Head light and taillights help

[69bronco69]

69 Ford bronco with upgrade headlight harness with relays installed a cpl years ago. I am running only stock head lights. New light switch was installed 5-6 years ago. I have recently developed this problem. When I turn on the lights, both of my low beams don't work and brake lights don't work. High beams, tail lights, turn signal lights all work properly.
I replaced the dimmer switch and issue is still present. I am about the replace the wire connector at the dimmer switch next. Before I start chasing all the possible rabbits, anyone have any idea what this is if the new connector doesn't solve the issue?

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[B RON CO]

Hi, do the brake lights work when the headlights are off? Check the brake light switch at the brake pedal for 12 volts in and out of the switch with a test light.
I would look at the relay for the low beam and see if the wire from the head light switch is hot at the relay. If it is hot, maybe the relay is bad. If the wire is not hot, follow it back to the dimmer switch, and find out where it loses power. Good luck

 

[garberz]

Sounds like the headlight switch is bad. The brake switch gets its power from the headlight switch. Pull the lead off the dimmer switch and check for 12v. on the low beam terminal. No voltage tells you your issue is the headlight switch or possibly somewhere between. If you have 12v. at the dimmer switch, then your issue is farther down stream. Have you verified that both low beams aren’t burned out? Don’t laugh!

Mark

 

[69bronco69]

Hi, do the brake lights work when the headlights are off? Check the brake light switch at the brake pedal for 12 volts in and out of the switch with a test light.
I would look at the relay for the low beam and see if the wire from the head light switch is hot at the relay. If it is hot, maybe the relay is bad. If the wire is not hot, follow it back to the dimmer switch, and find out where it loses power. Good luck

Brake lights do not work at all. I will check on other items tomorrow.

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[DirtDonk]

Could be one problem, or could be two.
High beams working tells you that your high-low switch on the floor is getting power when it should. But it's not telling you where it's going, so testing the switch and connector as suggested is a good first step.

Testing the headlamps themselves with an ohm-meter is a good second step. As mentioned, it's not impossible for them both to burn out.

Swapping relays is a good third step if the first two don't pan out.

Since the brake light power does come from the headlamps switch, it's not impossible for a bad connector at the switch to have an effect. Not common, but not impossible.
But I would check the brake light switch first. Verify that there is power coming in from one leg (Red) and going out the other (Red w/black) when you press the pedal.

The fact that your hazards and turn signals work means that all of your wiring from the firewall to the back lamps is fine. Anything with the brake lights is happening up under the dash.
Or, I suppose it's still possible for the brake light issue to be the turn signal switch. But this would be an unusual failure mode for one of those I think.
Likely a brake switch.

Good luck.

Paul

 

[69bronco69]

Could be one problem, or could be two.
High beams working tells you that your high-low switch on the floor is getting power when it should. But it's not telling you where it's going, so testing the switch and connector as suggested is a good first step.

Testing the headlamps themselves with an ohm-meter is a good second step. As mentioned, it's not impossible for them both to burn out.

Swapping relays is a good third step if the first two don't pan out.

Since the brake light power does come from the headlamps switch, it's not impossible for a bad connector at the switch to have an effect. Not common, but not impossible.
But I would check the brake light switch first. Verify that there is power coming in from one leg (Red) and going out the other (Red w/black) when you press the pedal.

The fact that your hazards and turn signals work means that all of your wiring from the firewall to the back lamps is fine. Anything with the brake lights is happening up under the dash.
Or, I suppose it's still possible for the brake light issue to be the turn signal switch. But this would be an unusual failure mode for one of those I think.
Likely a brake switch.

Good luck.

Paul

Using multimeter I tested the following: power at dimmer switch/connector and power at headlight connector. Both read 11.90 volts. Same reading when switch on low and high beams. Just to make sure I did this right, I set multimeter to 12v. Put red probe on middle pin/connector and black probe on frame to ground.
So possibly just headlights? Both? If so, then why no brake lights?

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[DirtDonk]

Using multimeter I tested the following: power at dimmer switch/connector and power at headlight connector.

