Brake Lights not working.

[Spool]

I've said it before, but I hope you know how grateful I am for your help.
You are teaching me plenty. Thanks man.

[Spool]

Hey BD.

The brake switch arrived (with an extra one as well, for free) that I replaced with no successful results.
I then tried the additional brake switch that came with my package with again, no successful results.

I've attempted to have my B+ on the bottom and the top but I have yet to be able to get 12v on the white wire when depressing the brake pedal.

Being a bit determined to figure this one out on my own, I haven't posted but would like to ask one question.
Where is the white wire supposed to go from the brake switch? I had some trouble locating the brake switch in my wiring diagram.

I also picked up a test light, but upon opening it, I learned that to test the wire itself I need to pierce the wire. Is this correct or do I have a cheap test light?

[bd]

The test light you have is pretty common.  Rather than pierce the insulation, probe the terminal.  Pierce wire only when absolutely necessary.

Look at the schematic diagram...



The brake switch is outlined in red. 

The fuse box is illustrated from both the front and back sides.  The fuse that protects the brake lamp circuit is marked with *.  * also marks the "orange" wire terminal of the brake light switch connector.  The orange wire (Ckt 40) is constant B+ supplied from the brake lamp fuse.  The B+ power bus in the fuse box that feeds the brake light fuse is labeled accordingly.  So the lower end of the brake lamp fuse is the "hot" end.

The "white" wire terminal of the brake light switch connector is marked *.  The white wire (Ckt 17) should measure 12 volts whenever the brake light switch plunger is extended (as when depressing the brake pedal).  The white wire runs between the brake switch and the turn signal switch, and is similarly marked * at the turn switch.

What happened when you jumpered "white" to "orange?"  Did the brake lamps illuminate?

[Spool]

Thank you.
Your help allowed me to see it in my wiring diagram.

The bottom of the fuse is the hot side, meaning it's getting it's power from behind the fuse panel through the firewall from a 12gauge wire in ckt2 into the bulkhead. Correct?
If I'm to check this, it invites the question I've been putting off for now. How do I successfully remove my bulkhead connector and fuse panel?
I've only be able to separate them about 2 inches from each other by removing the center screw in the bulkhead and the corner screws on my fuse panel.

The white wire is ckt 17 but where in the truck is that terminal connection?

Given the condition of wiring, specifically the back of the truck, I figured I'd wait two days for the new switch before trying to jump the terminals.
(Being only a few months experienced with this, I didn't have the confidence to jump them.)

In regards to the back of the truck.
I only have two bulbs in red covers that operate as my tail-lights, brake lights and blinkers. These are screwed into the frame that the hitch is welded to.
Why somebody once decided to strip the original brake/tail/blinker/reverse lights along with the housing for the bulbs behind the covers... is beyond me.
It's another project I have on my queue.

[bd]

Thank you.
Your help allowed me to see it in my wiring diagram.

The bottom of the fuse is the hot side, meaning it's getting it's power from behind the fuse panel through the firewall from a 12gauge wire in ckt2 into the bulkhead. Correct?   Correct.
If I'm to check this, it invites the question I've been putting off for now. How do I successfully remove my bulkhead connector and fuse panel? 
I've only be able to separate them about 2 inches from each other by removing the center screw in the bulkhead and the corner screws on my fuse panel.   The single bolt in the center of the bulkhead connector (engine compartment side) retains the engine compartment harness to the firewall mounted connector.  Backing out the bolt separates the engine compartment harness from the firewall socket.  My recollection is foggy regarding the attachment of the AGC fuse box and the bulkhead connector inside of the cab.  Post a couple of clear pics of the fuse box mounting inside the cab.

The white wire is ckt 17 but where in the truck is that terminal connection?   The turn signal connector is constructed from black or white plastic measuring roughly 6" x 2" x 1/4" (long and flat) and fastens to the side of the steering column under the dash.  Circuit 17 runs through that connector into the turn signal switch.

