E-Brake Dash Light Not Working

[ratdude747]

Well that is not the Ebrake switch but a low PSI of the normal brake system.

If there is a leak, broken brake line, a valve moves inside that brass part and turns on the dash light telling something is wrong ......... like the brake pedal going almost to the floor was not a clue!

Now to see if the light works when you first turn on the key the dash lights should lite up if good as a test of the bulbs. Same for the fasten seat belt light.

I think you can short the 2 wires and it should turn on the dash light / wiring.

Mine only has 1 wire and I go to ground to test the light / wiring.

The Ebrake did not have a light on the early 80's at least not my 81's

Dave ----

With a properly functional proportionating valve your pedal shouldnt go to the floor with a brake failure. The purpose of the valve is when one circuit ie front or rear develops a leak the valve will be forced to the side with less pressure cutting the fluid off to the rest of the system and maintaining proper pedal pressure on the master cylinder side. If your valve is not functioning correctly then you would have a pedal going towards the floor as that circuit is not building pressure but is simply dumping the pressure through the leak.

It is a big reason why I am hunting down for a NOS unit to replace mine on my truck as there is no way to test them if they are functioning properly or not plus I tried to take the switch out on mine to replace it with a new one I think the switch is bad as my dash light doesnt light up either but the switch broke off in the valve and if I pull it off the truck to try and get the broken plastic out I might as well just replace it.

As far as the lighting up with the key on I dont believe mine does, only one that lights up while the buzzer is going when the key turns on is the fasten seat belt light. I honestly dont believe I ever seen a brake light on our year model trucks light up as a test with the key turned on. I dont think it even does it on my '78 Mercury either.

Or, you can do what I did and upgrade to a newer master cylinder with a float and reed switch, and wire that switch in parallel with the proportioning valve switch:

https://forum.garysgaragemahal.com/Master-Cylinder-Upgrade-Part-Numbers-tp120071p120422.html

I had a leak before the proportioning valve (crossthreaded/malfunctioning master cylinder connection) and it caught it. Go figure.

[Rusty_S85]

I don't remember when the park brake switch was added, but I think it was '84. Prior to that there was no indication that it was on so you wanted to put it ON so the truck not moving was the clue.

As for indication that the bulb is working, that comes as you turn the key to Start. You can see that in the schematic below from the '85 EVTM, and that function was in all years.

https://forum.garysgaragemahal.com/file/n124108/1985-etm-page89-modified.jpg

Looking at the wiring diagram you posted I just cant see how the buzzer is turning the brake light indicator on.

#3 on the timer that goes to the fasten seatbelt light is providing power to the fasten seatbelt light which then goes straight to ground. It is pulsing the positive side to illuminate a already grounded bulb.

On the brake warning indicator you have C208 which is ignition hot through a fuse in the fuse box which piggy bags off that terminal to #4 on the timer to provide key hot power to the buzzer/timer. The other wire on C208 at the bulb goes to the dual brake warning switch which goes straight to ground with the switch breaking the circuit.

How exactly does the timer on this schematic provide a ground for the brake warning light to illuminate it? The brake warning light only comes on when it is given a ground while the seat belt light is constantly grounded and is provided power through the timer?

[Rusty_S85]

Or, you can do what I did and upgrade to a newer master cylinder with a float and reed switch, and wire that switch in parallel with the proportioning valve switch:

https://forum.garysgaragemahal.com/Master-Cylinder-Upgrade-Part-Numbers-tp120071p120422.html

I had a leak before the proportioning valve (crossthreaded/malfunctioning master cylinder connection) and it caught it. Go figure.

I thought of doing that upgrade just for the cleaner look of it and the ability to check brake fluid level without popping the cap off. I just would have to verify the brake warning circuit is functional on my truck before I could do that upgrade with the low level float. The ones Ive seen are a two wire design and all I would have to do is splice into the key hot side on one wire and run the other wire directly to ground so the float grounds the key hot wire no different than the warning switch on the proportioning valve.

For me its something that is low on my list as I never had it hooked up and drove my truck daily. The brakes were just something that always worked and never gave an issue. But now after sitting this long I will have to replace wheel cylinders, calipers, bleed the system out. maybe even replace the master cylinder but as far as I know its original to the truck and I am afraid a new one might give me the squishy brakes that I see on so many trucks that mine doesnt have.

[Gary Lewis]

I don't remember when the park brake switch was added, but I think it was '84. Prior to that there was no indication that it was on so you wanted to put it ON so the truck not moving was the clue.

