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I was looking at the electrical wiring diagram for my truck, and i am trying to make sure i am understanding correctly..
The switch on the brake Equalizer ( located below the master cylinder , looks like a distribution block ) this switch grounds to make the BRAKE light up on the Instrument panel is there is a brake failure of some sort, and then there's another connection that goes to the ignition switch.. Is this connection to the ignition switch like a test feature when starting the vehicle ?
If it is, then i have an issue somewhere. The BRAKE light , lights up if i ground the connection at the distribution block, but there's 2 wires both of which should be connected together.
from what i gather the body of the switch is the ground..right now the BRAKE light only lights up if 1 wire is grounded..if i ground the 2nd one, nothing lights up and the light does not light up when starting the engine.
Is there a place that these 2 wires connect (on the Distribution block ) according to the wiring diagram they do.. I'm guessing somewhere in the harness. But no idea where.
I believe the switch on the proportioning valve is always supplied 12v and is grounded to close the circuit and light the brake lamp. It is grounded by movement of the main valve piston, which pushes the indicator up into the housing and closes the circuit. I don’t recall the valve body being the ground or the lamp would be on all the time.
The circuit has a proof feature for the brake light. When you move the key to Start, the lamp should light.
I’m not sure I follow your wire concerns. Maybe a few pictures would help.
No clue what year truck you have, so I just picked a 1986 diagram below. The proportioning valve is not fed 12v. Only the light bulb is fed 12v any time the key is in run.
If there is a problem in the brake system, the proportioning valve grounds the wire which turns the light on, since it will have 12v on the other side of it. The second wire is just the bulb test wire. It is grounded by the ignition switch during cranking.
P.S. The brake light switch is also lit by the parking brake assembly.
Sorry, I forgot.. I have a 1981 F100 Ranger.
I had a wiring diagram, but it is slightly different than the one I see here.
Also my truck does not have a parking brake switch, which i thought is strange. I see no switch or wire to even use for the parking brake. even tho it shows on the diagram.
Ok, so I am thinking my issue might be somewhere between the brake warning switch and the ignition..
Thanks. I'll check that out more tomorrow ( Weather permitting )
Good news on another issue. My seat belt buzzer was INOP. after testing things, it came down to a dirty switch in the seat belt buckle.. Odd that there isn't one in the passenger side.
But i guess they were more concerned with the driver back then.
The BRAKE light , lights up if i ground the connection at the distribution block, but there's 2 wires both of which should be connected together.
Originally Posted by dacflyer
from what i gather the body of the switch is the ground..right now the BRAKE light only lights up if 1 wire is grounded..if i ground the 2nd one, nothing lights up and the light does not light up when starting the engine.
What is the actual issue you're having? The Brake light is on when it is not supposed to be, or it is on all of the time?
Did you check the switch in the brake prop valve? Is it closed?
Going by the grounding tests you're describing above, the wiring is correct.
If that switch is closed, then there is a problem with the brakes or a problem with the prop valve itself.
I removed that prop valve on my truck when I installed a later model (1987-1991) master cylinder. I connected the original two wires to the N/O contacts of the float switch in the master cylinder. This way my Brake light will illuminate if my brake fluid gets low.
No clue what year truck you have, so I just picked a 1986 diagram below. The proportioning valve is not fed 12v. Only the light bulb is fed 12v any time the key is in run.
Thanks for correcting me, I was riffing on the fly and thinking the switch had 12v when it just completes the ground was stupid.
Originally Posted by dacflyer
Sorry, I forgot.. I have a 1981 F100 Ranger.
I had a wiring diagram, but it is slightly different than the one I see here.
Also my truck does not have a parking brake switch, which i thought is strange. I see no switch or wire to even use for the parking brake. even tho it shows on the diagram.
My 80 EVTM also shows a parking brake switch but no such animal exists on my pedal assembly anywhere. It appears the engineers got ahead of the assembly line by a couple years.
Rembrant >> What is the actual issue you're having? ---------------------------------------------------- The BRAKE light does not light when starting the truck. It does come on when i test it at the valve.
The Brake light is on when it is not supposed to be, or it is on all of the time? ------------------Not on when you are starting the truck
Did you check the switch in the brake prop valve? Is it closed? ---------------------------------------The switch is fine..
Going by the grounding tests you're describing above, the wiring is correct.
Sorry, I forgot.. I have a 1981 F100 Ranger.
I had a wiring diagram, but it is slightly different than the one I see here.
Also my truck does not have a parking brake switch, which i thought is strange. I see no switch or wire to even use for the parking brake. even tho it shows on the diagram.
Nether of my 81's, Ranger & Custom, had a park brake switch / wire or light.
I just plugged the belt wire in but I don't remember any wires to the belts? I want to say it is a seat bottom switch as I think that's were the wire goes.
I did not get the buzzer working after I plugged the wires together and I did see the red box buzzer when I had the dash pad off to install a clock.
Dave ----
btw my brake light comes on when I first turn the key to on.
I think the second page said if it doesn't go through the self test then it'll be the contacts on the printed circuit on the back of the cluster. I wouldn't stress it too much since it lights up when you ground the switch. Maybe just verify that still checks out every month or three.
I think the second page said if it doesn't go through the self test then it'll be the contacts on the printed circuit on the back of the cluster. I wouldn't stress it too much since it lights up when you ground the switch. Maybe just verify that still checks out every month or three.
Why even go thru all the work?
I don't need a light to tell me the brake pedal went to the floor!
I think that is just so stupid!
Same goes for the parking brake. If it worked as it should you should not be able to move the car / truck!
Now I will tell you it dont hold for sh** in reverse!
I have had other cars & trucks do the same but once trying to move forward you knew something was up.
Dave ----
Fuzzface >>Why even go thru all the work?
I don't need a light to tell me the brake pedal went to the floor!
I think that is just so stupid!
I was just trying to get things in working order..
I need to make another post or search for brake issues.
But as far as brakes go, I've replaced everything, and bled the brakes, but they still feel mushy.
Maybe i need to bleed them a 2nd time ?
Replaced the master, booster, new pads all around. still same rotors and drums tho. could they be bad even tho they look fine ?
Why even go thru all the work?
I don't need a light to tell me the brake pedal went to the floor!
I think that is just so stupid!
Same goes for the parking brake. If it worked as it should you should not be able to move the car / truck!
Now I will tell you it dont hold for sh** in reverse!
I have had other cars & trucks do the same but once trying to move forward you knew something was up.
Dave ----
Idk, what if the back brakes are great and the front has a leak, still get full pressure to the rear, would you notice the fronts not working?
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