Brake Light Switch Failures

[svenedin]

At a car show last weekend there was a discussion about brake light switches and numerous failures. The modern switches are poorly made, arc inside and fail rapidly. Sometimes they continue to work but the brake lights only come on with hard braking.

One branch member told me his new brake light switch failed several times in a matter of weeks and another had a similar experience but his lasted a bit longer.

I was aware of this issue and when my old (original type) switch failed I fitted one of the new rubbish ones (because I didn't have time to find a NOS one) and fitted LED stop lights which drastically reduces the current going through the brake light switch. This worked fine but when I had my car re-painted the garage put incandescent stop lights back in and the switch failed about 2 weeks later!

One branch member had fitted a relay as per a Technical Tips article in Minor Matters. It seems easy to do. He has had no trouble since.

Has anybody else fitted and relay due to failing brake light switches or have LED lamps solved the problem instead?

I am not sure whether I am allowed to post the picture of the Minor Matters article on this.

Stephen

[59Elva]

Years ago I had a brake switch short out or get stuck on in a ‘61 Falcon. It got very hot and boiled the fluid in the junction block. The pedal went to the floor as I sailed thru a red light at the bottom of a hill, frantically down shifting and tugging at the hand brake. It stopped eventually and fortunately uneventfully.

[svenedin]

Years ago I had a brake switch short out or get stuck on in a ‘61 Falcon. It got very hot and boiled the fluid in the junction block. The pedal went to the floor as I sailed thru a red light at the bottom of a hill, frantically down shifting and tugging at the hand brake. It stopped eventually and fortunately uneventfully.

Wow! It had never occurred to me that could happen. I was only thinking about the switch failing and the brake lights not working. It is terrible what happened to you. Glad you survived!

I have to admit I have had my brakes fail too but not due to the switch. I was descending a long, steep hill aged 17 and having passed my driving test but still a novice really. I didn't change down and I just used the brakes to slow down. Towards the bottom of the hill where there was a sharp bend, the brakes did absolutely nothing. Somehow we went flying round the bend without coming off the road but I broke a leaf spring. A minute or two later and the brakes worked as if nothing had ever happened. My physics master, Mr Nigel Wood also had a Minor, a Traveller called Emu. I used to drive to school during my A-levels and I would park my Minor next to his. I told him about the brake incident and said I thought it was brake fade (drum expanding from heat and then the shoe not being able to move far enough for the friction material to make contact). My physics master said that sounds unlikely and set me the task of calculating whether brake fade was possible on this hill descent. It is quite an easy calculation. You have to know the height that was descended and so then one can assume that all of the gravitational potential energy that the car had at the top of the hill has been converted to heat in the brakes. Then the ratio of front brakes to back brakes 70:30, the coefficient of expansion of steel etc. Anyway, it was not brake fade from drum expansion. To get fade in this way would have needed a much, much bigger hill and our crude calculations did not take into account that the brakes are cooling as the car is driven and all the other loses of energy. What actually happened is the brake fluid boiled in the cylinders because it hadn't been changed for far too long. Water in the brake fluid lowers the boiling point of the fluid a lot. A serious lesson to pay attention to routine maintenance.

Stephen

[oliver90owner]

IMO, a limit switch on the brake pedal is a far better way to go. This was the first car I have owned which uses a pressure switch.

I hate the system on my EV which illuminates the brake lights while I am not aware of them. I would like some indication on the dash when they are illuminated.

[Sleeper]

Fitting a relay ( operated from the original switch ) is not a hard job, as is fitting a tell-tale lamp ( or LED ) on the dash...

John

[Bill_qaz]

Years ago I had a brake switch short out or get stuck on in a ‘61 Falcon. It got very hot and boiled the fluid in the junction block. The pedal went to the floor as I sailed thru a red light at the bottom of a hill, frantically down shifting and tugging at the hand brake. It stopped eventually and fortunately uneventfully.

Wow! It had never occurred to me that could happen. I was only thinking about the switch failing and the brake lights not working. It is terrible what happened to you. Glad you survived!

