No Brake Lights

[redmaestro]

I got home from my girlfriends late last night, and reversed into an empty parking space outside my house. I noticed that I couldn't see the brake lights in the reflection on the car behind me. I got out and checked all rear lights. Tail, fog, reverse and indicators are fine on both sides, just the brake lights not working. This afternoon I inspected both bulbs and the fuse (C5 - brake and reverse) and all were fine.

What else do I need to look out for? The haynes manual talks about some kind of switch by the pedal but I don't know what to look for?

As ever, thanks in advance!

Redm

[SimonR]

Hi there,

Yeah - there's a switch mounted above the brake pedal fulcrum that you could check. You need to get your hed right into the driver's side foot well to see it though - just follow the brake pedal upwards and you'll see it mounted. I wonder if you've got a wire adrift.

Hope that helps!

[redmaestro]

I've just located the brake switch and unbolted it. There are two spade connectors which are both firmly in place. I pressed the button on and off while a neighbour checked the lights and still nothing! :banghead:

Are there any more tests/checks I need to make?

[e692wtt]

I've just located the brake switch and unbolted it. There are two spade connectors which are both firmly in place. I pressed the button on and off while a neighbour checked the lights and still nothing! :banghead:


Did you have the ignition key at position '2' (the red 'battery not charging', orange 'low oil pressure' and red 'handbrake applied' lights should be showing on the dashboard at least) when you did this test?

[redmaestro]

Did you have the ignition key at position '2' (the red 'battery not charging', orange 'low oil pressure' and red 'handbrake applied' lights should be showing on the dashboard at least) when you did this test?

Hi E692,

Yes, I did have the ignition on '2' position. Also tried it with the engine running just in case but still no joy!

[e692wtt]

Call me Rich. OK, with the ignition key out of the barrel, try disconnecting the two spade connectors from the switch and then connecting them together with a bit of wire, then put the ignition to '2' (keep any exposed metal on the wire and connectors away from metal on the car or the fuse will go 'pop' which is fine but a bit inconvenient if you don't have a spare fuse).

Do the brake lights light up now?

[E_T_V]

As above join the two connectors together temporarily and see if that fixes it. If it does then you need a new switch (I've seen one in my garage somewhere recently). If not then I'd check the wiring to the boot in the hinge area for any frayed/chafed/broken wires.

[redmaestro]

Hi again,

Been busy testing the wiring - I bridged the two connectors with a 10amp fuse and still no lights. I checked the main fuse and even put the reverse lights on - still nothing.

The wiring in the hindge seems fine. I managed to peel the rubber gromet to expose most of the wiring loom and I couldn't see any signs of fraying. I also had a quick look at all the wiring looms behind the brake clusters to see if anything obvious, but still nothing!

[SimonR]

This seems like a stupid question but are you *sure* that both bulbs and bulb holders are OK?

Have you tested for +12V at the multiplug for the rear light clusters?

I only ask because I had the same thing on an old Daimler with the headlights - couldn't work out why both headlights had gone out at the same time and after removing and rebuilding the bulb fail modules it turned out that the mainbeam filaments had failed....

It would be sod's law, but the brake bulbs are dual-filament ones....

[redmaestro]

I connected my spare left side brake cluster with its own light bulbs to see if that would work but it didnt.

I havent tested anything with a multimeter because I don't know how to. I have zero knowledge on electrics, I wouldn't even know where to put the probes etc

[e692wtt]

I havent tested anything with a multimeter because I don't know how to. I have zero knowledge on electrics, I wouldn't even know where to put the probes etc

That actually helps us :) . Now we know this we can describe simple tests and not assume you understand the fine details of it all - or explain where and how to use a multimeter on your car to do some tests, which is dead simple and nothing to be scared of.

Have you got a multimeter?

[redmaestro]

Have you got a multimeter?

yes, well my dad has one :-)

[e692wtt]

OK, borrow your dad's multimeter and read the instructions - or get your dad to show you how to set it up to measure voltage - and get a 'feel' for it.

Then with the ignition key out try measuring the voltage between the car battery terminals using the instructions (or what your dad told you - ask your dad if you're not sure).

Then measure the voltage between the battery's positive terminal and the body of the car (again, ask your dad if you're not sure).

This will be a good starter exercise for you. :) , it doesn't get much more complicated than this, honest!

