Brake lights . Help

[englands 71]

Guys My 71 has no Brake lights .
I put in a new turn signal switch a few months ago . I noticed that the brake lights were not working a few weeks later. So I put another turn signal switch in and still no brake lights . If I turn the left turn signal on I have a right brake light when I mash the pedal. I have headlights , tail lights and have flashers only in front . Changed bulbs and checked fuses , tried another brake light switch .
Any suggestions? Thanks ahead of time.

[VetteVet]

Originally Posted by englands 71

Guys My 71 has no Brake lights .
I put in a new turn signal switch a few months ago . I noticed that the brake lights were not working a few weeks later. So I put another turn signal switch in and still no brake lights . If I turn the left turn signal on I have a right brake light when I mash the pedal. I have headlights , tail lights and have flashers only in front . Changed bulbs and checked fuses , tried another brake light switch .
Any suggestions? Thanks ahead of time.

These symptoms almost always turn out to be caused by poor grounds.
clean all the sockets where the bulbs go in and where the sockets mount to the bed. Make sure you have a good ground from the bed to the frame and from the frame to the negative battery terminal.

Unplug your steering column plug and look at the half that comes from the fuse panel and the cab firewall.

The white wire is the brake switch wire. It is hot when you push on the pedal.

jumper between the white wire and the yellow wire which is the left turn/ left brake light.

Push on the pedal and the left brake/turn light should come on.

do the same for the dark green wire which is the right turn/brake light wire.

If the lights don't come on then either:

There is a break in the wires to both lights.
They are not grounded.
Or the bulbs are blown.

If you can get to the connector at the rear of the truck, pull it apart and check for 12 volts on those two wires when a helper pushes the brake pedal.

If you have a multimeter and you know how to use it you should get 12 volts between the wires and the frame. Since your lights were working, you should get the 12 volts.

Now put the meter on Ohms to check resistance and check the other side of the connector that goes to the rear lights. If you know that your bulbs are good you should read resistance between the two brake/ turn wires and ground (frame) about 75 ohms if I recall correctly.

The tail lights are part of the bulb filament so if you have tail lights then you must be getting ground from the bulbs. In your post did you say you had tail lights or just front parking lights?

Try these checks and get back with the results.

[englands 71]

Originally Posted by VetteVet

These symptoms almost always turn out to be caused by poor grounds.
clean all the sockets where the bulbs go in and where the sockets mount to the bed. Make sure you have a good ground from the bed to the frame and from the frame to the negative battery terminal.

Unplug your steering column plug and look at the half that comes from the fuse panel and the cab firewall.

The white wire is the brake switch wire. It is hot when you push on the pedal.

jumper between the white wire and the yellow wire which is the left turn/ left brake light.

Push on the pedal and the left brake/turn light should come on.

do the same for the dark green wire which is the right turn/brake light wire.

If the lights don't come on then either:

There is a break in the wires to both lights.
They are not grounded.
Or the bulbs are blown.

If you can get to the connector at the rear of the truck, pull it apart and check for 12 volts on those two wires when a helper pushes the brake pedal.

If you have a multimeter and you know how to use it you should get 12 volts between the wires and the frame. Since your lights were working, you should get the 12 volts.

Now put the meter on Ohms to check resistance and check the other side of the connector that goes to the rear lights. If you know that your bulbs are good you should read resistance between the two brake/ turn wires and ground (frame) about 75 ohms if I recall correctly.

The tail lights are part of the bulb filament so if you have tail lights then you must be getting ground from the bulbs. In your post did you say you had tail lights or just front parking lights?

Try these checks and get back with the results.

I've got tail lights but when I turn on the hazard lights I only have front hazards. The rear lights don't flash with hazards on.

Ok I'll give'er a try . Thanks Vette !

[englands 71]

I jumped the white wire to the green and yellow and the brake lights worked but when I hooked my meter onto the harness at the back of the bed I didn't get any power coming from it? I unplugged the brake switch and jump the orange wire to the white wire and no brake lights either .

