Brake warning light. I don't get it... (1 Viewer)

[RemcoSeegers]

Below the scheme of the wiring for the parking brake. I find all the wires back on my car. But, I have a question about the scheme, it does not make sense to me and also does the behavior when I connect make no sense.

The light gets feed from LR. Then continues through either one of the switches, the one for the pedal when a circuit does not work and the pedal goes low or when the handbrake switch is on. Until here, no problem. But, on my car there is also the brake fluid switch. I assume that is the 'Brake Warning Switch' on the scheme. And here is my problem. The only way the circuit can work is when this switch is closed (meaning, too low fluid). The question is, how can that be possible? That would mean that if my fluid is ok, the circuit is broken and the light can never go on, not for the handbrake, neither for the 'too low pedal' switch. Who can enlighten me here?

Thanks!

 

[Malleus]

It may be that the problem is the "shorthand" that Toyota used in this schematic. Although the various switches are drawn as though they would all be connected in a continuous circuit, that is to say, a loop, that is actually not the way the wiring is routed. Each of the various switches are linked to the warning light, and their power source, individually. This schematic should be considered to be a logic diagram, and not an actual circuit description.

Toyota also supplied a wiring diagram with the circuit diagram, which illustrates how the individual components are connected to the the wiring harness. It is this diagram that would illustrate how each of the various brake fault switches actually work.

HTH

 

[RemcoSeegers]

Strange... well I can easily fix it by connecting the lowest RW to ground and make another switch (brake fluid) over the drawn switches. Then the light goes on for any of the 3 reasons.

 

[45Dougal]

Its just a simple switch circuit.

The brake warning switch is a pressure switch (2 actually in parallel).

When you release the pedal, the pressure switch is closed, but the brake pedal switch is open so no light.

When you then pull the handbrake, the light comes on because both switches are closed.

When you push the pedal, the pressure switch should open. If it doesn't, then the light comes on to warn you that one of your brake circuits has low pressure.

The toyota diagram is actually wrong - the second pole of the pedal switch is actually Normally Open, not Normally Closed.
Everything else is right.