[SimonR]

OK, borrow your dad's multimeter ...

This will be a good starter exercise for you. :) , it doesn't get much more complicated than this, honest!

Indeed Rich - that's the long and the "short" of it. It really doesn't get any more difficult than that.

Once you've got a 12v (or anything from about 11.5v to 14v) reading on the multimeter by testing the battery, you can then get an assistant to press the brake pedal (with the ignition on position 2) and see if you get the same reading between the two terminals that contact the brake light bulbs. Then, if you're feeling confident, trace the back of the light cluster back to the multiplug and then you can test the multiplug terminals for voltage.

The only thing you have to be careful about when making measurements is that you don't accidentally touch both terminals with the same probe when working in confined spaces. It's usually no biggie if you do as in this kind of situation it'll just cause a bit of a spark and a blown fuse.

[redmaestro]

Just been looking at the car, still trying to solve the brake lights issue:

I tried the multi-meter test and couldn't get a reading (although 12v on the battery). I took the right-hand cluster off and got to the bulbs. I then turned ON all the lights (brake, lights, rev, fog and direction) and ALL bulbs lit up..... even the brake light. I asked my assistant to release the brake and that bulb was still lit up. I switched all the lights off, and all bulbs were OFF, tried the brake on its own and nothing!

Only the tail light will light up the brake bulb???:banghead:

[mgdavid]

sounds very much like an earthing problem, check the earth track on the light unit.

[redmaestro]

sounds very much like an earthing problem, check the earth track on the light unit.

How do I do that? I'm a complete novice :)

[SimonR]

I'll have a look tomorrow - just need to remove a rear light cluster so I can give you some info on where to look and what to test...

[G Force]

Only the tail light will light up the brake bulb???:banghead:

Hi redmaestro

I apologise if I am telling you something that you already know, but the brake light bulb has two filaments. A low wattage one that lights up when you turn on the tail lamp and a high wattage one that lights up when the brake is pressed.

It would be normal to have the bulb lit up with the lights on, unless you mean that the bulb was glowing bright as if the brake was pressed.

I realise you have tried a spare cluster and inspected the bulbs, but to rule out the remote chance of having 3 faulty bulbs why not fit two new stop & tail lamp bulbs for piece of mind?

[redmaestro]

...... I realise you have tried a spare cluster and inspected the bulbs, but to rule out the remote chance of having 3 faulty bulbs why not fit two new stop & tail lamp bulbs for piece of mind?

Hi GForce, I've just swapped the spare circuit boards over and still nothing. I guess the odds of 4 faulty bulbs are slim!

[G Force]

I guess the odds of 4 faulty bulbs are slim!

Yep Close to anorexic.:) I suppose its back to the multimeter testing then:(

[redmaestro]

Heh heh :-)

Now she is having a laugh! I've just noticed the tail/stop light comes on at 1 click of the ignition without head/sidelights or brake. Only one filiment will light up, regardless of whats on. This applies to both sides!!

[gharper]

Hi,

If you have a multimeter trace the route of the brake lite bulb back to the socket on the light cluster. put the red probe of the multimeter into the plug and the black probe onto the side of one of the holes where the bots for the cluster go through the body to see if there is voltage on the socket when you press the peddle. if there is not you can rule out the light cluster and probobally the earth. If there is then the light cluster is faulty.

The thing that springs out here is that BOTH lights are not working, so its not likely to be the clusters or wiring back to them. is there any voltage at the wire on the switch of the peddle? Again with this put the red probe on the switch wire spade and the black somewhere that has a good earth (or run a long wire from - side of the battery so you can use that as the earth to test) Try both of the wires to the switch. one of them should have voltage i beleive.

[e692wtt]

Try both of the wires to the switch. one of them should have voltage i beleive.

He tried that in Post 15, there is no voltage :confused: ?

Redmaestro, please clarify which filament in the stop/tail light is lighting up?

In fact, a clear description of which bulbs are lighting up at different times - or even a photo - would be very helpful, thanks :) .

gharper makes a good point, and I'd try what he says - this time, put the red probe to one of the connectors to the brake light switch and connect the black probe to the battery earth (which means you may need to extend it) with ignition at position '2'.

If you don't get 12v at one of the connectors to the brake light switch, try the other connector...

Let us know what you find.