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MG MG Y Type - YB brake lights

On my YB which is fitted with a hydraulic brake light pressure switch just behind the master cylinder I find that the brake lights don't come on unless there is firm pressure on the pedal. Is this normal - the braking system has been checked and is fine (MOT). The upshot is that gentle braking does not operate the rear brake lights. Is this due to the pressure switch needing a certain pressure to make the connection - does it indicate a new brake pressure switch is needed?
Any one else has this problem?
David Mullen

Hi David,
I used to have a similar problem on my 1969 MG Midget, until I learned that there was a difference between a brake light switch for a Mini and a brake light switch for a Midget.

They appear identical, but one switches at 15psi and the other at 7psi.

If the brakes are well adjusted and the car driven with care, about 10psi is all a rear wheel drive car needs I was told (probably 20 years ago).

The issue if you use silicone fluid adds to the problem.

A brake light switch from a Harley Davidson Motorcycle is designed for use with silicone fluid and switches at 5-7psi. It has the same thread as an original Midget switch (taper gas), which I understand is what the Y-Type conversion kit from the register uses.

I am about to convert my YT brake light switch to hydraulic operation using a Harley switch. The Harley switches are twice the price of a "normal" switch here in Aus, but they last 3-4 times longer.

It is my experience with the Midget (owned for 15 years), that unless you drive your car every few days, the brake switch will start to stick after a few years - maybe that is your issue ?.
Tony Slattery

Gentlemen - The silicone issue is is BS, in a hydraulic brake light switch, the hydraulic fluid acts against a diaphragm and never comes in contact with the switch contacts. The whole problem with replacement switches is that the replacement switches available today are crap - they are so light duty they don't last more than a couple of months (I had one MGB mechanical switch, which by the way, never comes anywhere near the brake fluid, silicone or otherwise, fail in two weeks!). The first indication of switch failure is excessive pressure on the brake pedal to get the lights to come on. There are two different fixes for the problem - 1) get on of the heavy duty switches from the Ron Francis Wiring company at: http://www.ronfrancis.com/showpage.php?page=main.htm or 2) make up and install a relay/arc suppression circuit as described in the article, Brake Light Relay on my web site at: http://homepages.donobi.net/sufuelpumps/ Cheers - Dave
David DuBois

The original mechanical one is still operational on my YB. If I was to replace it, I would use one of a scrap Metro where the pedal works the unit not brake pressure, then when you touch the pedal, you get brake lights. Ideal to warn that tailgater.

NC.

If you want to remain original, then use the motorcycle brake light switch as sold by ARMOURS.

Neil Cairns

This thread was discussed between 22/06/2008 and 23/06/2008

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