Given the condition of wiring, specifically the back of the truck, I figured I'd wait two days for the new switch before trying to jump the terminals.
(Being only a few months experienced with this, I didn't have the confidence to jump them.)   Honestly, possessing a new switch has no bearing on jumping orange Ckt 40 to white Ckt 17.  It is a good idea to make a fused jumper for your tool box - a couple of 12" long 14-gauge wires with alligator clips attached via ring terminals to a threaded stud-type 15- or 20-amp circuit breaker (image).  Insulate the threaded studs with rubber vacuum caps.  Easy peasy.

In regards to the back of the truck.
I only have two bulbs in red covers that operate as my tail-lights, brake lights and blinkers. These are screwed into the frame that the hitch is welded to.
Why somebody once decided to strip the original brake/tail/blinker/reverse lights along with the housing for the bulbs behind the covers... is beyond me.
It's another project I have on my queue.

[Spool]

Okay. I'm dealing with a rat's nest.

I was able to separate the bulkhead from the fuse panel with a bit of muscle.

In doing so, I unwrapped all the electrical tape and found my white wire coming from the brake switch which makes a very long unnecessary journey
to this terminal in my first photo attached, which is sitting under my steering column and in terrible shape.

When I located the terminal for ckt 17 (2nd photo attached), I found it was empty for any current possible connection.
This terminal is connected into the back of my gauge cluster.

Do you suppose I should attempt to reroute this white wire to the ckt terminal for 17?

[bd]

 



Pay attention to your wiring diagram!  Look at the annotations, below.  The white (Ckt 17) wire is exactly where it is supposed to be in the turn signal switch connector.  Does it measure 12 volts when you step on the brake pedal or jump orange to white at the brake switch? 

Cavity number "17" on the I/P cluster connector has absolutely nothing to do with the brake lamp circuit.  Don't confuse circuit numbers on the wiring diagram with the cavity numbers physically cast into the wire connectors in the vehicle.  There is NO CORRELATION between the two!

[Spool]

Thanks BD.
As always, I appreciate your time with your wiring diagram notes and also appreciate your patience with my learning curve.

In the morning, I will test the white wire terminal on ckt 17 at the turn signal switch.

May I ask what the jump between the two ckt's will do?
It appears I may have foolishly put this off for too long.

In doing so, I take it the engine must be on.
I'll separate the terminal connection slightly to be able to touch both terminals simultaneously with a paper clip?
In doing that, what should I expect?

(I acknowledge your fused jumper/20amp circuit breaker recommendation, but this too is entirely new to me and I feel partially guilty for inciting an electricity lesson in the thread)
However, I'll ask if you're willing to answer.
What is inside the circuit breaker and what is it's function?

Something like this?
https://www.amazon.com/Bussmann-BP-CBC-20HB-RP-Circuit-Lengthwise/dp/B004AHACW0/ref=pd_sim_263_2?_encoding=UTF8&pd_rd_i=B004AHACW0&pd_rd_r=ZHKJ6KWTZMPV40BQDEF5&pd_rd_w=WI0jc&pd_rd_wg=QkboW&psc=1&refRID=ZHKJ6KWTZMPV40BQDEF5


What does I/P stand for in I/P Cluster?
Is this the only place in the truck where I refer to terminals as cavities?

I did notice that my orange B+ feed to the brake switch is coming from a different point in the fuse panel than dictated from the wiring diagram you pointed out for me.
Is this normal? I've attached a photo.

I'd love to strip these wires/connections and make a clean contact on both points for the brake switch.

[bd]

Just install the new brake switch, make sure the turn signal switch is plugged in, and step on the brake pedal.  Do the brake lights work?  Yes or no. 

What is inside the circuit breaker and what is it's function?

Circuit protection in the form of a fuse or circuit breaker is a highly specialized, current-limiting switch.  When current flow through a circuit surpasses the current rating of its circuit protection, the circuit protection "blows," severing the circuit's connection to power.  When a fuse blows, the fuse fails destructively and must be replaced in order to restore power.  When a circuit breaker blows, it can be reset to restore power, avoiding replacement.  There are two types of automotive circuit breaker - manual reset and auto reset.  A "reset" button or lever must be operated in order to restore power through a manual breaker.  The auto reset breaker resets automatically after a brief time delay.  Auto reset breakers are generally preferred unless operator interaction is deemed necessary, such as when the breaker is protecting a motor circuit that could cause injury or property damage if it restarts spontaneously.

