Brake lights not working - nor brain! – Solved!!!
- Thread starter mrtask
- Start date
mrtask
Well-Known Member
Thanks for the mighty prompt and helpful reply, Richard. Touching the two wires together did indeed make the brake lights illuminate. Also produced sparks at the two touching wires. I can see the spade connectors are very green, so tomorrow I'll get the emery paper out and bring them back to copper colour again. Probably worth going through all the connections and doing the same, I suppose. If that doesn't fix the issue, the switch is dead, right?
The Rovering Member
Well-Known Member
Probably. Easy to change though, whip the old one out & have the new one in your hand to put it straight in so you don't let any air into the system.
The brake light switch is not difficult to change, but if at all possible use a hose clamp on the section between the master cylinder and the reservoir. By doing so you won't lose any fluid when the switch is removed nor will you allow air into the system.
vintage Girling Brake Hose Clamp 64947017 | eBay
Ron.
vintage Girling Brake Hose Clamp 64947017 | eBay
Ron.
The position of the switch can allow any debris in the system to collect above it and block the pressure, so it may be just needs a clean out. But if you take it out to clean it, you will have to stop the fluid leaking out and bleed it afterwards, so a bit of a pain. Best just to buy a new one of you can.
jp928
Well-Known Member
Some Porsche use brake light switches (dual circuit) UNDER the master cylinder , which makes them prone to failure caused by debris build up. Since either one working will turn on the brake lights this is not a huge problem. But when they fitted a system that detected only one firing and then lit a warning light on the dash (since it could indicate pressure loss in one circuit) it became very annoying. Fortunately the switches are cheap audi/VW parts.
cobraboy
Well-Known Member
You could test the switch before removing it, may save a lot of hassle. Wedge the brake pedal down hard with a piece of wood, or jack handle off the seat. Test for continuity with a multimeter across the (cleaned) switch terminals.
Bear in mind that if the switch needs replacing that switches come in two types, metric thread, and imperial thread, it is essential to get an imperial threaded switch. A metric threaded switch will screw in, but the thread is a sloppy fit and the switch may either leak or blow out with heavy emergency use. As the car is a single line system, total brake failure will result.
It would be preferable to keep a working OEM switch over a new Chinese one.
Bear in mind that if the switch needs replacing that switches come in two types, metric thread, and imperial thread, it is essential to get an imperial threaded switch. A metric threaded switch will screw in, but the thread is a sloppy fit and the switch may either leak or blow out with heavy emergency use. As the car is a single line system, total brake failure will result.
It would be preferable to keep a working OEM switch over a new Chinese one.
mrtask
Well-Known Member
Thanks for all the very helpful advice gentlemen.
Ron, thanks for that link, I promptly purchased that nice old hose clamp. I dare say it will come in handy again in the future. When it turns up I'll remove my switch (which I had been calling a 'sensor') and see if I can't clean it up and get it functioning again.
I seem to recall the last time a defunct brake switch needed to be replaced my mechanic mate just put a wet rag underneath, and swapped the new for the old very quickly, so as not to let any air into the system. We didn't need to bleed it afterwards. He did however make the mistake Cobraboy warned about, and fitted one with a metric thread at first. I drove all the way from Berlin to Austria and back (!) before I realised I was losing brake fluid, and traced the leak to the new switch. We then installed one with the correct thread, but the paint beneath the switch and down the one side of the front crossmember had sustained some damage from the leaked fluid. Still, nobody is looking down there, and I eventually repainted it when I subsequently pulled the motor to install a manual gearbox.
I'll report back when i get this issue dealt with.
Ron, thanks for that link, I promptly purchased that nice old hose clamp. I dare say it will come in handy again in the future. When it turns up I'll remove my switch (which I had been calling a 'sensor') and see if I can't clean it up and get it functioning again.
I seem to recall the last time a defunct brake switch needed to be replaced my mechanic mate just put a wet rag underneath, and swapped the new for the old very quickly, so as not to let any air into the system. We didn't need to bleed it afterwards. He did however make the mistake Cobraboy warned about, and fitted one with a metric thread at first. I drove all the way from Berlin to Austria and back (!) before I realised I was losing brake fluid, and traced the leak to the new switch. We then installed one with the correct thread, but the paint beneath the switch and down the one side of the front crossmember had sustained some damage from the leaked fluid. Still, nobody is looking down there, and I eventually repainted it when I subsequently pulled the motor to install a manual gearbox.
