No brake lights, pretty frustrated at this point

[chillman88]

Ok guys,

I just put some LED taillight bulbs in (Sylvania from Walmart) and my brake lights are not working. I don't know if it's wiring or an issue with the bulbs. I tried the old bulbs and they aren't working either but they could be blown.

HAZARDS AND SIGNALS WORK

So... Where do I start? Check the brake switch and go from there? I thought the brake signal used the same wires as the turn signals.

These are the kinds of things that I usually overlook something simple so please give me a poke in the right direction.

 

[saburai]

Do you have a multimeter? If not, go get one.

 

[Kevin 007]

Try replacing the hazard flasher. On the pre 87 models the brake lights and hazards share a circuit somehow. Don't ask me how but there is some relation there. So its worth a try, also check your fuse of course and check the hazard switch also.

 

[dgr]

We had a similar issue with our late 70s f350. Single bulb taillights, the brake lights run through the turn signal switch. We pulled the steering wheel and twisted the eyelets in the rivets and they started working again.

 

[Selahdoor]

Did you pull them, flip them over, and try again?

 

[chillman88]

Do you have a multimeter? If not, go get one.

Of course I do. Just haven't started looking at it and I'm extremely frustrated with it right now. Needed to vent a little bit and give myself a chance to calm down.

Try replacing the hazard flasher. On the pre 87 models the brake lights and hazards share a circuit somehow. Don't ask me how but there is some relation there. So its worth a try, also check your fuse of course and check the hazard switch also.

Hazard flasher is only a couple of years old, hazards work fine?

We had a similar issue with our late 70s f350. Single bulb taillights, the brake lights run through the turn signal switch. We pulled the steering wheel and twisted the eyelets in the rivets and they started working again.

Turn signals work fine too, that's why I'm so frustrated.

I'm going to start with the fuse and the brake switch. Fuse should be good because it powers something else that works, don't remember what right now.

Did you pull them, flip them over, and try again?

At first they didn't light up at all. Flipped them over and now they work for running lights and signals.

 

[gandalf]

As I recall the hazards and the turn signals use the same "brighter" filament of the bulb as the brake light. If I'm correct is thinking that, then I'd say perhaps the brake light isn't being told to light up. That being the case, I'd look at the brake switch. I think it's somewhere down around the brake pedal.

Keep in mind I'm going completely from memory on this, and my memory has been known to be faulty.

 

[chillman88]

Also noticed that the led lights up very dimly as soon as the ignition is turned to run. Not bright, but must be some parasitic crossover somewhere.

 

[saburai]

Sorry friend
didn't mean to come off like a ****. Just remembered that you said I should bring my multimeter

 

[chillman88]

Sorry friend
didn't mean to come off like a ****. Just remembered that you said I should bring my multimeter

Nope that's fine. I just have a "horrible freight" multimeter so I don't TRUST it. Ask @Selahdoor about the quality of those

 

[dgr]

Yes. The turn signals worked fine on our truck too. Brakes didn't.

Power for the brake lights comes through the brake light switch on one wire to the turn signal switch. Always hot.

Power for the turn signals comes on a separate with through the flasher. Hot in run only.

When you turn the switch left or right, it switches the feed from the always hot to the hot in run.

This is how American cars can use the same filament for the turn and brakes

Good idea to check the brake switch. It would also be a good idea to put a known good bulb in there.

This image might help. You can see all the magic where it says Right Turn in the middle

You must be registered for see images attach

 

[Selahdoor]

Nope that's fine. I just have a "horrible freight" multimeter so I don't TRUST it. Ask @Selahdoor about the quality of those

Made by politicians out of the finest chinesium.

I tested my friend's meter, against both the new flukes, and against the HF, and my old analog,

Everything tested exactly the same. Except the HF. It was off by a few volts.

Man, it was nice, after that, to get out the fluke the next time I needed a meter... and I KNEW the results were right on.

Yes. The turn signals worked fine on our truck too. Brakes didn't.

Power for the brake lights comes through the brake light switch on one wire to the turn signal switch. Always hot.

Power for the turn signals comes on a separate with through the flasher. Hot in run only.

When you turn the switch left or right, it switches the feed from the always hot to the hot in run.

This is how American cars can use the same filament for the turn and brakes

Good idea to check the brake switch. It would also be a good idea to put a known good bulb in there.

This image might help. You can see all the magic where it says Right Turn in the middle

You must be registered for see images attach

If the turn signal works, the bulb is good for the brakes. It's just not getting the brake signal.

Yes, I'd start with the brake switch.

Even a politician of an HF meter, will tell you whether you have voltage or not...

 

[gandalf]

Nope that's fine. I just have a "horrible freight" multimeter so I don't TRUST it. Ask @Selahdoor about the quality of those

Yep, I have one of those too. Those are the reason we invented the term "POS".

I've since replaced it with a somewhat better POS from Frys.

 

[chillman88]

Yes. The turn signals worked fine on our truck too. Brakes didn't.

Power for the brake lights comes through the brake light switch on one wire to the turn signal switch. Always hot.

Power for the turn signals comes on a separate with through the flasher. Hot in run only.

When you turn the switch left or right, it switches the feed from the always hot to the hot in run.

This is how American cars can use the same filament for the turn and brakes

Good idea to check the brake switch. It would also be a good idea to put a known good bulb in there.

This image might help. You can see all the magic where it says Right Turn in the middle

You must be registered for see images attach

THANK YOU!

This is exactly what I was hoping for! Really appreciate it, it will help a lot!

EDIT: Looks like according to that diagram, given everything else works, it's most likely something to do with the switch on the pedal. Hazards work and they're on the same fuse. Has to be somewhere between the fuse and the turn signal switch because everything else works.

 

[chillman88]

Made out of the finest chinesium politicians.

Fixed it for you bud