Circuit breakers generally consist of one flexible bi-metal contact and one fixed contact, together enclosed within an insulated housing.  The contacts touch by default.  Each contact connects to a discrete and separate terminal that is external to the housing.  A bi-metal is composed of two thermally dissimilar metals that are sandwiched together, but that expand at different rates as they heat or cool, causing the bi-metal to flex or bend.  The bi-metal is calibrated to a specific current threshold, beyond which the bi-metal heats sufficiently to cause it to flex away from the fixed contact, thereby opening the circuit.

What does I/P stand for in I/P Cluster?
Is this the only place in the truck where I refer to terminals as cavities?

I/P = instrument panel
Bookmark Common Automotive Acronyms.

cavity > noun  1. a hollow space within a solid object.
connector > noun  1. an insulated shroud that houses one or more terminals or terminal ends.
terminal > noun  1. a point of connection in an electric circuit.
terminal end > noun  1. a conductive device at the end of an electrical wire used to connect the wire to a terminal.

Within the context of your question, never refer to terminals as cavities.  They are not the same.  Cavities are the holes in connectors that may or may not be occupied by terminals and/or terminal ends.

I did notice that my orange B+ feed to the brake switch is coming from a different point in the fuse panel than dictated from the wiring diagram you pointed out for me.
Is this normal? I've attached a photo.

The brake switch B+ connection (Ckt 40) has been relocated to the adjacent "Battery" fuse, Ckt 140.  It is electrically the same, but curious as to why it was moved.  Another mystery hack.

[Spool]

Awesome!
Cavity. Terminal. Terminal End. Connector.
Never to confuse again.

I installed the new brake switch but haven't been able to get the brake lights to work or
a reading on the white wire other than .03v

I've been thinking about swapping the wires and terminal ends for a fresh start at this point; just to familiarize myself and take another step in restoring the truck.

However, I questioned jumping the ckt's again as you mentioned that replacing the switch has no effect on jumping the ckts?
What exactly would I be doing in jumping the ckt 17 from ckt40? What is the effect to ckt17?

[bd]

Given the condition of wiring, specifically the back of the truck, I figured I'd wait two days for the new switch before trying to jump the terminals.
(Being only a few months experienced with this, I didn't have the confidence to jump them.)   Honestly, possessing a new switch has no bearing on jumping orange Ckt 40 to white Ckt 17.  It is a good idea to make a fused jumper for your tool box - a couple of 12" long 14-gauge wires with alligator clips attached via ring terminals to a threaded stud-type 15- or 20-amp circuit breaker (image).  Insulate the threaded studs with rubber vacuum caps.  Easy peasy.

However, I questioned jumping the ckt's again as you mentioned that replacing the switch has no effect on jumping the ckts?
What exactly would I be doing in jumping the ckt 17 from ckt40? What is the effect to ckt17?

At the time I commented, the brake switch being the original part was irrelevant.  There was no reason to postpone the test until the new switch arrived.  Think of the turn signal switch as a traffic cop, directing power to the front and rear signal lamps to suit the circumstances.  The turn signal switch is actually an assemblage of several discrete switches that are organized into a front lamp control section and a rear lamp control section.  The brake lamp switch supplies brake lamp power (B+) to the rear lamp control section of the turn signal switch.  The turn signal switch, in turn, ( ) directs brake lamp power to left rear, right rear, or both rear lamps, depending on the position of the turn signal switch lever to select either right turn, left turn, or no turn.  In other words, if the "right" turn signal is selected while depressing the brake pedal, only the "left" brake lamp illuminates continuously while the right rear lamp flashes, and vice versa.  Jumping the orange and white wires was a way to bypass the original brake switch and eliminate it as an "unknown variable," feeding power directly into the turn switch.  Since you now have a new brake switch, that ship has sailed.  For future reference, jumping any switch is equivalent to closing its contacts.

