Brake Failure light

Do we assume that you have checked the brake fluid? Also are you sure that the 2 floats in the brake bottle are floating and not half sunk. If this happened after you played with the radio then you should continue to search around to see if you have grounded the wire from the brake warning light. Last would be the brake failure switch under the front of the car. Considering that the brake fluid is full and the floats are OK then I still would check the light circuit.

 

See -- http://ferrarichat.com/forum/showthread.php?t=147994

 

Check out this site... http://www.ferrarichat.com/forum/member.php?u=1897 posted by "Ferrarimechanic" on 4/25/07. Good article!!! I just went through this last weekend with my '79 308. Got under the front of the car...pried up the switch contact assembly out of the "imbalance valve" with a small screwdriver - that's what I call it!...gently scrubbed off and cleaned up the "tuning fork looking contacts", blew out any moisture in the "imbalance valve" cavity where the switch fits...there was moisture in it...hoping it wasn't brake fluid!!!...replaced the clean switch, and the light is out! Brakes feel as good as before...no problems, so I suspect moisture and gunk buildup of 30 years were causing the problems. The article was the source of my info. Good luck.
Dan

 

Brake failure warning light comes on under 3 conditions.
1) Key is in the starter position energizing the brake relay coil, grounding the low side of the light. Purely a test for the integrity of the lamp.
2) Second is when brake fluid is low, energized by reservoir switches.
3) When the brake balance differential pressure switch is energized indicating a difference between front/back circuits.

The wires in question are all pink.

I just went through this and it was my relay.

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308 Wiring Diagrams
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Very helpful...my 83 was doing this exact same thing just this weekend...only when hitting the accelerator though. I'll be checking the reservoir when I get home.

-BJ

 

Thought I'd resurect this thread as my brake failure light comes on intermittently & not full bright and not always when I apply the brake.
1) The master cylinder & Power assist unit was replaced 4 years ago and seems fine
2) The fluid level is fine
3) I've cleaned the resevoir contacts
4) I've cleaned the differential pressure switch contacts (this cured the problem last time).

But the light still comes on dimly.

How do I get the sensor out of the differential? As suggested above by prying it out?
also, where's the relay that was mentioned above?
thanks.


btw: "Check out this site... http://www.ferrarichat.com/forum/member.php?u=1897" points to the user's info, not a web site. somebody have the correct link?

 

Just use a small screwdriver to pop out the sensor. It is simply a small piece of copper I think. Clean it well and also spray some cleaner into the hole and clean it with Q-tips. It will be pretty grimy in there.

 

ok so i I've cleaned the differential pressure switch contacts the fluid level is fine , floats in m/cyl are ok.... dash light still on so i pulled the press switch out of the block contacts are clean my dash warn light still on what the ????????????

 

My differential switch contacts looked ok...but it turned out to be them. a carefully controlled brass dremel brush proved effective on the three contacts.
Problem gone

 

Brake failure relay is the last relay on right, top row of the relay panel, sometimes marked as 'F'.
The relay is only used to turn the failure light on briefly when the ignition key is in the start position.
It's not used when the brake reservoir level OR hydraulic fluid pressure diff contacts engage to ground.
Wires for that circuit are pink.

Also available on the wiring diagram. http://www.ferrari308gtbi.com/
A partially lit lamp indicates one of the fluid switch isn't clearing but has partial short. Removing
the connector of each in turn will indicate and prove the culprit.

 

I changed my brake fluid & the Brake failure light wouldn't go out. I figured it was probably just the float on the cap.
shorted the leads together & the light went out.
Took the cap off & noticed it was kinda grimy

so I carefully took it apart, cleaned everything, cleaned the contact spades & re-assembled. below are the pics of it apart for future reference.
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careful with this. there's a couple parts that will break right off.

 

Any photos of this switch and cleaning the contacts?

 

Hey Clyde, Did it resolve the problem?

I had an issue with the boxer after changing the fluid last Fall and the breaks working. The brake failure light would flicker after driving a bit and I'm not even touching the brakes, and then come on. Then would go out, then would come on. Rebled system 4 times and checked the fluid level senders, proportioning valve and which did not resolve. Finally after pulling and checking the proportioning sender for a second time - tested okay - I just changed it as they are cheap and it resolved the issue. Light has never come back on and the brakes are excellent.

Worst feeling in the world is seeing that light pop on even when you have good brakes.

Hope yours isresolved.

 

Sorry, no. I used a fiberglass pen on the contacts. Liquid spray solvents didn't do enough.
BTW: the "switch" is two nibs on the inside of the top and that metal washer. That's it. Gotta love the simplicity.

Yes it did. Woo Hoo!

A few years back I had symptoms you described. It turned out to be the contacts on the brake proportion valve near the steering rack. Pop off the spade connector, clean, reconnect & go

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