I'll report back when i get this issue dealt with.
cobraboy
Well-Known Member
So, the switch is dead. You cleaned the terminals, put pressure on the hydraulics, and there was no continuity across the terminals with a meter.
OK, Now if that were me faced with a dead switch I would harvest one from an old BL car from period, yes seriously ! Who knows where the modern stuff is made ? I can tell you it is not in Wales, as the QH factory closed in 2013.
Repro stuff is usually crap, already Demetris has confirmed this statement above.
Shiny is not always better !
OK, Now if that were me faced with a dead switch I would harvest one from an old BL car from period, yes seriously ! Who knows where the modern stuff is made ? I can tell you it is not in Wales, as the QH factory closed in 2013.
Repro stuff is usually crap, already Demetris has confirmed this statement above.
Shiny is not always better !
mrtask
Well-Known Member
@cobraboy Ding Dong!
Nope, I must admit, I haven't yet carry out the procedure you helpfully outlined above. Blush. For want of a multimeter. I plan to borrow one tomorrow or at the wknd. With a bit of luck my mate will be able to show me how to measure continuity with his multimeter. I confess complete ignorance of these things. I can change a light bulb, but not much more when it comes to electrickery.
Failing that I'll invest in my own multimeter, as it's probably about time I obtained my own. Anybody reading this have any suggestions regarding which to buy, for the not very ambitious amateur?
I haven't the faintest idea how or where to 'harvest' anything from an old BL car, or any other kind of old car for that matter, there not being any junkyards left in these parts. I am reliant on the interwebs, alas. I suppose I could post a wanted ad on here, and maybe ask on farcebook in the P6 Club pages?
Hmm, so if the UK QH factory closed nearly a decade ago, does that mean the QH branded water pump I had fitted two years ago also came from the far east? Crikey, I expect that'll be the next component to fail then.
Nope, I must admit, I haven't yet carry out the procedure you helpfully outlined above. Blush. For want of a multimeter. I plan to borrow one tomorrow or at the wknd. With a bit of luck my mate will be able to show me how to measure continuity with his multimeter. I confess complete ignorance of these things. I can change a light bulb, but not much more when it comes to electrickery.
Failing that I'll invest in my own multimeter, as it's probably about time I obtained my own. Anybody reading this have any suggestions regarding which to buy, for the not very ambitious amateur?
I haven't the faintest idea how or where to 'harvest' anything from an old BL car, or any other kind of old car for that matter, there not being any junkyards left in these parts. I am reliant on the interwebs, alas. I suppose I could post a wanted ad on here, and maybe ask on farcebook in the P6 Club pages?
Hmm, so if the UK QH factory closed nearly a decade ago, does that mean the QH branded water pump I had fitted two years ago also came from the far east? Crikey, I expect that'll be the next component to fail then.
cobraboy
Well-Known Member
Here ya go
I had the Draper one for years and years, they all come with distructions, you simply set the dial to continuity, or 12v if testing a circuit etc, and off you go !
Top 10: Best Multimeters
You should have one, it's fun ! and it will save you a fortune in garage bills.
Until your new meter arrives just scrub up the terminals on the brake switch with a small file, plug the wires back on, squeezing with pliers to make them nice and tight, and I bet you'll have brake lights.
I know, you don't have a small file, well your wife has a nice diamond grit nail file in her handbag, just the jobbie, best not get caught eh........
PS
We have several donor Jags at work, I could look for a switch if you are really stuck.
I had the Draper one for years and years, they all come with distructions, you simply set the dial to continuity, or 12v if testing a circuit etc, and off you go !
Top 10: Best Multimeters
You should have one, it's fun ! and it will save you a fortune in garage bills.
Until your new meter arrives just scrub up the terminals on the brake switch with a small file, plug the wires back on, squeezing with pliers to make them nice and tight, and I bet you'll have brake lights.
I know, you don't have a small file, well your wife has a nice diamond grit nail file in her handbag, just the jobbie, best not get caught eh........
PS
We have several donor Jags at work, I could look for a switch if you are really stuck.
My pleasure Alisdair. I have never managed to reuse a brake light switch that had failed, but you will hopefully have more luck. If you can acquire a NOS item, even second-hand, that will be infinitely better than the modern alternative. Some years ago the Lucas item failed and I fitted a non-genuine replacement. It went on and came off the very same day. The only way the lights would come on was when I stood on the brake pedal, ridiculous. Fitted a genuine second-hand item and that kept me out of trouble for a time. There is a brass washer beneath the switch that you must use, as that will prevent leaks from occurring.
