Sniper_X

I have a 1995 FD.

The break warning lamp in the instrument cluster stays on even after I released emergency brake and even though the brake fluid reservoir is full of fluid.

I have tested the brake fluid reservoir switch and I can assure you it's working perfectly.

here are the other symptoms:
1) when I pull the emergency break up, the light gets brighter, when I release it it gets very slightly dimmer.

2) when I unplug the brake fluid reservoir sensor under the hood, the light turns off completely and returns to otherwise normal operation.

The emergency brake switch has been tested and works perfectly.
This is evidenced by the fact that when I lift the brake handle the light brightens and when I will lower it dims.

I have tested the brake fluid magnetic switch both in and out of the brake fluid reservoir and I can assure you it's working perfectly.

What in the world could be going on here?!

I have reviewed the factory service manual and I cannot see any way this could be happening.

Thoughts?

bajaman

I suspect some sort of short in the wiring AFTER the switch. You know the switch is good so, not too many other possibilities. I'd do a ECU reset (assuming you are stock) by disconnecting the positive terminal on the battery and then depressing the brake pedal 3 times. If this doesn't cure the problem, time to get out the ohm meter and start checking for resistance/continuity on the e-brake wires.

jm2fd

If you're sure the level switch is working properly (and to me it sounds like the switch is stuck closed) then the only other possibility is that one of the wires to either the parking brake or fluid level switch has shorted to ground.

Sniper_X

Okay, so...

I know that there is nothing wrong with the fluid level switch.
Its been tested out of the car, and no problems there.

Its odd that the light only comes on solid when i plug in the sensor though.

Considering that the RX7 activates circuits by grounding them, you would think that if there was a short in the harness, that the harness would indicate continuity to ground (or VERY low resistance) on BOTH legs of the harness at the fluid level sensor, but it does not.

It tests out as good, as per the FSM.

Can anyone think of a way someone could intentionally CAUSE all these symptoms, yet cause this issue?

'Cause I'm frikkin stumped.

Sniper_X

Okay,

I have taken apart the instrument cluster and the center console.

The brown/yellow wire in the cluster that grounds the brake lamp is supposed to ground ONLY when the E brake is up, or the fluid level sensor is tripped.

I have verified that when I unplug the ebrake ground wire and the fluid low switch, it is indeed NOT grounded.

I have also verified that it does ground when the ebrake is pulled with the fluid low switch disconnected.

I have also verified that when the fluid low switch is connected and the ebrake is not, that it grounds only when the magnetic switch inside is closed by the fluid float.

So they both work independent of each other as expected.

They also work as expected when they are all connected.

Here is the freaky part...

Even though the fluid switch works perfectly, and is NOT engaged, when I test Across the IGN+ and the brown/yellow brake ground, I get +12.5 volts when the fluid switch is in circuit.

But remember, the fluid switch isn't closed, and there is no ground at the brown/yellow wire!!!!

So, I checked to see if I was just getting a very low resistance value instead of 100% ground, and I'm getting infinite ohms resistance with the switch and circuit. (in other words, no connection to ground)

So, how in the WORLD and I able to measure 12 V between a wire that has no ground, and the positive 12 V ignition lead?!!!!

Sniper_X

So because the problem only exists when I connect the low fluid switch in circuit, I took the switch inside, pushed out the pin, and pulled out the board.

I found what I expected, and is what the FSM diagram shows.

One magnetic reed switch
One resistor

The resistor reads at .508k ohms.

the reed switch works as it should.

Yet, when I place this switch in-circuit, with no magnet, the switch is open, therefore it's not grounded, I still can measure +12v when I touch batt+ and use this as ground!

HOW?!

How is +12V getting to ground?

through this 5,000 ohm resistor?!!!

Sniper_X

Also, WHY is there a resistor at all?!!!

Sniper_X

So after some research I believe the resistor may be involved in preventing noise on the 12 V circuit or noise on the ground plane.

It also may have something to do with the circuit that you can see very close to the brake lamp represented in the diagram I have attached.

Someone take a look at this diagram and tell me if you can expand on why this resistor is sitting across the Reed switch?

tampafd

a guess would be that the switch is used on another car/application where it is monitored--- a resistor across the terminals will allow open circuit detection by another component

does the bulb check work?
does it work without the resistor installed?

Sniper_X

Yes, the system works perfectly now that i lifted and insulated one leg of the resistor.

I agree that is should be part of some circuit, however, it's not for another car i bet. Looking at the diagram you can see that the transistor/diode circuit is surrounded by resistors (including the one i took out of circuit.)

Anyway, my guess is that since I'm using an LED as a bulb here, somehow, even with a 5000ohm resistor in circuit, it lights the LED - even though it has been designed to act like a 12v bulb.

I dunno. still stumped as to why this is like this, but it's working now with this "hack".

JM1FD

iTrader: (1)

What's the logic in using an LED in an application like this where the color and intensity of the light is modulated by the red "filter" that has the brake stencil on it?

Sniper_X

I don't understand your question.

It works just fine, and there is no "modulation" of the light.
(Where modulation means "varying the intensity of something")

What do you mean?

JM1FD

iTrader: (1)

The little red piece of plastic between the bulb and your eyes modulates (Where modulate means "change the intensity") the output of the bulb in both color and intensity.

To me, there's 4 reasons to retrofit an LED in an automotive application: color, intensity, response time, heat.

The color and intensity are changed by the red plastic, the response time is irrelevant, and this bulb would rarely be on long enough to build up any appreciable amount of heat.

So...phrased another way, what advantage did you perceive when you put an LED in this particular socket?

Sniper_X

I thought this might be your actual question, but When you tarted talking about modulation I was unsure of your point.


Anyway, in your list of reasons for putting in an LED, you left out the maintenance aspect of it.

I've replaced all of the lights in my dashboard with LEDs to avoid having to change them in the future.

As far as the color goes, you have to carefully select your LEDs and not just put LEDs in without a plan.

Originally, these bulbs are installed in various wattages, therefore to maintain the right brightness, you have to select your LED based on power output.

Second of all yes, there are colored lenses in front of them, so to avoid washing out the color you need to select the LED color based on the color of the lens.

But overall, the main reason for switching to LEDs is to avoid having to go back into the dashboard and change the bulbs.

This is done quite often, and in fact it's just about the only form of illumination in any car today.

JM1FD

iTrader: (1)

Ah. That makes more sense. Bulb life didn't even cross my mind, probably because I've never had to replace any of mine.