20 replies to this topic

[yorkshirechris]

Might be a silly question but...

At the moment, the tester for the brake fluid level consists of two wires entering a multiplug which plugs into the side/front of the master cylinder (I think) rather than the type that has two spade terminals going onto tags on the fluid filler cap.

Being that I'm having a problems with the brake fluid test switch (which I need to investigate) and the two wires are just soldered into the multi plug I'm going to replace the plug anyway...

Basically, can I replace this plug thingy with this, and stick a couple of spade terminals on the two wires?

Also while I'm here can anyone advise me on what else to check on this circuit... the bulb will not light when I press the switch. I've changed the switch and the bulb inside the current switch looks fine. Where does it take it's live from?

Am I right in saying there should be an earth, a live connected to the bottom of the switch (which makes a connection when the switch is pressed) and a live connected to the top of the switch but which is broken by the brake fluid filler cap?

Cheers!

Edited by yorkshirechris, 10 April 2009 - 07:55 PM.

[taffy1967]

If you own a post October 1988 Mini (one fitted with a tandem brake servo), then I'd say that is the correct type of cap to use and yes using a pair of spade terminals on the end of the wires will be fine. That's how mine is connected anyway as the original spade terminals rotted away years ago.

Anyway, are you sure the dash switch block unit itself has the 2 spade terminals connected on both sides (in addition to it being connected to the multi-plug)? These are required if the bulb is to light up.

Plus the bulb could just be dead and it's easy to remove by using the round end of a spade connector and gently squeezing as you turn it anti-clockwise?

Edited by taffy1967, 10 April 2009 - 09:28 PM.

[Disco Dan]

Heres a wiring diagram:

(Taken from FAQ)

[yorkshirechris]

Without looking I'm pretty sure it did have two spades, one going to each side.

It's a 1980 mini GT so do you think the cap will be okay to use? I dont know what sort of braking system it is or whatever, not really my forté (well not much on the Mini is to be honest )

[Ethel]

Yours is an earlier master cylinder with an actual pressure failure warning switch. I don't think a later cap would fit and even if it did the float would reduce the capacity of the reservoir which isn't a good idea.

[yorkshirechris]

Yours is an earlier master cylinder with an actual pressure failure warning switch. I don't think a later cap would fit and even if it did the float would reduce the capacity of the reservoir which isn't a good idea.

Hmm. I best try cancel my order from minispares then

I think I'm just going to have to tinker around with it. If it turns out that the bulb lights up when I short the two wires going to the master cylinder, thus proving the fault into whatever these two wires go into, then what?

[Ethel]

Assuming the seals in the cylinder are ok you should be able to unscrew the switch from the cylinder. To test it you could put a continuity tester across the terminals, slacken off a bleed nipple & push the pedal to simulate a pressure failure.

The switch not lighting the bulb has nothing to do with the switch on the cylinder though, There should be a live going directly to the bulb that can be earthed by either the test switch or the cylinder switch.

[yorkshirechris]

The switch not lighting the bulb has nothing to do with the switch on the cylinder though, There should be a live going directly to the bulb that can be earthed by either the test switch or the cylinder switch.

Mmm good point. When I get a minute (been busy in the sunshine today ) I'll have to investigate it properly starting from the dashboard switch.

About the wiring diagram above... I've looked at it a few times and am still confused... I can see what colour each wire should be, but what conditions (i.e. voltage) should I be seeing on each of the wires:

Black/White
Black/White spade terminal?
Violet

I know that the black is earth and I'll need to check that against a good earth.

Cheers

[yorkshirechris]

Anyone?

I'm just after an idea of which wires trace back to where. I take it Violet is a direct power feed, does one of the black/whites go directly to one side of the master cylinder switch and the other side of the switch is a live? If so where does the second black/white go?

[robtheplod]

sorry to jump onto this thread, but I have a similar problem in that I have no wires going to the filler cap at all even though I have spade terminals on it - no loose wires about anywhere. I've got a 1996 mini - where do the wires come from that are supposed to be connected to the cap??
thanks!

[yorkshirechris]

Right then boys and girls, the plot thickens...

Went at it with a multimeter today and threw all my skills at it... All of the following tests were done with the ignition off & key out, but with the battery etc all still connected...

Let's start at the switch. I'm getting 12V on the Violet wire. I'm getting an excellent earth on the two Black wires which go into the middle terminal of the multiplug. I'm getting nothing (no earth/voltage) on either of the black/white wires.

I've utilised a spare sidelight bulb and tested the positive & earth and it lights, proving the positive & earth going to the switch are ok. I have two switches, I've dismantled both of them and the bulbs in both switches look absolutely fine - but neither of the bulbs light when the switch is pressed. I've even tried running a temporary new earth to the switch and that makes no difference.

Silly question, but have I proved this fault onto the bulbs? It seems weird that two bulbs would be knackered though, being that both of them look fine?

Now onto the second part...

I'm getting no voltage or earth conditions on either of the two black/whites which go into the master cylinder. Should I be?

Please help!!

[yorkshirechris]

Anyone?

[Disco Dan]

Wire diagrams for later fuel injection models...

[yorkshirechris]

That helps, do you know if this is applicable to a 1980 GT? It certainly looks how mine is wired.

Judging by that diagram and going by what I said above, it looks like I need a new switch (or bulb to put in the switch - are these readily available?) and I need to find out why the earth to the master cylinder switch isn't earthed?

Edited by yorkshirechris, 14 April 2009 - 11:03 PM.

[Disco Dan]

Here is another wire diagram for earlier models pre ignition.

(same as the first one just from a different manual so in less technical format)



36: Brake fluid test switch with built in light, on dashboard.
65: Brake fluid switch on master cylinder.



The wires your talking about may only register as being 'earth' on your multimeter when the switches are in the 'on' position.

Connect the two spades together off your fluid cap and test again. Then test with the test switch 'on' and also test with both 'on'. You will see what wires are going where and doing what then !

Edited by Disco Dan, 14 April 2009 - 11:12 PM.