Brake warning light on

witorque · Post by **witorque** » Sun Jul 15, 12 3:19 pm

I have lived with the brake warning light being on ever since I have had my 72 Challenger. It goes off if the wire is un plugged on the actuator valve on the inner wing.
I tried bleeding the front then the rear, as this is how I used to do it on a Triumph Stag, but no joy with the Challenger....
Is there a different method on a Mopar?
Could something stick in the valve?

Adrian Worman · Post by **Adrian Worman** » Sun Jul 15, 12 3:21 pm

Faulty switch at the valve, easy to strip and inspect for crud and corrosion tho

witorque · Post by **witorque** » Sun Jul 15, 12 3:31 pm

Is the switch removable without the messy job of taking the whole unit off and having to bleed the brakes again?
Do service kits / seal kits exist?
I see year One list a new one for $125

Cannonball · Post by **Cannonball** » Sun Jul 15, 12 4:37 pm

Adrian Worman wrote:Faulty switch at the valve, easy to strip and inspect for crud and corrosion tho

het ade
what was dragstalgia like.......

witorque · Post by **witorque** » Sun Jul 15, 12 5:21 pm

Removed the switch which works, but I guess the internal shuttle is stuck.
Looks like it is best removed to do that.....
What does the little plunger on top do?

JohnR · Post by **JohnR** » Sun Jul 15, 12 8:03 pm

Makes contact with the bit inside to switch the light on , I think you can move it to and fro from the outside , might be gummed up with crud ,or just rusty !!!

witorque · Post by **witorque** » Sun Jul 15, 12 9:50 pm

Are there any seals inside? If I take it appart and can't replace unobtainable seals (other than O rings) I may as well replace it?

Steve · Post by **Steve** » Sun Jul 15, 12 10:52 pm

If you need custom seals there is a company near me called Roger Tims Seals. If they havent got what you need then no one will! If you need to, more than welcome to post them to me when stripped and I will take them in for you, get what you want and post back.

Cheers Steve

witorque · Post by **witorque** » Mon Jul 16, 12 7:50 am

I think I'd best not tamper with it until after the Nats
Thanks for the tips guys

Dave999 · Post by **Dave999** » Mon Jul 16, 12 8:18 am

2 minute job

you could do it wearing a white suit and flip flops

Brake warning light consists of a piston a spring and 2 metal contacts

if the piston is touching either contact the light is on

the piston will only move to touch one of the contacts if the pressure in the front or rear circuit is not balanced....i.e over zealouse bleeding of the brakes or a failure of a line, cylinder or caliper

to reset

find the only port on the master cylinder or in older cars on the distribution block mounted to inner wing or bulkhead that has a wire going to it and 3 brake pipes

pull off the wire and put on a ring spanner

you undo the collar on the switch by 4-8 mm and you will hear the piston spring back TOCK

no need to bleed or get covered in brake fluid

the spring is strong

do up the collar again and try the brakes

only other thing that makes this light come in is use of the hand brake

the switch is on the back of the handbrake housing under the carpet

Dave

witorque · Post by **witorque** » Mon Jul 16, 12 9:18 am

When the wire is disconnected, the light goes off
I removed the electric switch and plunged it by hand, the light goes on & off
No sign of the internal shuttle going back with a 'Tock' when the switch is removed.....
It looks like the second photo in -grey one shown here
http://inlinetube.com/Prop%20Valves/pro_valves.htm

Dave999 · Post by **Dave999** » Tue Jul 17, 12 9:07 am

tres odd

mind your car is 2-3 years newer.....

i could be wrong but i was under the impression that regardles of the distribution block or master-cylinder they all worked the same way

wonder if the spring is missing

or its completely different

now you have plunged it in and out a bit

try standing on the brakes to see if it centralises and the light goes out

Adrian Worman · Post by **Adrian Worman** » Tue Jul 17, 12 10:39 am

The one on my 72 is identical Chris, I remember servicing it when I installed the m/cyl but that was probably 15 yrs ago

Dave-R · Post by **Dave-R** » Tue Jul 17, 12 10:49 am

Might help?

Dave-R · Post by **Dave-R** » Tue Jul 17, 12 10:59 am

witorque wrote:When the wire is disconnected, the light goes off
I removed the electric switch and plunged it by hand, the light goes on & off
No sign of the internal shuttle going back with a 'Tock' when the switch is removed.....
It looks like the second photo in -grey one shown here
http://inlinetube.com/Prop%20Valves/pro_valves.htm

You can see by the diagrams I posted that the switch works by grounding against a piston in the middle. If the light is coming on then the switch is shorting against the piston or the body of the switch.

The switch is adjustable for depth. If the threaded bit is screwed in too much it will contact the piston under it and make the light go on.

So I suggest you think about how it works by looking at the diagrams and then you should be able to suss out how the switch is grounding itself.

It does all come apart if you need to clean it out.

I don't see how the switch works if you remove it and plunge it by hand. How is it finding a ground to the battery -ve?