57 replies to this topic

[madalicesdad]

Modern cars don't test the switch. Only that there is an indicator.
Which generally is not out of sight by your left knee...

[stuart bowes]

Hang on a sec... I think I've worked out where I'm going wrong here

Bear in mind I'm only working on the loom on a table I don't have the car running in front of me so here's the mistake (I think)

I was assuming there was a light on the dash for brake fluid low which the switch would illuminate.. but now I'm thinking there isn't

I have a 3 binnacle setup by the way

So there's one red light I can see I'm guessing that's the oil warning (just a light no symbol?)

And the brake level warning would only be on the switch which I twigged after reading KTS post

So going back a few steps and starting again..

The point of spiders mod is that red light on the dash will now light up for oil fault OR brake fault or (unlikely, but) both

So I can inform MOT man of this mod if he asks, get rid of the switch, and if required prove it by pulling the lid off the master cylinder and the light comes on

Does that make sense now hopefully I've got the right end of the stick

Edited by stuart bowes, 05 May 2023 - 05:35 PM.

[stuart bowes]

And if that's right perhaps someone can now kindly explain the point of the diode and where on that diagram exactly would you put it

On the black/ white cable before it joins the white/ brown

Or.. join the two together then put the diode after that then into the oil sensor

[KTS]

it seems you haven't quite understood what Spider put forward 

 

on the schematic you'll see that there are two lamps present; one for the oil pressure warning and one for brake fluid

 

as mentioned previously, what the solution does is basically use the operation of the oil pressure switch (..which is an electrical switch..) as a replacement for 'press-to-test' function of the dash switch

 

the diode is needed to prevent the 12v from the oil pressure warning circuit to back feed through the brake fluid warning lamp when the oil pressure switch is open (i.e the engine is running)

 

to answer your previous question :  yes; with that system the brake fluid warning lamp would illuminate when no oil pressure exists

[stuart bowes]

Brilliant thanks so the oil pressure switch closes and completes the circuit when there's low pressure then, and the lamp illuminates, which makes sense

And I've just cut my manky old master cylinder lid in half to check how that works (so gunked up I couldn't get a continuity test) and confirmed the same there, low fluid = closed circuit

So all I actually have to do is totally delete the switch, forget the diode, and add the black and white wire to the brown and white.

So if oil switch closes the red dash light comes on (fault indicated) and if the brake fluid drops low enough, that same light comes on (fault indicated) either way a closed switch has provided earth to the circuit and I get a light

Essentially providing a bypass to earth via the brake fluid level switch

and in the unlikely event of brake and oil fail that circuit just has two earths which makes no odds

Seeing as it's just a red light basically it just means fault, pull over and stop straight away.

I'm sure I can get that past the MOT man and it's provable by taking the lid off the master cylinder and letting the fluid drain from that little capsule to create a low fluid warning

Also with no switch in place it doesn't fall foul of the 'if fitted' rule

Besides which, with mot free time coming up fairly soon it won't be an issue for long

That would leave me happy that I've got a sensible working warning system anyway

Edited by stuart bowes, 05 May 2023 - 06:45 PM.

[cal844]

Don't use the red light on the dash, that's the battery/ charge circuit light. The on you need is the orange light for oil pressure. (assumes that the cluster is in front of driver)

[stuart bowes]

Yeah I was literally just about to update that lol

Having checked again.. oil/ brakes will be orange. Red is ignition light

I took the bulbs out and used my phone torch from behind to check after following the wiring / pcb paths

Edited by stuart bowes, 05 May 2023 - 07:06 PM.

[Spider]

There is a spare bulb position in the cluster.

Depending on the year, it's either at the bottom of the Speedo or top of the Fuel / Temp.

I think some also had a further spare spot in the Tacho.

[stuart bowes]

cheers, but to be honest I'm pretty happy to leave it as it is now, seeing as the lamps are not labelled and have no symbols anyway, what difference would it really make 

 

actually I like the fact that orange is now just a general fault indicator, it's like the EML symbol on modern cars

 

thanks anyway though and appreciate your pointers earlier which led to the solution in a roundabout way

Edited by stuart bowes, 05 May 2023 - 08:29 PM.

[stuart bowes]

Saw my MOT man today for the volvo (passed no issues)

Asked him about this in passing and his opinion was, if the light on the button was lit up he'd check the reservoir. If the reservoir was filled ok he'd assume the sensor failed and just pass the car anyway (assuming of course brakes pass tests)

On his own one he can't remember the last time he pressed it no idea if it works, would be too worried the switch would just break if he tried lol

Uses the usual method as I said right at the start, checking fluids under bonnet on regular basis

His opinion, just lose the switch . Told him already rewired and explained setup as above and he liked the idea and said yeah fair enough

[Ethel]

Simplest was to pinch a Metro handbrake lever which was the same, but with a switch. You could use a brake light switch, courtesy light switch, or any "push to break" switch mounted where the handbrake will open it when it's off.

 

Ignition feed to a brake warning light, then on to earth via your handbrake switch as well a separate earth via the fluid level switch. As a bonus you're reminded when the handbrake is still on.

[PoolGuy]

Why would you not want this?

 

 

Uses the usual method as I said right at the start, checking fluids under bonnet on regular basis

His opinion, just lose the switch . Told him already rewired and explained setup as above and he liked the idea and said yeah fair enough

That's good enough for me. As for "why wouldn't you want it", I (as above) prefer to check safety critical items regularly rather than rely on a potentially unreliable warning system to tell me that something may not be working.

[mbolt998]

 

Why would you not want this?

 

 

Uses the usual method as I said right at the start, checking fluids under bonnet on regular basis

His opinion, just lose the switch . Told him already rewired and explained setup as above and he liked the idea and said yeah fair enough

That's good enough for me. As for "why wouldn't you want it", I (as above) prefer to check safety critical items regularly rather than rely on a potentially unreliable warning system to tell me that something may not be working.

 

I always thought it very unlikely that you could lose so much brake fluid for that light to come on without knowing about it anyway. But maybe you can.

[Spider]

 

 

Why would you not want this?

 

 

Uses the usual method as I said right at the start, checking fluids under bonnet on regular basis

His opinion, just lose the switch . Told him already rewired and explained setup as above and he liked the idea and said yeah fair enough

That's good enough for me. As for "why wouldn't you want it", I (as above) prefer to check safety critical items regularly rather than rely on a potentially unreliable warning system to tell me that something may not be working.

 

I always thought it very unlikely that you could lose so much brake fluid for that light to come on without knowing about it anyway. But maybe you can.

 

 

As Brake Shoes wear, the level in the Reservoir will drop. if they are not adjusted back. Likewise, with Discs, as the Pads wear, the fluid level will drop.

With the Yellow Tag Maters, they way that it's necessary to plumb it up, with the Top Port to the Front Brakes, that has the smallest Reservoir and will in fact run dry before too long with regards to wear - in the case of 8.4" Discs, around 1/4 wear on the Pads in enough. This is why these Master Cylinders are illegal here (Australia).

I'll add too (and yes I tale on board what the MOT man has said), things think these they don't add to cars to increase sales of them, they most likely did this to meet regulations.

[stuart bowes]

That's interesting actually I was having a similar discussion about it with my dad yesterday we were saying obviously barring some sort of leak the only real time the fluid should go down is with pad wear. And we were saying surely though even with bad wear it wouldn't go down far enough to trigger that light

But with what you've said just there actually it corrected us on that point then

My master cylinder does indeed have a yellow tag. I assume that's a global standard then and no difference between your yellows and ours

Edited by stuart bowes, 06 May 2023 - 11:33 PM.