[englands 71]

Originally Posted by VetteVet

These symptoms almost always turn out to be caused by poor grounds.
clean all the sockets where the bulbs go in and where the sockets mount to the bed. Make sure you have a good ground from the bed to the frame and from the frame to the negative battery terminal.

Unplug your steering column plug and look at the half that comes from the fuse panel and the cab firewall.

The white wire is the brake switch wire. It is hot when you push on the pedal.

jumper between the white wire and the yellow wire which is the left turn/ left brake light.

Push on the pedal and the left brake/turn light should come on.

do the same for the dark green wire which is the right turn/brake light wire.

If the lights don't come on then either:

There is a break in the wires to both lights.
They are not grounded.
Or the bulbs are blown.

If you can get to the connector at the rear of the truck, pull it apart and check for 12 volts on those two wires when a helper pushes the brake pedal.

If you have a multimeter and you know how to use it you should get 12 volts between the wires and the frame. Since your lights were working, you should get the 12 volts.

Now put the meter on Ohms to check resistance and check the other side of the connector that goes to the rear lights. If you know that your bulbs are good you should read resistance between the two brake/ turn wires and ground (frame) about 75 ohms if I recall correctly.

The tail lights are part of the bulb filament so if you have tail lights then you must be getting ground from the bulbs. In your post did you say you had tail lights or just front parking lights?

Try these checks and get back with the results.

Could I have yet another bad turn signal switch ?

[VetteVet]

Originally Posted by englands 71

Could I have yet another bad turn signal switch ?

take the steering column harness and check the white wire with the yellow for continuity with the lever in neutral. zero ohms.
put the lever in left turn check for infinity ohms, no reading.

now do the white and dark green, check for zero ohms with the lever in neutral.
Put the lever in right turn and check for infinity or no reading.

Check the purple wire from the fuse panel in the plug for 12 volts with the key on. (turn signal flasher power)

Check the brown wire for 12 volts with the key on or off.
(Hazard flasher)

Plug the harnesses back together if you get those readings and turn on the hazard flasher switch. Locate the connector in the firewall behind the distributor and see if you can unplug it. If you can then check the Y DK Green wires for 12 volts. If you get it then plug the connector back together and follow the harness down the firewall and along the left frame rail and look for a break in the wires or another connector and check the two wires in the connector for 12 volts. Then continue down the frame rail to the rear connector and recheck the two wires for 12 volts.

You said you didn't get any power before so if you don't get it now then you have a bad harness, You should have found the break in the wires on the previous checks by this time and you don't need to leave the hazard switch on all the time just turn it on when you check the wires.

[englands 71]

[QUOTE=VetteVet;8035431]take the steering column harness and check the white wire with the yellow for continuity with the lever in neutral. zero ohms.
put the lever in left turn check for infinity ohms, no reading.

now do the white and dark green, check for zero ohms with the lever in neutral.
Put the lever in right turn and check for infinity or no reading.

Check the purple wire from the fuse panel in the plug for 12 volts with the key on. (turn signal flasher power)

Check the brown wire for 12 volts with the key on or off.
(Hazard flasher)

Plug the harnesses back together if you get those readings and turn on the hazard flasher switch. Locate the connector in the firewall behind the distributor and see if you can unplug it. If you can then check the Y DK Green wires for 12 volts. If you get it then plug the connector back together and follow the harness down the firewall and along the left frame rail and look for a break in the wires or another connector and check the two wires in the connector for 12 volts. Then continue down the frame rail to the rear connector and recheck the two wires for 12 volts.

You said you didn't get any power before so if you don't get it now then you have a bad harness, You should have found the break in the wires on the previous checks by this time and you don't need to leave the hazard switch on all the time just turn it on when you check the wires.[/QUOTE

If I have brakes lights when I jump the white wire to the green and yellow wire under the dash that would mean my harness to the rear is good wouldn't it ? How else would it get power back there ?