I have to admit I have had my brakes fail too but not due to the switch. I was descending a long, steep hill aged 17 and having passed my driving test but still a novice really. I didn't change down and I just used the brakes to slow down. Towards the bottom of the hill where there was a sharp bend, the brakes did absolutely nothing. Somehow we went flying round the bend without coming off the road but I broke a leaf spring. A minute or two later and the brakes worked as if nothing had ever happened. My physics master, Mr Nigel Wood also had a Minor, a Traveller called Emu. I used to drive to school during my A-levels and I would park my Minor next to his. I told him about the brake incident and said I thought it was brake fade (drum expanding from heat and then the shoe not being able to move far enough for the friction material to make contact). My physics master said that sounds unlikely and set me the task of calculating whether brake fade was possible on this hill descent. It is quite an easy calculation. You have to know the height that was descended and so then one can assume that all of the gravitational potential energy that the car had at the top of the hill has been converted to heat in the brakes. Then the ratio of front brakes to back brakes 70:30, the coefficient of expansion of steel etc. Anyway, it was not brake fade from drum expansion. To get fade in this way would have needed a much, much bigger hill and our crude calculations did not take into account that the brakes are cooling as the car is driven and all the other loses of energy. What actually happened is the brake fluid boiled in the cylinders because it hadn't been changed for far too long. Water in the brake fluid lowers the boiling point of the fluid a lot. A serious lesson to pay attention to routine maintenance.

Stephen

Stephen it's not drum expansion, it's the coefficient of friction of the lining material is drastically reduced once it exceeds a critical temperature. I have carried out brake fade tests on trucks were the actuation is by air, so no fluid to boil and brake fade can still be induced. Although if hydraulic actuation then fluid boiling point can be a contributing factor.

[svenedin]

Fitting a relay ( operated from the original switch ) is not a hard job, as is fitting a tell-tale lamp ( or LED ) on the dash...

John

I agree and I have just done exactly that except the tell-tale lamp.

I won't drill extra holes in my car so I mounted the relay on the bolt for the headlight wiring p-clip. The earth for the relay is to the headlight earthing point which is conveniently nearby. I made a little sub loom, correct wiring colours and bundled together with heat shrink. The wiring can be reverted to original in 2 minutes (the connections to the sub-loom are removed and the spade connectors fitted back to the brake switch directly.

It all works nicely and now there is an audible click from the relay when the brake lights come on. Doubt I'd hear it over the engine but can hear it with just the ignition on.

Would have been even neater with a relay socket but it wouldn't fit in the space where I wanted to mount it. For those happy to drill a new hole, a socket could easily be mounted. Then changing a relay is extremely simple. The fuse at 10 amps is too much and I will find a lower rated fuse.

Stephen

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[svenedin]

Years ago I had a brake switch short out or get stuck on in a ‘61 Falcon. It got very hot and boiled the fluid in the junction block. The pedal went to the floor as I sailed thru a red light at the bottom of a hill, frantically down shifting and tugging at the hand brake. It stopped eventually and fortunately uneventfully.

Wow! It had never occurred to me that could happen. I was only thinking about the switch failing and the brake lights not working. It is terrible what happened to you. Glad you survived!

I have to admit I have had my brakes fail too but not due to the switch. I was descending a long, steep hill aged 17 and having passed my driving test but still a novice really. I didn't change down and I just used the brakes to slow down. Towards the bottom of the hill where there was a sharp bend, the brakes did absolutely nothing. Somehow we went flying round the bend without coming off the road but I broke a leaf spring. A minute or two later and the brakes worked as if nothing had ever happened. My physics master, Mr Nigel Wood also had a Minor, a Traveller called Emu. I used to drive to school during my A-levels and I would park my Minor next to his. I told him about the brake incident and said I thought it was brake fade (drum expanding from heat and then the shoe not being able to move far enough for the friction material to make contact). My physics master said that sounds unlikely and set me the task of calculating whether brake fade was possible on this hill descent. It is quite an easy calculation. You have to know the height that was descended and so then one can assume that all of the gravitational potential energy that the car had at the top of the hill has been converted to heat in the brakes. Then the ratio of front brakes to back brakes 70:30, the coefficient of expansion of steel etc. Anyway, it was not brake fade from drum expansion. To get fade in this way would have needed a much, much bigger hill and our crude calculations did not take into account that the brakes are cooling as the car is driven and all the other loses of energy. What actually happened is the brake fluid boiled in the cylinders because it hadn't been changed for far too long. Water in the brake fluid lowers the boiling point of the fluid a lot. A serious lesson to pay attention to routine maintenance.

