Brake lights not working

db

None of the brake lights on my Hyundai Montana are working. I have replaced the fuse and tested the switch on the pedal and the wiring harness and all are working.

Any ideas what else I could try? I noticed on another thread about a similar problem that it was a different fuse than on the fusebox layout so I will try that tomorrow.

jca

Both bulbs aren't blown by any chance?

db

As far as I can tell the brake light is in the same bulb as the tail light. I checked the bulbs and the filament is intact. The top brake light is also not working so I doubt they would all fail at the same time.

jca

If you can locate the brake light switch, disconnect the 2 wires connected to it and join them together. If that gives you light it's a faulty switch.

db

I've tested both the switch and the harness and both appear to be OK. The switch is closed when the pedal is pressed and open when released. The harness has 12V through the same 2 pins.

allthedoyles

You need to rule out the bulbs first

boardsuser1

It is possible for the tail light to work and the brake light won't had this issue many times even if both are working from 1 bulb.

db

All three brake lights are not working so very unlikely they all failed at the same time. I will replace one anyway just to be sure. If it's not the bulbs, switch or fuse what else might be wrong?

allthedoyles

You could get a mechanic to run a diagnostic check

boardsuser1

Take it to an auto sparks if that doesn't work.

jca

db wrote: »

I've tested both the switch and the harness and both appear to be OK. The switch is closed when the pedal is pressed and open when released. The harness has 12V through the same 2 pins.

Is there power at the switch harness?

db

jca wrote: »

Is there power at the switch harness?

Yes, there is 12V and when I pull the fuse it is 0 so that rules out the fuse. I have tried a new switch but still not working.

pablo128

Have you tried a new bulb yet? Or at least see if there's power going to the bulb holders?

colm_mcm

Check the earthing, but I would have thought this would affect other lights too.

db

Tested the bulbs and they're fine. No power to the bulb holder when the brake pedal is pressed. The brake light and tail light are in the same bulb with a common ground so I can't see it being an earthing problem.

Everything points to the switch but I tested it and it's working fine. I even tried with another switch.

Esel

Sounds like wiring then?

colm_mcm

Can you check continuity?

db

colm_mcm wrote: »

Can you check continuity?

Do you mean from the switch harness to the light bulb holder? The problem seems to be somewhere between the two but it would be difficult to check continuity between them. Should there be continuity between the harness and ground?

db

I checked the socket on my towbar and all the lights are getting power except the brake light. I think I have to admit defeat on this one.

colm_mcm

Check where the towbar is wired in to the loom.

jca

A pound to a penny says there's a broken wire where the tow hitch wiring is spliced into the vehicle harness. I never thought of the dreaded ball hitch. I hate them, any car I owned that had one was quickly relieved of it.

jca

db wrote: »

I checked the socket on my towbar and all the lights are getting power except the brake light. I think I have to admit defeat on this one.

Don't give up. Just follow logic, it's only electric current running along a wire, it'll be something simple in the end.

db

So I opened up where the towbar wiring is spliced in and the join is perfect with the towbar brake wire soldered onto the car brake wire just before the harness into the light cluster. It has been working with the towbar since I got it fitted six months ago so it is wired correctly.

jca

db wrote: »

So I opened up where the towbar wiring is spliced in and the join is perfect with the towbar brake wire soldered onto the car brake wire just before the harness into the light cluster. It has been working with the towbar since I got it fitted six months ago so it is wired correctly.

OK. Is there power there? Pedal pressed obviously. Going back to the switch, is power going from one side to the other when the pedal is pressed?

db

To summarise

Switch - Open when button is pressed, ie brake off, closed when button is released. Also replaced with new switch.
Switch Harness - 12V through same pins as operated by the switch.
Fuse - Switched with another fuse and working correctly. No power at switch harness when fuse is removed.
Light Cluster - Power at harness for all lights except brake light (brake pedal pressed).

The fault must be somewhere between the switch harness and the light cluster but the wiring is mostly hidden.

Greyfoot

How you checked power at the light cluster harness? If you 100% sure you identified it correctly and not getting power on it but all else check out you have broken/shorted wiring.