As for indication that the bulb is working, that comes as you turn the key to Start. You can see that in the schematic below from the '85 EVTM, and that function was in all years.

https://forum.garysgaragemahal.com/file/n124108/1985-etm-page89-modified.jpg

Looking at the wiring diagram you posted I just cant see how the buzzer is turning the brake light indicator on.

#3 on the timer that goes to the fasten seatbelt light is providing power to the fasten seatbelt light which then goes straight to ground. It is pulsing the positive side to illuminate a already grounded bulb.

On the brake warning indicator you have C208 which is ignition hot through a fuse in the fuse box which piggy bags off that terminal to #4 on the timer to provide key hot power to the buzzer/timer. The other wire on C208 at the bulb goes to the dual brake warning switch which goes straight to ground with the switch breaking the circuit.

How exactly does the timer on this schematic provide a ground for the brake warning light to illuminate it? The brake warning light only comes on when it is given a ground while the seat belt light is constantly grounded and is provided power through the timer?

The timer doesn't have anything to do with the brake warning light. But the ignition switch has a contact that grounds in Start and lights the light via Ckt 977 and the Dual Brake Warning Switch.

[Rusty_S85]

The timer doesn't have anything to do with the brake warning light. But the ignition switch has a contact that grounds in Start and lights the light via Ckt 977 and the Dual Brake Warning Switch.

Then in that case it only illuminates when the key is turned to the start position and not when the key is turned on which is how the seat belt light illuminates.

[Gary Lewis]

Then in that case it only illuminates when the key is turned to the start position and not when the key is turned on which is how the seat belt light illuminates.

Yep.

[Rusty_S85]

Yep.

That would make sense then why mine doesnt light up seeing as the switch is broken off and the connector is not plugged into anything. For the check to function the two wires would have to be jumpered together for the key to provide the ground for the hot wire to illuminate the bulb as a check when cranking.

Now I am tempted to see if I can get a torqs bit jammed into the plastic threaded base to unscrew it on mine when the engine is out so I can put a new switch in and see if that solves the issue I have with questioning if the circuit is functional in the first place.

[Gary Lewis]

That would make sense then why mine doesnt light up seeing as the switch is broken off and the connector is not plugged into anything. For the check to function the two wires would have to be jumpered together for the key to provide the ground for the hot wire to illuminate the bulb as a check when cranking.

Now I am tempted to see if I can get a torqs bit jammed into the plastic threaded base to unscrew it on mine when the engine is out so I can put a new switch in and see if that solves the issue I have with questioning if the circuit is functional in the first place.

Larry - Didn't you put a new switch in the brake warning switch?

[ratdude747]

That would make sense then why mine doesnt light up seeing as the switch is broken off and the connector is not plugged into anything. For the check to function the two wires would have to be jumpered together for the key to provide the ground for the hot wire to illuminate the bulb as a check when cranking.

Now I am tempted to see if I can get a torqs bit jammed into the plastic threaded base to unscrew it on mine when the engine is out so I can put a new switch in and see if that solves the issue I have with questioning if the circuit is functional in the first place.

Larry - Didn't you put a new switch in the brake warning switch?

I added the the new switch in parallel with the proportioning valve switch.

That circuit in effect has four contacts in parallel on my truck:

-A contact of the START position of the ignition switch (lamp test)

-The E-brake switch (which the OP doesn't have)

-The proportioning valve switch

-The Master Cylinder switch (which I added)

However, upon further review, the way that's done is a bit "unusual":

As the igintion switch contact runs through the shorted portion of the proportioning valve switch (the actual switching element shorts to ground); with the switch unplugged, the ignition lamp test will fail. Similar to the "newer" master cylinder switch, which (in it's intended application) has two of three contacts shorted together to do the same thing, only as an input to the ABS module, not as part of the ignition lamp test.

 

[Gary Lewis]

I added the the new switch in parallel with the proportioning valve switch.

That circuit in effect has four contacts in parallel on my truck:

-A contact of the START position of the ignition switch (lamp test)

-The E-brake switch (which the OP doesn't have)

-The proportioning valve switch

-The Master Cylinder switch (which I added)

However, upon further review, the way that's done is a bit "unusual":

As the igintion switch contact runs through the shorted portion of the proportioning valve switch (the actual switching element shorts to ground); with the switch unplugged, the ignition lamp test will fail. Similar to the "newer" master cylinder switch, which (in it's intended application) has two of three contacts shorted together to do the same thing, only as an input to the ABS module, not as part of the ignition lamp test.

Thanks, Larry. I understand.