Brake Warning light on dash stays on.

[maj75]

87 Supra, factory turbo/5 speed

I have the brake warning light which stays on. It gets brighter if the handbrake is raised. The brakes work good and the master cylinder is full. Is there a way to test the brake fluid level switch? Is there anything else that might cause the light to stay on? Can the brake level switch be bypassed? I think that the light being on might be causing the cruise control to not engage.

 

[MKIII VIXEN]

Check the brake lights.

 

[S.A. supra]

^ yep +1

 

[Koenigturbo]

short

 

[S.A. supra]

Or you might also check the white box that is next to the drivers side tail light. I forgot what it's called. When it would rain, water would leak in between the tail light and the body and my light would also come on.

 

[SupaMan]

Guys (and vixen ) hes talking about the handbrake light not the tail lights light.

The fluid level sensor could be bad?

 

[maj75]

You are correct, sir!

I measured the level sensor and got 16 ohms /39ohms at the empty and full positions. However, I don't know the correct values. Connectors are good, no corrosion and wiring harness is virgin.

 

[supraguy@aol]

I think you're right about the cc not working when that light is on.
Go to the junk yard, get a replacement cap for the resevoir.

 

[maj75]

Could someone test their master cylinder level sensor to see what values they get, before I buy a replacement?

 

[maj75]

Problem solved. I got a master cylinder cap from a member (discontinued from Toyota) and at the same time got the Toyota manual which shows that the level sensor in the brake master cylinder measures no resistance when full and is open when in the low position. I tested the cap I received and the values were right on. Replaced cap (wires a bit shorter than my original, must be off a later model) plugged in connector and the brake warning light on the dash went out! Drove the car and sure enough, the cruise control was now working!

If your warning light is on but the master cylinder is full, your level sensor is bad. A temp fix would be to cur the wires and connect them together. The warning light will go out and your cruise will work. You have not lost anything since the level sensor wasn't working anyway. The E-brake warning light will continue to work.

 

[jetjock]

....the level sensor in the brake master cylinder measures no resistance when full and is open when in the low position.
....A temp fix would be to cut the wires and connect them together....

You have all that backwards...

 

[maj75]

You have all that backwards...

Check you sensor, check the Manual...

When the sensor drops, it breaks the connection to "ground" and the light turns on.

 

[jetjock]

Not on my car, not in my manual, and that's not how it works according to the schematic but OK, if you say so.

Btw how can it have no resistance when full and be open when low? It's the same thing...

 

[maj75]

Not on my car, not in my manual, and that's not how it works according to the schematic but OK, if you say so.

Btw how can it have no resistance when full and be open when low? It's the same thing...

You are correct. It is an open circuit when full, closed to ground when empty.