8 replies to this topic

[neiloliver]

Hello,

My 1975 mini 850DL failed its MOT today because the brake lights were not working

Bulbs are OK.

I have 12V at one of the terminals to the hydraulic brake light switch and if I short the two terminals together the brake lights come on OK.

The switch is therefore suspect.

However, I found that if I really stamp on the brakes hard I can get the lights to come on. So I am wondering - is it the switch itself or do my brakes need bleeding? The brakes DID pass the MOT but only just (but hey, it is drums all round and she is 37 years old so what can you expect!)

Does any one know if this is a switch problem or a brake pressure problem?

I think the switch is this one:

http://www.minispare...|Back to search

Thank you for your input
Neil

[Carlos W]

Firstly, this is based on my theory, and not fact, so please understand my uncertainty

If you press really hard on the brakes the amount of pressure on the switch will be greater, if there is a fault in the switch, it may require this amount of pressure to make it work!

My advice would be to replace the switch as I think that's what the fault is!

[KernowCooper]

As said the switch is only making contact under extreme pressure so a internal fault is present in the switch a new switch would effect a cure.

[Ratkiller]

Yep, it's the switch.

[neiloliver]

Thanks for the triple answer. I will get a switch and swap it out. I tried to get my largest socket on it (15/16") and it does not even come close.. I don't suppose any of you know what size it is?

[tiger99]

Best to measure it with a steel rule, or a vernier calliper if you have one. I recall using one of my larger open-ended spanners, so it might have been 1 1/4" or 1 5/16", but I can't be certain as only my very first Mini had that type of switch. Most sockets are not really useable because of the terminals, unless they are unusually deep.

[lrostoke]

A fix that worked for us was fit a relay in the circuit.

We replaced the switch first but found that the brake lights got brighter the more pressure you put on the pedal. With the run of bad parts around probably a dodgy replacement switch.

We changed it so the brake switch activates a relay which then sent power to the brake lights...the relay activated at lower voltages so brake lights now come on whatever pressure we put on pedal.

Just found this

http://www.gomog.com...ightswitch.html

It's for Morgans but seems they use same or similar switch and theres a bit at the bottom about fitting a relay to take the load off the main switch.

Edited by lrostoke, 28 March 2013 - 10:16 AM.

[PaulWright]

My old pressure switch required a 1 and 1/16 inch socket (i think) although the replacement unit was smaller. My old one wouldn't budge and the torque I was using was putting at risk to the brake pipes down on the subframe.

Inspired by
http://www.scottishm...ke-light-switch

I fitted an electrical brake light switch in parallel with the faulty pressure actuated switch. Went for the electric switch – power epoxy into position using a multimeter to bleep on/off to get the set point. Hold with bulldog clip whist the epoxy dries.

[neiloliver]

Update:

I purchased a C16062A switch from 'mini-mine' in stoke yesterday. The old switch was 1" AF and turned with moderate torque applied. I had already put a poly bag over the filler of the master cylinder and replaced the cap (like it says in the Haynes manual) and I had the new switch (22mm AF) ready to make the swap.

However, when I lifted up the unscrewed assembly there was another part attached to the end of the switch.. I think it is called a Banjo bolt? Anyway it took me ten minutes with WD40, a machine vice, a bit of swearing and a spanner to separate the two but they came apart and I was able to replace the assembly.

I cleaned up the little bit of split brake fluid and tried the brake.. it worked, the brake lights came on :)

I also had to replace a front side light and fix the OS steering gaiter clip.... and I hope to take it for re-test tomorrow... fingers crossed... That is assuming my brakes do still actually work :)

Thanks all for your advice.

Neil