I also jumped the hot white wire to the Orange and white wire that plugs into the brake switch and got nothing. Would that mean that the Orange and white connector is bad ? I looped the wire so that it touched the white and Orange wire from the hot white wire . No lights .

[englands 71]

I'll check the other stuff that you said to check . to be sure it's not another bad TS switch

[englands 71]

If I have brakes lights when I jump the white wire to the green and yellow wire under the dash that would mean my harness to the rear is good wouldn't it ? How else would it get power back there ?

I also jumped the hot white wire to the Orange and white wire that plugs into the brake switch and got nothing. Would that mean that the Orange and white connector is bad ? I looped the wire so that it touched the white and Orange wire from the hot white wire . No lights .

[VetteVet]

..............

Originally Posted by englands 71

If I have brakes lights when I jump the white wire to the green and yellow wire under the dash that would mean my harness to the rear is good wouldn't it ? How else would it get power back there ?

Yes that is what the brake switch does, when you press the pedal it closes the brake switch and the orange and white wire connects with the white wire, and sends power through the turn signal switch to the yellow and dark green wires to the rear brake lights. I thought I read that you didn't have power back there.

I also jumped the hot white wire to the Orange and white wire that plugs into the brake switch and got nothing. Would that mean that the Orange and white connector is bad ? I looped the wire so that it touched the white and Orange wire from the hot white wire . No lights .

You said that backwards. The orange and white wire is hot and the white wire isn't hot until the brake switch is closed by pressing the brake pedal, then the white wire is hot. So you are saying that when you jumped the brake switch, orange/white wire to white wire you got nothing? You could have a bad brake switch or the Stop/tail fuse is blown or not making a good connection in the fuse holder, which is pretty common. The fuse holders get corroded and need to be cleaned. The orange/white should be hot with the key off if the fuse is good.

[englands 71]

Originally Posted by VetteVet

..............

I meant I wasn't getting any reading on my meter at the harness at the back of the bed. But when I jumped the white wire to to the green and yellow under the dash I got brake lights.

I spliced into the Orange and white wire and jumped to the white wire in the harness and got nothing . Maybe it is the brake switch after all. The switch I tried was out of an old 55 Chevy that I'm building. It could be bad as well. Weirder things have happened.

I figured if I jumped the white wire to the yellow and green and mashed the brake pedal my switch was good if the brake lights worked .

[VetteVet]

Originally Posted by englands 71

I meant I wasn't getting any reading on my meter at the harness at the back of the bed. But when I jumped the white wire to to the green and yellow under the dash I got brake lights.

I spliced into the Orange and white wire and jumped to the white wire in the harness and got nothing . Maybe it is the brake switch after all. The switch I tried was out of an old 55 Chevy that I'm building. It could be bad as well. Weirder things have happened.

I figured if I jumped the white wire to the yellow and green and mashed the brake pedal my switch was good if the brake lights worked .

That would be the case if the orange wire going to the brake switch has power and the brake switch was good. Are you sure that the white wire from the brake switch is good all the way to the steering column plug?

[englands 71]

Originally Posted by VetteVet

That would be the case if the orange wire going to the brake switch has power and the brake switch was good. Are you sure that the white wire from the brake switch is good all the way to the steering column plug?

That I'm not sure of . How do it test it ? You may have already told me. I'm going crazy 😜

[VetteVet]

This can be confusing especially if you jump around too much. Your meter is your best tool to check for voltage or continuity on a wire.
From what you said earlier about jumping the white wire to the green and yellow wires and getting brake lights when you pressed the pedal, you must have power on the white wire when the brake pedal is pressed.

If you put the red lead of the meter on the white wire and the black lead on a good ground. You should get 12 volts when you press the brake pedal. If you jump the white wire to the other side of the steering column connector to the white wire there, you can check the dark green and yellow wires for 12 volts when you press the brake pedal.You have to have the signal lever in the neutral position. If you get the 12 volts on both wires then your turn signal switch is ok and the problem is further down the line toward the rear of the truck.

If you think you're confused, I'm working with three other guys with similar problems. LOL.

