Should i unscrew the center plug or sensor  marked as "1"  in the bottom drawing and clean it with a brush and electronic contact cleaner?

Yes (it's a "bullet" connector and just pushes on, doesn't screw on).  And clean the inside of the connector that attaches to it also. 

Once you get the connection all cleaned up and reattached, that light will probably get brighter.  If it does, you have a problem with a brake circuit or a faulty pressure differential switch that will need to be replaced.  The switch inside completes a ground circuit for the warning light.  It can only do so if the shuttle inside is pushed out of it's neutral position by a brake circuit imbalance.  

It looks like the electrical part is right, doesn't it?  The switch is doing its job, there seems to be a pressure differential.  The brakes might need bleeding.  Some people say that the 240Z switches need to be reset after the valve moves.

I could get my 280Z light to go off, when I had a problem, by pumping the brakes to remove the differential.  That was a clue, for me.

 

On 10/3/2018 at 7:42 PM, Patcon said:

That most likely means you have problems with your brakes. One circuit is probably not working. Are your stopping distances longer than you think they should be?

Already cleaned both the female plug connetor and the tip of the male connector with a diamond grip terminal cleaner. Light still shows up a little dim when plugged. Should i get a wrench to clean the innards of the valve?

The 240z sensor does NOT have to be manually reset, it re-centers itself. My wheel cylinders were frozen with rust and the brake warning light would come on when the brakes were applied and go off when brake pedal released. I replaced the wheel cylinders and that cured the light coming on. The light works fine for the park brake. From the original description it sounds like the dim light is on all the time when the ignition is on regardless of the brakes being applied or not. My guess is a short in the sensor.

Edited October 8, 20186 yr by w3wilkes

Where is the sensor? Is there a way of opening the valve?

The sensor is what you referenced as "1" above. It's in the valve you provided the diagrams of. I know there's at least 1 other thread on that valve and how it works.

 

Do you have a multimeter?  You can test the switch (what you are calling the sensor) by removing the wire and testing for continuity between the male bullet connector and ground (the thing you have circled in red in the picture above).  It should have NO continuity (open circuit) if the shuttle inside is centered properly. 

If it has any continuity then:

- There is an imbalance in the brake circuits

- The switch is stuck and off the neutral position

- The switch is defective

The fact that the light only illuminates when the wire is attached shows the "fault" comes from the switch itself, not a ground fault in the wire.

The Factory Service Manual advises against repairing this device - but that was back when they were still available from dealers.  I would probably source another one - failing that, There's a cross section picture above (Figure BR-12 Warning Light Switch)  that shows how it could be disassembled.

Edited October 9, 20186 yr by cgsheen1

Okay. Now that i will have to bleed the brakes shouldnt i get a new set of brake pads and brake drums for the rear? Can you advise on this properly?

4 minutes ago, jalexquijano said:

Okay. Now that i will have to bleed the brakes shouldnt i get a new set of brake pads and brake drums for the rear? Can you advise on this properly?

No need to change pads and rear brake shoes UNLESS they show significant wear or you notice a brake squeal (metal on metal) when applying brakes.  Don't make extra work for yourself.

Dennis

Bleeding only?

23 minutes ago, jalexquijano said:

Bleeding only?

Only if you're tried, and eliminated, all the other suggestions like electrical grounding somewhere in the wiring.  Pads & shoes won't make the light come on unless they're very worn and brake fluid level is low.

Dennis