake light globes... as he says in the first paragraph, chucking a relay in would fix it but I disagree with him that it'd add another point of failure.

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did I tell you that I won a trophy?

There are badly made relays out there too!

I don't agree with a lot of what he says. If his list actually worked it would be a good thing, but the suppliers can't be depended on to continue putting the same part in the box.

If the relay keeps a cheap switch working then its a win, despite the added complexity.

I think I'd look at retrofitting a mechanical switch on the pedal, its what the factory did later on, and seems to be what the majority of modern manufacturers do. If it does fail, you don't have to bleed the brakes each time you replace it.

In the mean time, I'll carefully horde my small collection of old ones.

Tim

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1951 Morris Commercial J Type Van
1955 BSA C11G
1961 Morris Mini Traveller
1969 Triumph TR6R
1977 Leyland Moke Californian

pretty sure the pressure switch was retained...

the mechanical switch was put there so the BRAKE FAIL warning light can work - if the mechanical switch is closed (pedal pressed) and the pressure switch is open (no pressure) then no brakes = warning light

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did I tell you that I won a trophy?

The brake fail warning switch is built into the dual circuit master cylinder. In the UK they transitioned from the hydraulic switch to the switch on the pedal in 1976. It may have been a little later here.

The bracket to fit the switch to the pedal and the switch itself cost around $10.

Tim

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1951 Morris Commercial J Type Van
1955 BSA C11G
1961 Morris Mini Traveller
1969 Triumph TR6R
1977 Leyland Moke Californian

I agree. I was hoping for a finite statement about where good new ones can be purchased but it seems to be a list of those that may or may not be faulty. The main reason I posted it was to show that others have recognised the same problem.

Genuine New Old Stock Lucas seems to be the safest solution, if they can be found.

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ex-NSW Police 1970 MK II Cooper S
VMCI #43

Can't you find a good used one? I've never had one fail in 36 years and 6 Mini's. Current one is 51 years old..

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67 Deluxe
Dry suspension
1293cc, 11:1 comp, RE 282 camshaft, 45 Weber, extractors etc
4 synchro close ratio gbox
Cooper S brakes, no booster
Stealth box, as Doc says "goes harder and idles!"
RH tank cos I needed it crossing the Nullarbor etc..