Brake warning light

[ron32966]

The front reservoir went empty. I refilled the reservoir, bled the reservoir & wheels; the light still won't go out. How do I reset the light? This is on a '77 280z. Thanks for any help out there. Ron

[Arne]

First question: Did you determine why the front reservoir went empty? Your brakes are a sealed system, and brake fluid doesn't go anywhere. Especially so for the front reservoir of a 280Z, which supplies the rear brakes. Simply filling and bleeding will not fix the root cause - you need to determine where the fluid went. In this case, the warning light may still be trying to tell you something is still wrong.

On the other hand, if you have already truly remedied the root problem, you may need to bleed and reset the warning light switch in the distribution block under the master cylinder. I don't know the exact procedure for this on your 280Z, my FSM only covers '70-71 240Z.

[sblake01]

There is no reset procedure. The light indicates, low fluid, or emergency brake on. There's a fluid level switch in each master cylinder cap, and a switch on the emergency brake lever bracket. There is also a brake warning lamp check relay located under the passenger seat. Facing the front of the car it's the one on the left. The other is the floor sesnor relay if you have a catalytic converter equipped car. Check the switches in the caps first and make sure that the floats aren't stuck. If they're moving freely then check the wires for continuity while moving the floats up and down. If they have continuity then check the emergency brake switch. I've never seen the relay go bad but I guess it's possible.

[Arne]

Stephen, there is also a pressure differential switch on the distribution block under the master cylinder. The switch has a single wire to it. It will light if there is a significant difference in fluid pressure between the front and rear circuits. I'm not sure about our Datsuns, but on some cars once that switch has been tripped, you have to relieve pressure in the other circuit while pressing on the pedal to "re-center" it. This is assuming that the root cause has been repaired, of course.

[Z Excellence]

The only way I could get the light to go off on my 76Z after I found the leak was to replace the switch on the pressure dif block under the master cylinder. I bought a used one and it has worked fine.Hope this helps.This all hapened a year ago and it has been fine ever since.

[sblake01]

That may be true for a 240Z or even an earlier 280Z but not on a 77-78 280Z which has a three way connector in the in the area that you speak of since the warning switches had been moved to the master cylinder caps.

[Arne]

Stephen, you may be right. But I've seen info that stated the switches in the caps started in '78, while the pressure-type switch was used from '70-77. Since the original poster says his car is a '77, my info may still be valid. Or not, as I can't swear to it, and don't have access to a '77 280Z to check.

[sblake01]

Well, I have a 78 which doesn't have the pressure switch but my info above came from a 76 and a 77 FSM. I also couldn't swear to it for a 77 or any other 78 besides mine but that's what the books say.

[Arne]

The parts CD is not conclusive, but makes it sound as though the '77s should still have the switch. It is listed as 46100-N4200, ASSY - SWITCH BRAKE INDICATOR, start date 08/76. No end date is listed.

So Ron, I guess my final thought on this then would be to see if your car has a single wire connecting to the distribution block under the master cylinder that all the brake pipes connect to. If it does, I'm going to bet that it has tripped. If it doesn't have that part, check the fluid levels and the switches in the master cylinder caps.

[sblake01]

Just pop the hood and look. If you have the wired fill caps, no need to look for the switch below. Datsun does have a way to keep things interesting with their publications which seem to contradict one another.

[Arne]

Datsun does have a way to keep things interesting with their publications which seem to contradict one another.

Oh so very true...

[WingZr0]

I found that 3 prong plug (left hand side) disconneted under the Passenger seat yesterday and plugged it in to see what happened to see if it was the Fuel pump relay or not.

My brake warning light worked fine evertime I used the E-brake untill then and now it won't turn off. Now when I unplug the connector the Warning light will not light up even when I use my E-brake even though it worked just befor.