I installed the new brake switch but haven't been able to get the brake lights to work or a reading on the white wire other than .03v

^^^ This, I want to pursue for a moment.  In a completely new unit of time, connect your test light directly across the posts of the battery.  This should indicate the "normal" brightness of the test light.  Next, clip your test light to a shiny bare ground under the dash and probe any B+ source in the fuse box to verify the test light is effectively grounded.  Perform and respond to each step in turn.  Probe the orange wire at the brake switch.  Is the test light 'normally' bright or dim?  Depress the brake pedal while continuing to probe the orange wire.  Does the test light remain normally bright or does it dim?  Probe the white wire at the brake switch and depress the brake pedal.  Does the test light illuminate and is it normally bright or dim?  Probe the white wire as it enters the turn signal switch connector alongside the steering column.  Depress the brake pedal.  Does the test light illuminate and is it normally bright or dim?

[Spool]

Excellent, I like it.
In a new unit of time, here we go.

-On the battery, I grounded the test light to the negative terminal while touching the positive terminal with the test light illuminating successfully.

-I grounded the test light to a clean bolt above my e-brake and proceeded to test the test light by successfully touching a few fuses within the fuse panel.

Here it got interesting... I probed ckt 40 going into the brake switch and it had what seemed to be the same luminescence of testing the fuses and battery terminals.
When I depressed the pedal the light went off, however, when I released the brake pedal, the light never came back on.
I never had a successful light test from ckt 17 on the brake switch.

I did however ground my multi-meter to the same clean bolt above my e-brake to read the voltage of ckt 40 going into the brake switch.
With the engine on, it read about 13.40 and then drops to zero when I depress the brake pedal.
I was still unable to get a reading from ckt 17.

Side question, does the engine have to be on when doing these test or is closing the ignition switch enough to do proper electrical testing?

Just to have a clean start, I currently did away with the brake switch connector and crimped spade connectors to the respective wires in question.
Previous owners had formed the habit of cutting just before the terminal ends when rewiring) I've attached photos.

[bd]

By definition, B+ is constant battery power; I+ is ignition power.  The brake lamp circuit is powered by B+, so ignition does not need to be on for these tests.

Your tests indicate there is excessive resistance in the B+ circuit feeding the brake switch.  That's why the voltage decreases toward zero when the circuit is loaded by depressing the brake pedal.  The brake switch is trying to power the rear lamps.  There simply is not enough voltage available to do it.  Are you tracking with this?  The problem isn't in the brake switch or the turn switch or the wiring running to the back of the vehicle.  The problem is somewhere between the battery positive connection and the brake switch.  Since you haven't mentioned anything else that isn't working properly, I surmise the problem is between SPLICE 2 and the fuse box.  Look at your schematic diagram.  Splice 2 is illustrated off of the top right corner of the fuse box, rear view.  In fact, splice 2 is taped up inside the dash harness in proximity to the fuse box.  If you've unwrapped the harness already, you should be able to locate it easily. 

To narrow your diagnosis, probe the lower socket connections of the three fuses acquiring power from the bus labeled B+ in the schematic diagram I posted earlier.  While probing the fuse sockets.  Does the test light illuminate normally bright or is it dim?  Depress the brake pedal and retest.  Is the test light normally bright or dim?  If the test light illuminates normally bright in both tests, probe the top of the three fuses in turn.  Depress the brake pedal.  What happens with the test light?  Remove all three fuses and thoroughly clean the fuse ends and fuse box sockets then retest.

Regarding the wire terminal ends, pick up a handful of Series 56 terminals from your local parts house, so you can reuse the factory connectors.  Be sure to crimp and solder any new terminals that you install.

[Spool]

Thank you.

You mentioned the brake lamp circuit is powered by the B+ not the I+, but just for my own understanding why is it that the brake lights do not illuminate when pressing the brake pedal (when they work) when the engine/ignition is turned off/open?

I tested all three fuses in question connected to the B+ power supplied on the rear side of the fuse panel.
All but one negative terminal on the top right of the front side illuminated. I've attached a photo circled in green.

I've taken them out and wiped them but no luck.

Perhaps the excessive resistance in the B+ circuit came from someone before me re-patching the B+ of the brake switch?
Maybe a better question would be, how do I wire it correctly as done by Chevy?
(Makes me wonder how long my brake lights have been out, I only thought to question it when I dropped an inline fuse to my junction box when repairing the starter)

I've attached a second photo of what SPLICE 2 may be (Again, terrible condition). 
It comes from the fuse panel but then I lose it's route as it goes into the corner of the firewall and frame of the truck on the drivers side.
I was unable to locate it on the engine side of the firewall.