Do your checks and read all the posts and you'll get it fixed. Let me know what readings you get on the wires and I'll let you know if they are correct.

[englands 71]

Originally Posted by VetteVet

This can be confusing especially if you jump around too much. Your meter is your best tool to check for voltage or continuity on a wire.
From what you said earlier about jumping the white wire to the green and yellow wires and getting brake lights when you pressed the pedal, you must have power on the white wire when the brake pedal is pressed.

If you put the red lead of the meter on the white wire and the black lead on a good ground. You should get 12 volts when you press the brake pedal. If you jump the white wire to the other side of the steering column connector to the white wire there, you can check the dark green and yellow wires for 12 volts when you press the brake pedal.You have to have the signal lever in the neutral position. If you get the 12 volts on both wires then your turn signal switch is ok and the problem is further down the line toward the rear of the truck.

If you think you're confused, I'm working with three other guys with similar problems. LOL.

Do your checks and read all the posts and you'll get it fixed. Let me know what readings you get on the wires and I'll let you know if they are correct.

Ok Vette - will do . I really do appreciate this and at the same time i'm learning something as well.

[englands 71]

If you jump the white wire to the other side of the steering column connector to the white wire there, you can check the dark green and yellow wires for 12 volts when you press the brake pedal.

☝️

Vette not sure I understand what you mean. You mean jumping the white wire with the turn signal switch still connected ? Splicing into the yellow and green on the switch side .

[VetteVet]

Originally Posted by englands 71

If you jump the white wire to the other side of the steering column connector to the white wire there, you can check the dark green and yellow wires for 12 volts when you press the brake pedal.

☝️

Vette not sure I understand what you mean. You mean jumping the white wire with the turn signal switch still connected ? Splicing into the yellow and green on the switch side .

This is a check to see if the brake wires are getting power through the turn signal switch. I'll be a little more detailed.

First off make sure you have 12 volts on the wire wire coming from the brake switch when you press the brake pedal.

Disconnect the steering column connector plug.
Jump from the white wire that has power to the white wire that goes to the turn signal switch.

press the brake pedal.

Check the yellow and dark green wires in the steering column plug for 12 volts when you press the brake pedal.

Alternate check.

I think you have done this already but if not.

Jump the white wire with 12 volts on it from the brake switch to the yellow and dark green wires in the steering column that goes up into the firewall to the rear lights. Press the brake pedal and you should get the left or right brake light depending on which wire you have the white wire connected to.

This covers the complete brake light circuit, so one or the other tests is going to fail.

[englands 71]

Ok Vette this is what I found. I disconnected the harness, jumped the white wire from the truck harness to the yellow and green in the signal switch and got nothing.
I jumped the white wire to my harness and have brake light on green and yellow.

I've got 12 volts coming from the brake light switch with white wire jumped to it so that tells me the signal switch is no good.
Considering this will be the second new switch that I will put in , is there something I could be doing to the switch when I'm putting it in to make it fail ?

[englands 71]

Vette thanks a lot for your patience. That last test definitely proved it was the turn signal switch. I took it out and held it in my hand and my brakes worked. It appears that the switch was in some kind of bind and the harness had to be laying just right behind the steering wheel or it would short out. Weirdest thing I've ever seen , well maybe not the weirdest but anyway I got brakes now ! Thanks man !

[VetteVet]

Originally Posted by englands 71

Vette thanks a lot for your patience. That last test definitely proved it was the turn signal switch. I took it out and held it in my hand and my brakes worked. It appears that the switch was in some kind of bind and the harness had to be laying just right behind the steering wheel or it would short out. Weirdest thing I've ever seen , well maybe not the weirdest but anyway I got brakes now ! Thanks man !

Well good for you on fixing a tough problem. These switches are usually pretty reliable and simple to install. I would guess you just got a couple of bad ones.

I just saw this on the 67 to 72 board and thought of your thread.

http://67-72chevytrucks.com/vboard/s...d.php?t=711090