308 brake failure light

308's have a brake failure light ???

Mine's a euro , , I guess they don't have one .

 

Could be the handbrake lever switch. The "junction box" has a valve in it and this could be sticking.

 

It is most likely the brake bias valve . The contacts are touchy and sometimes when you hard brake or if you do a brake bleed or install new pads you shift this valve spool and it turns the light on. Go under the car and remove the front bottom plate and pull the connector off to see if the light goes off. If so then you need to get the valve re-centered. If the light stays on then check the floats in the brake reservoir. One of them may be bad or has sunk because it is full of brake fluid. If those are OK then the last place is the handbrake switch. Good luck.

 

Have you checked your brake fluid? Both chambers of the reservoir have a level switch which, when low, light the brake failure warning bulb.

 

I posted the first photo in another recent thread, similar to this one.

What had happened with my valve was brake fluid got past the internal sealing of the switch itself, shorting it out and making it activate the light constantly. The pistons in the valve weren't jammed and the braking system worked fine otherwise.

These original units are attrociously expensive (I think $2000+) and only searching the Bosch P/N of the switch turned up nothing. Gerrit Visser, had discovered a Volvo unit would work fine and so I installed one too. I've had no problems with it too and it was less than $200. At the time of replacement, most of my hard lines were getting rusty so I made new ones and replaced them all. If anyone should decide to install the Volvo switch, you may need to make new lines as the layout isn't quite the same.
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I can't find where you have posted info about your 308 such as year model and country it was manufactured for. In many cases it doesn't matter but for brake warning light systems it does.

Most cars simply have that 'brake failure' pink wire to the fluid level and proportioning valve where a ground lights the brake bulb. They also have either a separate handbrake switch and warning light, again where a ground on the line will light the bulb or they combine both handbrake and fluid functions into one 'brake' warning light. And some early cars have an extra relay to light the brake bulb during start. While unlikely to have sticky contacts, it is possible. This function is similar to modern cars which light everything on the dash to insure they haven't burned out.

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HUH? What brake failure light? Show a pic PLEASE. I don't have one.

 

THANX.

I'll check my car.


I may have learned something new today .....

 

Since your car has both brake fail and handbrake lights it eliminates handbrake circuit wiring into the center console. Being a later 308 eliminates the brake test relay as I believe that relay was discontinued mid-1980.

Rizzo, your just having worked on the master cylinder suggests a problem is right there. Removing the pink wire from the proportioning bias switch AND fluid level switch suggests a pinched wire shorting to ground between those master cylinder connectors and the dash light. You did actually remove the wire from the switch, not just remove the switch didn't you?

I just pulled the shroud on my 1980. My fluid level pink switch wire is not easy to remove as a normal connector would be. It actually looks to be soldered to the switch. The pink together with a black wire then goes under the heater air hose. Probably to the bias valve and then into the cabin and is near impossible to inspect at the entrance point. I didn't want to go under the car to access the bias valve switch and wire. SteveK and Peter have good points regarding the bias switch.

Did you actually remove the fluid level switch pink wire from the switch or just remove the switch from the reservoir? Same on bias switch wire. Logic says one or the other is at ground.

FYI, if you want an easier way to check other than crawling in and out of the cabin, turning key on and checing the light...use a troubleshooting bulb probe. Clip the probe's normal ground wire to the positive terminal of the battery, and touch the pink wire with the probe tip. It's like a remote brake fail light and should not light unless there is still a ground somewhere on the pink wire.

 

Good point Paul, I didn't see the part where the master cylinder was removed and reinstalled. If he didn't have the light before the rework and got it after then I would believe it is in the area where the change was made. Also the circuit is different from my 1977. I think my handbrake and bias valve and reservoir are all on the same circuit and lights the same brake warning light.

 

OMG , , it's a good thing my English delivered car never had these warning lights , , , , I'd be half blinded by the bright red light shining in my eyes all the time !! Damn rear brakes took a lot of sorting out.
(The English delivered car didn't have the "SLOW DOWN" lights for each cyclinder bank either.)

 

Can I just leave the wire unplugged ? As my light goes off when unplugged . Braked a bit hard once and the light came on …..

 

Most likely our valve body is leaking internally. Its not a huge expensive job to replace it... In a 308 I'd want to know if you have a pressure drop... I'd recommend fixing it. I had this happen in my 308 back in the 90's... it got really wet and rusted so the contacts just shorted out, and the light was on ...

 

BTW, "Peter" posting above is your regional director for the FCA in Vancouver. You should reach out to him.

 

Peter ? Ahh ok way up at the top . Thanks