You might be lucky with your QH water pump, hopefully, it was made in Wales. My Rover is running a QH pump, the best pump bar none I have ever used. Fitted in 2008, still running perfectly with 200,000 miles (322,000km) on it!
Ron.
mrtask
Well-Known Member
Update.
So I decided to just get a new switch, fit it myself, and enjoy driving with working brake lights a.s.a.p! I bought a QH switch like in the link I posted above, it arrived promptly the next day, and armed with my new hose clamp tool I got to work! Gung ho, and confident of my wrenching abilities!
As instructed per this thread, I clamped off the fluid reservoir-to-master cylinder flexible hose, so as not to lose any fluid or allow air into the hydraulic system. I removed the old defunct brake switch and promptly put the new part in, carefully, at first just by hand. Except it simply wouldn’t completely tighten up. At that last turn of the wrench, it felt as if it kept ‘cross threading’. Sure enough, although the brake pedal still felt firm, one push on the pedal and it went straight to the floor, squirting out brake fluid from right where the new switch was fitted. Damn and blast!
So after clearing that up promptly, I swapped over the brass washer again and re-fitted the original albeit defunct switch, and got it tightened up securely, with no fluid leakage. Thankfully I can still drive my car while I try and resolve this issue, although the brake lights still don’t work, obviously.
After that, I closely examined the replacement switch, and, well, I don't know. It looks to me as if there is a defect on the thread, one thread wind down from the tip. Manufacturing fault, or me having been "cack handed"? Whatever, it's dud, it won't seal safely.
Here's the weird thing; there were some remnants of what I suppose was PTFE tape on the thread of the dud switch when I took it out. If some of it stayed in the union, would that really have been able to mash up the thread on the switch!?!? I can't believe Chinesium is so soft that PTFE tape could deform it.
Unfortunately it is very difficult to see in a photograph, although I'm attaching one anyway. What do you guys reckon? Could this be a faulty part, or is it more likely I managed to damage the thread myself?
So I decided to just get a new switch, fit it myself, and enjoy driving with working brake lights a.s.a.p! I bought a QH switch like in the link I posted above, it arrived promptly the next day, and armed with my new hose clamp tool I got to work! Gung ho, and confident of my wrenching abilities!
As instructed per this thread, I clamped off the fluid reservoir-to-master cylinder flexible hose, so as not to lose any fluid or allow air into the hydraulic system. I removed the old defunct brake switch and promptly put the new part in, carefully, at first just by hand. Except it simply wouldn’t completely tighten up. At that last turn of the wrench, it felt as if it kept ‘cross threading’. Sure enough, although the brake pedal still felt firm, one push on the pedal and it went straight to the floor, squirting out brake fluid from right where the new switch was fitted. Damn and blast!
So after clearing that up promptly, I swapped over the brass washer again and re-fitted the original albeit defunct switch, and got it tightened up securely, with no fluid leakage. Thankfully I can still drive my car while I try and resolve this issue, although the brake lights still don’t work, obviously.
After that, I closely examined the replacement switch, and, well, I don't know. It looks to me as if there is a defect on the thread, one thread wind down from the tip. Manufacturing fault, or me having been "cack handed"? Whatever, it's dud, it won't seal safely.
Here's the weird thing; there were some remnants of what I suppose was PTFE tape on the thread of the dud switch when I took it out. If some of it stayed in the union, would that really have been able to mash up the thread on the switch!?!? I can't believe Chinesium is so soft that PTFE tape could deform it.
Unfortunately it is very difficult to see in a photograph, although I'm attaching one anyway. What do you guys reckon? Could this be a faulty part, or is it more likely I managed to damage the thread myself?
What a pain
For what it is worth, I tend to think the thread was damaged before you fitted it. In any case, the switch does not form a seal with the threads, rather it is formed at the tip. The reason for not sealing would be the shape and dimensions of the tip. If you can, remove the old switch and closely compare their tips. Mind you, it may not be obvious, but there is something there that is different.
Ron.
For what it is worth, I tend to think the thread was damaged before you fitted it. In any case, the switch does not form a seal with the threads, rather it is formed at the tip. The reason for not sealing would be the shape and dimensions of the tip. If you can, remove the old switch and closely compare their tips. Mind you, it may not be obvious, but there is something there that is different.
Ron.