Monkeybasher
|
| posted on 9/8/06 at 11:12 PM |
|
|
Brake light pressure switch
Hi,
I have a brake light pressure switch threaded into my master cylinder, the problem is I have to press the brakes very hard before the lights come
on . I have tried a new pressure switch but its still the same.
Any ideas
Thanks
Steve
|
|
|
|
|
MikeR
|
| posted on 9/8/06 at 11:30 PM |
|
|
is the switch above or below the pipe? ie - could there be air trapped between the switch and the fluid?
what are the numbers on the switch - i've been told you can get two pressures.
|
|
|
Monkeybasher
|
| posted on 9/8/06 at 11:46 PM |
|
|
Its above the pipe, I do have a bleed nipple on top of the master cylinder so wouldnt have thought air could be trapped, but its a good idea and as it
should be easy to swap I will try that tomorrow...eh I mean today, sh!t its late . I will check the number on it tomo..today too.
Cheers
Steve
|
|
|
chrisf
|
| posted on 10/8/06 at 01:07 AM |
|
|
My switch is mounted sideways and I too have to press the brakes quite a bit to get mine to light. I think on heavier cars, it causes no problem. But
on out lightweight cars, they stop too well for the switch.
--Chris
|
|
|
Danozeman
|
| posted on 10/8/06 at 06:02 AM |
|
|
MInes mounted sideways above the level of the m/cyl. The lights come on with only a slight press of the pedal.
Try bleeding it first.
Dan
Built the purple peril!! Let the modifications begin!!
http://www.eastangliankitcars.co.uk
|
|
|
NS Dev
|
| posted on 10/8/06 at 09:51 AM |
|
|
come on Mike!!!
bleeding it will make no "bleeding" difference as the pressure will be the same whether its air or fluid in there!!!
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
|
|
|
John Bonnett
|
| posted on 10/8/06 at 10:45 AM |
|
|
bleeding it will make no "bleeding" difference as the pressure will be the same whether its air or fluid in there!!!
Fluid is incompessible, air is compressible. If the pressure were the same with air and fluid brakes would not need bleeding. If the switch needs a
certain pressure to operate it I think entrapped air is a reasonable explanation as to why there is insufficient pressure.
I will of course be happy to be proved wrong.
John
|
|
|
Andy S
|
| posted on 10/8/06 at 10:59 AM |
|
|
Are you saying that the switch is measuring the pressure in the Master cylinder? - If so this may be the problem as the switch should measure the line
pressure which is some 10 times higher.
A good M/C pressure is about 1000PSI - Line pressure can be 10-20,000 PSI - The Brake switches are normally fitted in a small bore union in the line
to the front brakes or in a tee to the rears - this may also be why they have two pressures.
NSDEV is right - pressure is pressure air or fluid - one just takes less pedal distance to achieve as it does not compress - but the pressure is the
same only the volume is different.
Cheers
Andrew
|
|
|
watsonpj
|
| posted on 10/8/06 at 11:53 AM |
|
|
Do you have one master cylinder or 2 + bias bar. I had a similar problem as the rear brakes had so little pressure when adjusted to meet SVA that they
wouldn't turn the lights on till I was braking V.heavy. I added an additional switch on the front circuit and that fixed it.
|
|
|
MikeRJ
|
| posted on 10/8/06 at 03:27 PM |
|
|
quote:
Originally posted by John Bonnett
bleeding it will make no "bleeding" difference as the pressure will be the same whether its air or fluid in there!!!
Fluid is incompessible, air is compressible. If the pressure were the same with air and fluid brakes would not need bleeding.
You need to remove air from the braking system because the compressability of the air increases pedal travel (potentialy to the point where the brakes
exert virtualy no force) and reduces feel.
However, the air and fluid are both subject to the same pressure, a system can not magicaly have the air at one pressure and the fluid at another!
|
|
|
John Bonnett
|
| posted on 10/8/06 at 06:04 PM |
|
|
However, the air and fluid are both subject to the same pressure, a system can not magicaly have the air at one pressure and the fluid at another!
I have no argument with that. However, I do disagree that bleeding will make no difference. I think removing the air could solve the problem.
John
|
|
|
MikeR
|
| posted on 14/8/06 at 10:56 PM |
|
|
If its in the front of the system i'll agree with NS Dev, i'll agree with Nat. If its in the rear (and this is pre-sva) i'd say try
bleeding it. The rears do a lot less work, any air will reduce there effectiveness so you need to stamp on the brakes before it does anything.
Its my theory, i'm probably wrong but i'm sticking to it until i'm told it didn't make a difference.
|
|
|
irvined
|
| posted on 15/8/06 at 12:02 PM |
|
|
I have a similar thing on mine, its basically since i adjusted the rear bias a bucket load to make sure it got through SVA, i noticed i had to really
jump on the pedal to get the lights on.
Give the brakes a bleed just in case, if that doesnt cure it, try putting it on the front line.
HTH
David
http://irvined.blogspot.com
|
|
|
