Oh c**k!
speedyxjs - 27/12/09 at 12:45 PM
So much for finishing the wiring today, iv fried the electrics 
I was wiring the brake warning using a relay (due to this).
I unscrewed the cap to make sure the light came on, it did but when i put the cap back on, the light didnt go out. If i unplugged the relay and put it
back in again, the light was off so i decided the problem must be that i needed something connected to the 5th pin so (stupidly) i connected it
straight to ground.
Switched the ignition on and have fried all the ignition wires
Im off to look for a new steering column
Any idea's why it has fried?
[Edited on 27-12-09 by speedyxjs]
speedyxjs - 27/12/09 at 01:07 PM
This is how i have wired the relay:
meany - 27/12/09 at 06:42 PM
this maybe of help.
scroll down to "The Famous Bosch Relay".
http://www.bcae1.com/relays.htm
dinosaurjuice - 27/12/09 at 07:40 PM
quote:
Originally posted by speedyxjs
Any idea's why it has fried?
[Edited on 27-12-09 by speedyxjs]
was it fused?
Dave Bailey - 27/12/09 at 10:19 PM
Sorry but I thought that the brake warning lights illuminte by switching to gnd... either through:-
Hand Brake switch
Brake Fluid switch
Test Switch.
These should all normally open...
Is this not how things work? All should be fused to protect the wiring.....
Dave B
SteveWalker - 27/12/09 at 11:53 PM
Dave's right. The handbrake light is fed from the switched live from the ignition switch, via a fuse, to the bulb and the negative side of the
bulb is grounded by the handbrake/fluid level/test switches when they operate.
iank - 28/12/09 at 04:41 PM
I agree with Dave and Steve. Flak posted a diagram on the other thread about how it is normally wired. I've never seen a relay be required, and
it's not ideal as these things are designed to fail safe and a relay adds a failure mode.
Maybe this diagram will help.
Description
David Jenkins - 28/12/09 at 04:50 PM
^^^^^^
That's how mine is wired... except the 'test switch' is attached to my handbrake. Handbrake on, or low fluid, lights the lamp.
iank - 28/12/09 at 05:08 PM
quote:
Originally posted by David Jenkins
^^^^^^
That's how mine is wired... except the 'test switch' is attached to my handbrake. Handbrake on, or low fluid, lights the lamp.
The handbrake switch is the legally required warning light bulb test switch (and has the good point of being automatic* since 'ordinary'
punters don't remember to press the test switch). Its secondary function (not required legally) is to indicate you may have forgotten to take
the handbrake off for people who can't tell why they are going more slowly than usual and there's a strange smell coming from the back of
the car 
* it also has one very bad point, Consider how many people not seeing the brake fail warning at ignition time would ignore the blown bulb as
'it's just a handbrake reminder!'
twinturbo - 28/12/09 at 05:39 PM
Since when was it a legal requirement to have a brake warning light?
TT
flak monkey - 28/12/09 at 05:40 PM
quote:
Originally posted by twinturbo
Since when was it a legal requirement to have a brake warning light?
TT
Since about 1970, possibly earlier.
twinturbo - 28/12/09 at 05:45 PM
That's strange as many production cars at least up to the mid 80's had no fluid warning, and some had not even progressed to the handbrake
warning light.
TT
David Jenkins - 28/12/09 at 05:52 PM
Not sure that I agree with Ian's "legal requirement" bit - but a switch attached to the handbrake is a quick and easy way to meet the
IVA requirement for a way to test the "low brake fluid level" circuit & lamp.
If you're driving along and the light comes on - check the handbrake. If that's off, then pull over 'cos you're running out of
brake fluid!
boggle - 28/12/09 at 06:19 PM
early landrover defenders had no handbrake warning light......
flak monkey - 28/12/09 at 06:25 PM
Fair enough. It was a guess. The mk1 escort loom I had had a dash mounted test switch.
iank - 28/12/09 at 06:36 PM
quote:
Originally posted by twinturbo
That's strange as many production cars at least up to the mid 80's had no fluid warning, and some had not even progressed to the handbrake
warning light.
TT
That "handbrake warning light" is actually the low fluid light! Which plays to my point about people not knowing what that light actually
means.
iank - 28/12/09 at 06:53 PM
I'm struggling to find the original legal requirements in the construction and use regulations as HM Govt only puts acts post 1987 on their
website.
Needless to say both the SVA and IVA regulations are clear on the requirement for a brake fluid warning lamp with a test switch of some kind (can be
via the ignition switch and a timer, a switch on the dash or a handbrake switch), and have no requirement for a handbrake warning lamp.
twinturbo - 28/12/09 at 07:32 PM
Strange..
Anyway, as seems to be the case with lots of things it's not covered under the MOT.
TT
speedyxjs - 28/12/09 at 09:53 PM
Cheers for the replys guys. No it wasnt fused so that would explain it.
Im not using a sierra master cylinder which is why mine works differently.
iank - 29/12/09 at 01:05 AM
quote:
Originally posted by speedyxjs
Cheers for the replys guys. No it wasnt fused so that would explain it.
Im not using a sierra master cylinder which is why mine works differently.
Yeah, we are aware it's a Jag item, but afaik all manufacturers use the same method as it's the most simple. They don't tend to go
around requiring relays as that's a couple of quid off their profit margin and a another thing to go wrong at some point.
Do you have a wiring diagram for the MC or the Jag it came from?
02GF74 - 29/12/09 at 03:49 PM
quote:
Originally posted by speedyxjs
I unscrewed the cap to make sure the light came on, it did but when i put the cap back on, the light didnt go out. If i unplugged the relay and put it
back in again, the light was off so i decided the problem must be that i needed something connected to the 5th pin so (stupidly) i connected it
straight to ground.
Switched the ignition on and have fried all the ignition wires
dude, never do stuff like that i.e. connect wires ad hoc.
there are a number of peeps that have good understanding of electrics that will provide advice so a little bit of patience would have saved a lot of
hassle.