I may be getting ahead of myself here, but do you happen to have a vendor recommendation?
Autozone didn't know what I mean't by female spade connector with a locking tab, nor did they carry them.
Also, my results of cleaning the fuse panel with a brush, air, and towel do not seem to be producing significant results with all the years of gook on it. (I suppose I could include my bulkhead connector on this as well)
Do you personally recommend a vendor that supplies spade connectors with locking tabs, series 56 connections or fuse panels and bulk head connectors?

[bd]

You mentioned the brake lamp circuit is powered by the B+ not the I+, but just for my own understanding why is it that the brake lights do not illuminate when pressing the brake pedal (when they work) when the engine/ignition is turned off/open?   The brake lights are fed via fused battery power.  You can confirm this by studying the wiring diagram.

I tested all three fuses in question connected to the B+ power supplied on the rear side of the fuse panel.
All but one negative terminal on the top right of the front side illuminated. I've attached a photo circled in green.   Replace the fuse!

I've taken them out and wiped them but no luck.   Sand the fuse sockets using a 320 grit (or so) emery cloth.  Or, use toothpaste (not tooth gel) and a Q-Tip.  Toothpaste contains a very fine abrasive.  Just rinse it off thoroughly with mouth wash before reassembly.      You could also use a generic aerosol electronic tuner cleaner or CRC QD Contact Cleaner or any combination of methods to achieve the needed results.  I once used carborundum valve lapping compound in a severe case of corrosion.  You need to be creative with what you have available.

Perhaps the excessive resistance in the B+ circuit came from someone before me re-patching the B+ of the brake switch?   I think you will discover that the problem is restricted to the fuse box connections and fuse.
Maybe a better question would be, how do I wire it correctly as done by Chevy?   Trace the orange Ckt 40 from the fuse box using your wiring diagram - it splices with 16-ga orange wires running to the brake lamp switch, the headlamp switch and the under dash courtesy lamp.  It is as yet undetermined why the circuit leg originally running to the brake lamp switch was abandoned in favor of the substitute red wire presently connecting to the BAT fuse in the fuse box.
(Makes me wonder how long my brake lights have been out, I only thought to question it when I dropped an inline fuse to my junction box when repairing the starter)

I've attached a second photo of what SPLICE 2 may be (Again, terrible condition).
It comes from the fuse panel but then I lose it's route as it goes into the corner of the firewall and frame of the truck on the drivers side.   Splice 2 is a spliced junction of roughly six 12-ga red wires.  The image you provided is of orange and white wires that are probably tied into the courtesy lamp circuit.
I was unable to locate it on the engine side of the firewall.   It disappears into the left kick panel behind the park brake pedal assembly.

I may be getting ahead of myself here, but do you happen to have a vendor recommendation?   We've been through this a few times in your other thread.  Bookmark What's everybody's favorite source for buying wiring/looms/etc.?.
Autozone didn't know what I mean't by female spade connector with a locking tab, nor did they carry them.   
Also, my results of cleaning the fuse panel with a brush, air, and towel do not seem to be producing significant results with all the years of gook on it. (I suppose I could include my bulkhead connector on this as well)   To remove the sticky sealant from the bulkhead connector, use aerosol carburetor cleaner or starting fluid.  But be careful.  Both are highly flammable and hazardous to breathe for any length of time.  Be sure to repack the bulkhead connector with antioxidant paste during reassembly.  Inside the cab, use Simple Green, 409, Windex, etc, with an old toothbrush.
Do you personally recommend a vendor that supplies spade connectors with locking tabs, series 56 connections or fuse panels and bulk head connectors?   For small quantities I use Del City.

Remove your ring and any other metal jewelry while working on any electrical system as a matter of safety.  If you inadvertently touch the ring between B+ and ground simultaneously, you could be branded for life or lose a finger.  The metal can superheat and melt like a fuse almost instantly.  It produces deep, incredibly painful burns that can be disfiguring.  It's better to avoid the risk.