Stephen

Stephen it's not drum expansion, it's the coefficient of friction of the lining material is drastically reduced once it exceeds a critical temperature. I have carried out brake fade tests on trucks were the actuation is by air, so no fluid to boil and brake fade can still be induced. Although if hydraulic actuation then fluid boiling point can be a contributing factor.

Thanks for the explanation Bill. This may have been what happened because the brakes were fine so quickly afterwards but we will never know now. Suffice it to say, I quickly learned to use engine braking on long hills and to use the footbrake intermittently rather than constantly. We did have 4 rugby playing lads in the car, rather well oiled (but not me the driver of course). I'm sure that weight didn't help either.

Stephen

[svenedin]

The article on brake switch failures and fitting a relay or relay + LED lamps is in Minor Matters Jan/Feb 2019 Technical Tips page 45

I didn't pay any attention to it at the time because I had an original type switch fitted back then and it had not failed in many decades.

I do wonder whether the new type switches, which are heavily criticised as been poorly designed and not up to the job are simply not designed for use without a relay. Maybe they were never intended for the current of 3.5 Amps when using incandescent brake light bulbs.

Stephen

[King Kenny]

I think that there must have been a bad batch of switches. Several years ago I had two or three fail on me in quick succession. The one I have now has lasted for a few years so mabee they are better now. I had the same issue with flasher units failing after a short period too.

[svenedin]

I think that there must have been a bad batch of switches. Several years ago I had two or three fail on me in quick succession. The one I have now has lasted for a few years so mabee they are better now. I had the same issue with flasher units failing after a short period too.

That's reassuring to hear. I wonder whether they changed the internal design. I am told (by ESM) that the internals of the modern switches and originals are very different. They cut some open.

Stephen

[neilmorey]

I'll probably jinx it now but I read years ago that fitting a VW switch should be more reliable than the Lucas branded ones.
I fitted one of these probably around 10 years ago.
https://www.eurocarparts.com/p/fae-brak ... -464630010

[svenedin]

I'll probably jinx it now but I read years ago that fitting a VW switch should be more reliable than the Lucas branded ones.
I fitted one of these probably around 10 years ago.
https://www.eurocarparts.com/p/fae-brak ... -464630010

Yes the Minor Matters article mentions that better quality, more expensive switches should be more reliable but doesn't say what any of them are......

You're doing well with 10 years.

New old stock switches are probably the best bet in the absence of known good modern switches. I am sceptical because so many parts are the same old c**p made by the same factory but rebadged/rebranded and sold at many different prices.

Stephen

[Bill_qaz]

Hella make a lot of the VW electrical components. There switch is nearer to £20 but its spec still says 3 amp
HELLA 6DF 007 669-001

[svenedin]

Hella make a lot of the VW electrical components. There switch is nearer to £20 but its spec still says 3 amp
HELLA 6DF 007 669-001

Trouble is, Hella don't actually mention the amp rating at all on their own website!

https://shop.hella.com/hbvnlshop/hbvnl/ ... 0975826843

MGA Guru wrote a lot about poor quality brake light switches although the information is not up to date. The internal design of the bad ones are all the same and he shows pictures of the insides of switches. The old Lucas ones are much better made inside. He says that the bad switches are slow to make and break the circuit so they arc internally which destroys the contacts. The old Lucas ones would often fail with the brake lights on rather than the other way around. The internal design means that they close the circuit faster. My experience with two of the modern switches failing is that they stop responding or weakly respond to light pedal pressure and only close the circuit properly with firm pedal pressure. So there are no brake lights or dim brake lights for what I would call ordinary braking and only when the pedal is applied hard do the brake lights illuminate brightly. During several Minors on Tour "Le Drive" (a road trip) I have followed many Minors with dim brake lights. It is dangerous.

I do test my brake lights on my Minor but probably not as often as I should. if I drive in to my garage (rather than reverse in) I can close the door (which is black and remote controlled) and clearly see the brake lights working reflected on the door.

Stephen