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Brake light switch


JNC

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Have I got a underline problem ?  After last nights meeting when I got home the brake lights weren't working again ! . How long do the switches last ? When I take the switch apart there is burning to the connectors inside if I scrape them and spray contact cleaner they work again !, Do other members have the same problem ? . I'm going to try a different switch. Any thoughts welcome .

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It's a pretty common problem area, both not making properly and shorting on adjacent bits. Typical solutions include:

  1. Watching the actuation carefully and improving positioning and alignment.
  2. Taking apart and cleaning without the internal spring making a bid for freedom.
  3. Replacement, and I think that there's a better model suggested in the archives. Let us know if you can't find it. Edited: Crossed with Paul's.

Jonathan

 

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IMG_1742.jpg.2c4fa332cee41a8e3090e8e55940558b.jpg

IMG_2689.jpg.a88a6797fa60da73b93d47e7e16396d4.jpg

The new switch is shorter so I've put a swerve in the metal push bar !                                                                                                                                   (  Part No 51690 Intermotor  )

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  • 1 month later...

Mine recently failed - a matter of days after its MOT pass! 

It had an interesting - and fairly dangerous - failure mode. Worked fine when you test by tapping the pedal with a hand. Worked only intermittently when pressing smoothly and progressively with a foot (as you're supposed to do!).

Replaced with a new OEM unit from CC. Fine for the moment - we'll see how long that lasts!

If these parts are poor quality, why do CC persist in fitting them as OEM spec? Especially when the product as a whole, overall, is so good. Why don't they learn from the experiences of the community and make small inexpensive tweaks as a policy of continuous improvement?

It does smack a bit of spoiling the ship for a ha'porth of tar.

 

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Another solution which I once used on a Landrover is to use the brake light switch operate a relay which switches the brake lights.

The current that the brake light switch deals with will be reduced from around 4 Amps to 200 milliAmps.

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The problem used to be, and was with mine, the switch was trying to act as a pedal stop when the pedal came back up, bashing the plunger further through the contacts.

Mine failed within months of ownership, so dismantled, cleaned, reassembled and re-attached it to the car, paying attention to the operating bar and the switch, adjusting it so the switch wasn't being forced beyond it's movement.

That was 2001 - still working fine in 2017

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The original switch fitted to my car was fitted correctly, and didn't have any signs of arcing. However, when I disassembled it, it had ridiculously small contacts in a flimsy plastic casing. I would describe it as not fit for purpose, much like the plastic T piece that would have failed had I not changed it and the ungreased front bearings that I only checked after warnings here.......

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this was ironic. read this thread last night, thinking all true, but my switch has lasted quite a few years since it last failed. I do carry a spare.

MOT was today.

Brake light switch failed!!

talk about timing. swopped for new one from the boot, all sorted.

LED brake lights are my next thing.

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  • 3 years later...

The main issue with the brake light switch compared with most cars is that the full brake light current is directly passed through the contacts causing a major amount of arcing. I was getting a year or so on the first two switches on my car, I fitted a relay and have been on the same switch since 2015 now. Dropped the current from 4A down to 50mA with a relay in the pedal box, just needs a 'Y' pigtail for the input power, brake switch connected to the relay coil and ground, relay output to the brake lights.

Basically 4 pin relay with the following connections:

Pin 30 & 86 - 'Y' spaded pigtail lead with other end to existing 12V power supply that originally connected to the brake light switch.

Pin 85 - spaded lead from brake light switch.

Pin 30 - original spaded output to brake lights.

Flying lead from brake light switch to ground - spade on one end, ring terminal to nearby bolt on the other.

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I think every car I own and have owned runs full brake light current of around 3A (when running) through the pedal switch - although my Dodge might not as thats' full of complicated CAN-BUS stuff.

The contacts in the switch are more than capable of dealing with it - when set correctly - no over travel, and no dithering around the point of make/brake.

If your relay hasn't got something across the coil to deal with back EMF, you're back to arcing in the switch though with the high momentary voltage shoved back down the wire.

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The standard automotive relay used for a brake light relay is no different than the relay used to switch a higher current for headlight operation. Normal operating life for this type of relay is at least 100,000 cycles and relatively high impedance will significantly limit any current across the switch terminals due to any back EMF.

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You just don't need to over complicate it - set the switch so its not battered each time the pedal comes back to rest, the internal contacts are more than capable of handling the power put through them.  Take an automotive relay apart, and the internal contacts are smaller, but of course, set up to work properly.

I think on my commute, at 100,000 cycle lifetime, I'd need a new relay every week :)

 

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The standard Caterham supplied switch does not have any capability for rapid contact opening and closing with the simple copper plated bent metal contacts, no matter how it is adjusted. The contacts in the switch will arc with the default current flowing through 2x21W bulbs and an LED high mount stoplight. With a simple switch like that that is more akin to a door light switch, a relay is an east fix without replacing the switch itself, to solve the contact arcing problem.

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