When you say headlight connector, do you mean the old one that your new relays are attached to for their signal? If so, then you're good up to that point.
Did you check for both low and high right up to that connector? Sounds like it.
If so, then that's good and you're narrowing things down.

Both read 11.90 volts.

Is this with the engine off? What's the battery reading at that point? If 12.5v or less, your wiring is in surprisingly good shape for how old it is!
Of course, you'd rather see closer to battery voltage, but at about .5v loss, you're better off than many.

Just to make sure I did this right, I set multimeter to 12v. Put red probe on middle pin/connector and black probe on frame to ground.

Yep, sounds correct to me.
Then after that, you checked for power at the two other posts when in low and high? Sounds like you did because you mentioned getting readings in low and high at least up to the old headlight connector.
If so, then it could be your low-beam relay gone bad. Hence my recommendation for swapping the relays (by that I meant one for the other) to see if the problem follows the relay. If it's bad, then your high-beams would not work after the swap.

So possibly just headlights? Both? If so, then why no brake lights?

Because they don't necessarily have anything to do with one another. Remember the suggestion to check the brake light switch up under the dash? Look for power all the time at the Red wire, and power at the Red w/black wire when you depress the pedal.
Brake light switches are a very common failure point on these rigs. Not as often as the dimmer switch perhaps, but often enough that most long-term owners have had to replace theirs at least a time or three.
So check the brake switch. No need to wonder at why both front and back are out together yet. Wait until you exhaust all other possibilities with the tests outlined here.

At least checking the brake light switch is one of the easier under-dash tasks we have to go through. Most others involve twisting and kinking your spine to a much greater degree!

Paul

 

[69bronco69]

When you say headlight connector, do you mean the old one that your new relays are attached to for their signal? If so, then you're good up to that point.
Did you check for both low and high right up to that connector? Sounds like it.
If so, then that's good and you're narrowing things down.



Is this with the engine off? What's the battery reading at that point? If 12.5v or less, your wiring is in surprisingly good shape for how old it is!
Of course, you'd rather see closer to battery voltage, but at about .5v loss, you're better off than many.



Yep, sounds correct to me.
Then after that, you checked for power at the two other posts when in low and high? Sounds like you did because you mentioned getting readings in low and high at least up to the old headlight connector.
If so, then it could be your low-beam relay gone bad. Hence my recommendation for swapping the relays (by that I meant one for the other) to see if the problem follows the relay. If it's bad, then your high-beams would not work after the swap.



Because they don't necessarily have anything to do with one another. Remember the suggestion to check the brake light switch up under the dash? Look for power all the time at the Red wire, and power at the Red w/black wire when you depress the pedal.
Brake light switches are a very common failure point on these rigs. Not as often as the dimmer switch perhaps, but often enough that most long-term owners have had to replace theirs at least a time or three.
So check the brake switch. No need to wonder at why both front and back are out together yet. Wait until you exhaust all other possibilities with the tests outlined here.

At least checking the brake light switch is one of the easier under-dash tasks we have to go through. Most others involve twisting and kinking your spine to a much greater degree!

Paul

Motor was not running when I used multimeter. I put red probe on top post on back of headlight to get those readings. 11.90 on driver's side and 11.87 on passenger side. I also switched relays and it did not change the problem.

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[B RON CO]

Hi, if you are getting 12 volts at the headlight it should turn on, unless the bulb is bad. The ground must be ok or else the high beams would not work. You just traced the whole circuit and found power the whole way to the bulb. Now how about power in and out of the brake light switch.
You should get a $10 test light. You just clip it to a clean ground and test for current, one hand. I have a set of test leads for my multi meter with alligator clips so I only have to poke around with the red lead. Good luck

 

[69bronco69]

Hi, if you are getting 12 volts at the headlight it should turn on, unless the bulb is bad. The ground must be ok or else the high beams would not work. You just traced the whole circuit and found power the whole way to the bulb. Now how about power in and out of the brake light switch.
You should get a $10 test light. You just clip it to a clean ground and test for current, one hand. I have a set of test leads for my multi meter with alligator clips so I only have to poke around with the red lead. Good luck

I've tested brake light switch. Has 11.95v at back of connector. Also placed probe on post of brake switch between the connector. Still had 11.95v with brake pedal depressed and not depressed. Not sure I tested brake switch properly. Was it?

