wombat
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| posted on 23/5/13 at 06:44 AM |
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Handbrake / brake test / twin res - help please
Morning folks, having got nearly all of the loom sorted I am stuck with the brake test illumination and switching, so if you could spare a moment I
would appreciate it :-
I have the following set up:-
Twin master cylinders (OBP )with fluid sensors fitted into the caps
Standard Sierra handbrake with switch
Warning light for dash
Test switch (not purchased yet - what have you used?)
Am I correct that I just need to t- off the black/white handbrake wire and use this T to link reservoirs to test switch then to its original spade on
the warning light?
Confused.wom
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big_wasa
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| posted on 23/5/13 at 07:49 AM |
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You don't need a test switch you can just pull the handbrake to test it.
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wombat
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| posted on 23/5/13 at 08:45 AM |
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Really ?
I understood from various searches that there has to be a test other than the handbrake?
Like a push button on top of the master cylinder for example............
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loggyboy
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| posted on 23/5/13 at 09:38 AM |
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quote:
Originally posted by wombat
Really ?
I understood from various searches that there has to be a test other than the handbrake?
Like a push button on top of the master cylinder for example............
The test switch needs to be from the drivers seat.
The idea behind the warning light is that it will act as a low fluid warning AND a failure warning. (there are two IVA RS's to meet - one for
low fluid, the other for brake failure/pressure loss). You can meet the first RS by having your fluid level visable through the side of the MC
reservoir, but you will still need either a hydraulic pressure sensor (expensive) or a fluid level sensor to show any possible failure in the
system).
The test switch CAN be the handbrake (as long as its connected to a switch) as the hand brake warning light can be combined with the low fluid light
as a 'general' brake warning light. Theres nothing to stop you having both.
The test switch is not to test that there is fluid, its to test the warning light bulb hasnt blown.
[Edited on 23-5-13 by loggyboy]
Mistral Motorsport
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wombat
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| posted on 23/5/13 at 10:01 AM |
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Thx Loggy, thought you might respond too, nearly contacted you direct instead of posting !
So:-
1. I mis-understood the switch part, didnt realise the handbrake could be THE switch (duh.....)
2. But I will need an hydraulic switch for my foot brake still
3. As OP - If I break into the B/W from the hanbrake wire going to the warning light, and link the resevoirs in series, this should do the trick?
Amazing that I have built it all so far without any form of manual (lots of help from LCB to be fair), but cant get my head around this.............
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matt_gsxr
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| posted on 23/5/13 at 10:18 AM |
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You will need to have the handbrake switch, Reservoir 1 switch and Reservoir 2 switch all IN PARALLEL.
Any one of them must switch the warning light on.
If you have them all in series, then you would have to have run out of brake fluid in both reservoirs and have your handbrake on for it to light!!!!
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loggyboy
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| posted on 23/5/13 at 10:20 AM |
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quote:
Originally posted by wombat
Thx Loggy, thought you might respond too, nearly contacted you direct instead of posting !
So:-
1. I mis-understood the switch part, didnt realise the handbrake could be THE switch (duh.....)
2. But I will need an hydraulic switch for my foot brake still
3. As OP - If I break into the B/W from the hanbrake wire going to the warning light, and link the resevoirs in series, this should do the trick?
Amazing that I have built it all so far without any form of manual (lots of help from LCB to be fair), but cant get my head around this.............
You will need something to make the brake lights come on, this can either my a hydraulic brake switch which is connected to the brake lines via
T-peice. (there have been some who have found these unreliable and prone to being air traps) the alternative is a mechanical switch connected to the
brake pedal, which is the common OE way of doing things. (usually these are push to break, not push to make)
You dont want to break the cable from the fluid level sensor warning light, the test switch needs to be in parallel, other wise it will only work when
both the hand brake switch is used AND the fluid is low, you want it to be OR.
Worth having a run through the manual, theres alot there but 90% of it is not relevant to our cars or fairly obvious, its just a matter of reading it
3 or 4 times to get the gist of what they want.
Mistral Motorsport
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loggyboy
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| posted on 23/5/13 at 12:08 PM |
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Basic diagram of how you could wire it, im sure there other ways but this is the most straight forward IMO
 
Brake Warning Wiring
[Edited on 23-5-13 by loggyboy]
Mistral Motorsport
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wombat
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| posted on 23/5/13 at 06:00 PM |
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Thx for the drawing Loggy but I am still confused....
Handbrake switch is one cable b/w which I believe to be "switched to earth"
Warning Light - has b/w wire - assume this goes directly to above
2x green wires(joined)- I believe this is supply - this according to diagrams is supply to various warning lights
Aaaaargh .............
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snowy2
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| posted on 26/5/13 at 06:05 AM |
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i have used hydraulic brake switches on every kit i have built (now at 10 cars.... no kids :-( ) and replaced the pedal switch on those part built
cars i buy when they went faulty, i have never had a problem with the hydraulic switches. i hear folks have problems but its always a mate of a friend
says they have a problem, never a first hand account.
i would say they are reliable and easy to fit. on a restricted pedal box the mechanical switches can be a royal pain to set up in an area where they
wont get constantly kicked and dislodged...they (the two basic types of brake switch) each have their merits.
sometimes you are the pigeon, most of the time the statue.
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snowy2
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| posted on 26/5/13 at 06:37 AM |
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the green wire will supply various lights, in exactly the same way as your battery supplies all circuits but the battery should have ideally one
connection to it not dozens......
the supply for the brake switch can come from ANY suitable ignition supplied source, a single wire can supply the master cyls and the hand brake
sw.
the simplest method is take a live wire from the ignition switched source of choice and connect it to the bulb. then connect TWO wires to the other
side of the bulb, one goes to the master cyls (one terminal only then linked to the other master cyl) the other wire from the bulb goes to the hand
brake switch. the master cyls need BOTH to be earthed.....
Thus when the hand brake is on the light illuminates OR if either master cyl is low the bulb will illuminate
sometimes you are the pigeon, most of the time the statue.
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