Brake light switch problems

[nwxh]

The brake lights are working (tested while shorting).

The brake light switch records reduced resistance on the continuity test when the brake is pushed but not it never fully closes. Hence the lights never go on.

Is it likely to be the switch packed up or air in the brake system?

I topped up the brake fluid to the rim and pumped up the brakes a lot, but still no improvement.

(Switch is with spade terminals. If it's a dodgy new one I'm willing to replace anyway.)

Many thanks,

Nick

[bmcecosse]

It is a failed switch - bad news is the 'new' replacements don't seem to last 10 minutes.... Look for a good old one....

[bmcecosse]

Found this on an earlier thread ' Had this problem last year, raised it on another thread and got one from this supplier http://www.autoelectricalspares.co.uk/l ... -158-p.asp
you'll notice the terminal molding is different from the ones that fail. mines being on since Jan 14 and still going strong and it's in daily use '

[nwxh]

Ordered, cheers!

[mike.perry]

Replace the old switch and bleed the system of any air if necessary
Jack the car up, remove the o/s wheel and switch and lower the car until the brake fluid is level with the top of the pipe and then fit the new switch. This will prevent any air getting back into the system

[bmcecosse]

Press the brake pedal hard. Put some rags round the switch - unscrew it and pop a finger over the hole till you get the new switch ready - then just screw it in, and mop up any fluid. It's unlikely to need any bleeding. The 3 psi retained pressure will see to that......

[nwxh]

Many thanks.

Unfortunately the switch is seized in and so I will need more tools. What are the ideal tools for dealing with this and should I try and pull the union out of the car or leave it in place?

Should the new switch have anti-seize grease?

Cheers,

Nick

[bmcecosse]

It's always going to be tight - you will need to hold the fitting somehow - and a good fitting socket on the switch. Try to do it in place - otherwise it's messy and complete brake bleeding required of course.

[nwxh]

Mole grip beneath the switch? Seems like it would just slide, or does the wedge a socket approach work?

Will order a 1 inch AF socket, as I'm missing this from my tool kit.

[nwxh]

Any tool(s) which might hold the union I'll get.

[nwxh]

Ok the socket method didn't work, because the metal the socket is pressing against is bending. It looks like I can put a clamp either side of the floor by the union as there is a large hole near by. Will this work?

Otherwise, I assume new union, hydraulic fluid everywhere, and bleeding at every wheel?

[bmcecosse]

That's it I'm afraid. Put a plastic bag under the lid of the master cylinder cap to minimise leakage.

[nwxh]

Thanks. I'll try the clamps and see if that works.

Otherwise I'm worried that everything involved in bleeding will seized and so replacing the union will involve replacing the the whole system.

[panky]

Has no one tried a micro switch under the pedal instead? Save all the faffing about with crappy replacement switches

[bmcecosse]

What 'clamps' ??? There are no clamps involved!! DO NOT ever clamp flexi brake pipes !!!!!!! And in this case - it wouldn't do the slightest good anyway.........

[nwxh]

What 'clamps' ??? There are no clamps involved!! DO NOT ever clamp flexi brake pipes !!!!!!! And in this case - it wouldn't do the slightest good anyway.........

Sorry the clamps would go next to the union to stop movement and pinch the engine bay floor.

[bmcecosse]

Ahhh right......sorry. Worth a try I suppose!

[nwxh]

Best I can think of. Have ordered some release oil too, and will try the mole grips and socket again first after the oil has hopefully done its job.

[bmcecosse]

Since you don't care about the old switch - you could apply some heat to it I suppose...... It won't be all that tight - it's just in a very awkward place. You may need to take the radiator out to get a good go at it.....

[katy]

Should the new switch have anti-seize grease?

NO, the grease may contaminate the brake fluid. If anything, use teflon tape, carefully, making sure that none gets past the end of the threads and into the fluid.