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MG Midget and Sprite Technical - Brake pressure switch

finally....the brake pressure switch on my MkIII has given way [acceptable performance for the 47 years of ownership...] but I have heard that "new" ones are notoriously unreliable....has anyone any experience of repairing originals? Many than, as ever...Dave
David Cox

David,
I believe the old VW Beetle switch is a good fit for a midget.
VAG part number 113-945-515-H.
I’ve not tried it as I already had a spare when mine failed last year.
Simon
S Holt

If we are talking hydraulic switch here then the Volkswagen switch requires an adaptor.

Use a Harley-Davidson switch as per photo.

With preparation and speed the switch can be swopped without the need to bleed. Changed one, once, in a car park in Florence, Italy, after the old one failed in the on position.


Alan Anstead

thanks!
David Cox

I'm not sure you need that much speed, I've changed three times that I can remember, and I'm not fast with any car work!
Nigel Atkins

As with any temporary hydraulic system disconnection, a piece of polythene under the reservoir cap stops leakage whilst you fit new parts like brake light switch or bleed nipples. If air cannot get in at the top, then fluid cannot drain out at the bottom!
GuyW

Guy

Never heard of that one but it sounds a perfectly credible and splendid idea to me! Does it work?
Oggers

Yes, I do as Guy suggests with cling film under the cap. Get ready with the new switch when you take the old one out. Hold your finger over the hole while you get ready and screw the new on in sharpish. I got a new Quintin Hazel switch from Euoroparts (I think). Its still OK 3 years on.
Paul Hollingworth

Cling film under cap and wet rag under switch union, I didn't bother getting my finger any messier.
Nigel Atkins

Yes it works well Oggers. Either secure a bit of film or plastic tightly over the filler hole with an elastic band, or by fitting the cap over the film. And actually it retains the fluid very well so you don't really have to hurry too much either. I have left a system like that overnight and although it did need bleeding it had only lost a few drops of fluid.
GuyW

I should have mentioned the clingfilm or an old carrier bag. Works also for changing a slave rubber, with the slave still in situ, whilst under a car somewhere in Europe.
Alan Anstead

I think the drive to somewhere in Europe is optional. I have found it works pretty well in other countries.
GuyW

The U.S. version uses a mechanical switch instead of a pressure switch since it is dual circuit. The replacement mechanical switches are also very unreliable. I installed a relay for the brake lights and the low current has added life to the replacement.
Glenn Mallory

Glenn,

The earlier Spridgets with a single line brake system had the pressure switch. When they went to the dual line master, they change switches.
Martin

Yeah, the mechanical ones aren't much better, even with a relay. Just been doing my yearly winter rebuild of mine!

Top tip (maybe?) for mechanical switches. The metal part contains just the plunger, the black plastic part the actual switch/contacts. Open up the switch by bending open the crimped edges on the metal part and seperate the black plastic part from the metal part, then reassemble it with cable ties but don't re-crimp the metal part.

When the switch enevitably stops working, you can snip the cable ties and remove the black plastic switch part to clean the contacts without having to disturb the pedal box to get the whole switch out.

Fiddly, but better than the alternative IMO.

Malc.
Malcolm

This thread was discussed between 12/02/2022 and 15/02/2022

MG Midget and Sprite Technical index

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