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[B RON CO]

Hi, I'm not really sure what you did. One wire (going in) should be hot all the time. The other wire should be hot only when you press the brake pedal.
If the " other wire" is hot when you press the brake pedal you need to remove the taillight bulb and check the socket. You may have bad bulbs.
There are two little wire leads in the socket, and the socket is the ground. One lead is hot when the brakes are on, and flashes for the directional and 4 way flasher. The other one is the running light, and should be hot when the headlight switch is pulled on.
Good luck

 

[69bronco69]

Hi, I'm not really sure what you did. One wire (going in) should be hot all the time. The other wire should be hot only when you press the brake pedal.
If the " other wire" is hot when you press the brake pedal you need to remove the taillight bulb and check the socket. You may have bad bulbs.
There are two little wire leads in the socket, and the socket is the ground. One lead is hot when the brakes are on, and flashes for the directional and 4 way flasher. The other one is the running light, and should be hot when the headlight switch is pulled on.
Good luck

After rereading dirt donk's reply, I went to recheck the difference between the constant hot (red) wire and the hot only when brake pressed (red w/black stripe) wire. While unplugging it, the red/black wire broke off at the terminal. So I guess I'll be buying new wire connector and retest. I may just buy new wire connector and brake switch while I'm at it.

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[69bronco69]

Motor was not running when I used multimeter. I put red probe on top post on back of headlight to get those readings. 11.90 on driver's side and 11.87 on passenger side. I also switched relays and it did not change the problem.

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I did have power with red wire on connector at brake switch. I ultimately broke the red w/black wire from the terminal on the connector. Guess I will order a new connector and new switch while I'm at it to make it worth the shipping.
I planned to upgrade to H4 lights anyway. Would you suggest new headlights since there was power on the rear posts on both headlights that only produced high beam light?

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[B RON CO]

Hi, it seams the headlight bulb is bad if it is getting power but not going on. You could remove it and connect it to a battery for a quick test.
You could test the brake lights by touching the two wires that go to switch together and see if the brakes light up. That will bypass the switch. Good luck

 

[DirtDonk]

I've always "upgraded" my headlights on old vehicles to H4's. But that's not the only solution. There are some pretty decent regular halogen sealed beams these days too.
My reasoning for swapping was to be able to choose my beam pattern, my wattage, and mostly to have a little safety and cost factor thrown in.
Safety factor is that when a rock breaks the lens on a sealed beam, the bulb is dead. In an H4 housing only the lens is broken, but the bulb still functions.
And cost is (or at least used to be) less for just a replacement bulb than it used to be for a full lamp unit.

If you're happy with your lights, there's no reason to change (other than to fix blown low-beams that is!) style/type. However, if you've never been impressed, there's a lot out there.

Paul

 

[69bronco69]

Hi, it seams the headlight bulb is bad if it is getting power but not going on. You could remove it and connect it to a battery for a quick test.
You could test the brake lights by touching the two wires that go to switch together and see if the brakes light up. That will bypass the switch. Good luck

I touched brake switch wires together and the brake lights worked. So I guess I'm buying brake switch, brake switch connector, and two H4 headlights

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[B RON CO]

Hi pretty normal, more than one problem.
You can use your meter and test the switch for continuity, as a learning experience. Hook it up and give it a squeeze.
You can also test the headlight bulbs with some jumper leads. From the back of the bulb the left prong is ground, top is low beam and right is high beams.
I show my son how to test everything. No one else is going to show him.
Good luck

 

[69bronco69]

Update:
Replaced headlights with H4's. Both low beams and hi beams work.

Replaced wiring connector to brake switch and now have functioning tail lights and brake lights.

That wiring is getting old. Most is original.

Thanks to all who helped

 

[DirtDonk]

Great work. Thanks for the follow-up.

Paul