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Len69Coupe

Dash/Head Light issue

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Started to reassemble my dash after it being out for several years. Before reinstalling, I decided to replace the gauge circuit board, voltage regulator and install LED lights in the dash. Hooked everything back up and the LED's were nice and bright, but they were randomly shutting off for half a second and coming back on. I turned on the headlights and they would flicker at the same time as the dash lights.. I reinstalled the regular bulbs and couldn't see any light from them and the clicking also continued with flickering headlights.

After some research I found that the clicking was coming from the headlight switch. I had another headlight switch, so I installed it and it is also clicking and making the headlights flicker with no light from the dash lights. Even if I disconnect the dash connector the headlights still flicker and the switch clicks. So, it's not the dash circuit.

I have no taillights as well. Brake lights and turn signals work great (LED Sequential taillights).  I had no brake lights/taillights before I started on the dash. I troubleshot that to a bad brake light switch, and it fixed the brake lights, but still no taillights. Not sure if all this is related somehow.

What would cause the clicking from the switch and the lights to flicker?

 

 

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Yes it sounds like a short, perhaps somewhere in the headlight circuit. The circuit breakers in the light switch are auto-reset. When they cool down they turn on again. See how it reacts with high beams on. Also, I have heard of the dimmer switch wires shorting to the floor. I believe there is supposed to be an insulator under it. Below is part of the schematic, which is down in the "How To's" section. There is also the 30+ page Ford wire diagram down there if you need it. Schematics simplify the circuit and show you how it works, while wire diagrams show you how the car is actually wired with all the plugs, wire colors, etc. This is for Exterior lights. There is another page for the interior lights. Everything above the red line is the headlight circuit. If that doesn't do it, start disconnecting wires one at a time until it stops, then you'll have to follow that wire until you find the short. Since your tail lights don't work either, that involves both circuit breakers, and they should trip independently. It could be that it's such a solid short that it drags the voltage down coming into the light switch terminal B before the breaker trips. You need to find this thing before it melts some wires. I believe there are over 40 light bulbs on our cars, so this could take some digging. If you get stumped, tell us what you did and all the details- everything is a symptom. image.thumb.png.688a61f2a4942b899b5acaeab5e0c3d8.png

 

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Thanks guys. I had no idea there was a CB in that switch.  Makes sense now that I realize that.

Great explanation Mach1 driver. Going to be a few days before I can get back out there to work on it. I'll check back in.

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3 minutes ago, Len69Coupe said:

I have stock headlights. Those are Halogen right?

No, the stock headlights are incandescent, not halogen. They are called halogen because halogen gas is used, they glow brighter and use more amperage per watt than standard headlights. They give more light but since they use more power, they put stress on the 50+ year old electrical system.

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Do you have the flickering problem with the light switch in the first detent, known as the park position? If so this would eliminate the headlights and change the search criteria (unless you have multiple shorts).

I also recommend pulling fuse #5, its a 4 amp fuse that controls all these lights: ash tray, heater, radio, 2 clock and 8 dash instrument lights. 

image.png.a9f0b6064f5229347afbf3a6c081fa62.png

Then pull the light switch to the first detent (park) and see if any of these lights flash: front park lights, tail, side markers and license lamps. Then pull the switch all the way out and turn on the headlights and see if they cause the flashing.

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Yes, the lights flicker in detent one and flicker when pulled all the way out. I'll pull #5 fuse and see if there is a difference.

If no difference, I'll disconnect the high beam floor switch and see what happens. 

I keep thinking it must be related to the rear parking lights not working. 

Thanks.

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Here's the latest on the flickering dash and headlights. This flickering dash lights occur on the 1st detent. All dash and headlights (low and high) flicker when pulled all the way out. After market voltmeter drops to 8 -10 volts every time lights flicker.

I disconnected fuse #5 with no change.

I removed the dimmer switch with no change.

I have disconnected every headlight, even all at once, with no change.

I disconnected all marker lights, brake lights and dome light with no change.

I got to thinking about the Halogen headlights and I do have them. I've never changed any of the headlights, so I wasn't sure until I looked at the lights close. Shouldn't matter though since they're all disconnected.

I have no marking or parking lights.

4 ways act like they want to work and make 1 light click, but never come on. EDIT: I just changed the flasher and the 4 ways work. Thank goodness for small fixes there.

Turn signals, brake lights, dome light and backup lights work.

It seems I have 2 different issues because it seems to me the headlights and parking lights are on 2 different circuits.

I think I will disconnect the headlight harness form the fuse box to see if that does anything. If the highlight switch stops clicking that would eliminate a short in the headlight harness, right?

Other than that, I'm out of ideas. 

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If you disconnect the headlight harness from the underdash, you'll have no power to the underdash.

The problem appears to be a grounding issue with the front turn signal/market lamps.

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You're right. I disconnected the harness and no power anywhere. The clicking stopped and I had thought I had troubleshot it to the headlight harness. Took me a minute to realize I had no power, lol.

Turns out I'm my own worst enemy. I disassembled the car probably 10 years ago (man time flies) and replaced both trunk floors, part of the front trunk floor, the taillight panel and taillight brace. Then about 2-3 years ago I installed an EFI Fuel Tank Kit from Tanks Inc. When I installed the ground for the fuel pump, I used the existing ground on the trunk lock brace and soldered the taillight ground and fuel pump ground combining all the grounds. Fast forward to the other day and I ran into the flickering problem. With the Midlife's help on here and my 2 sons help (who just happened to be in town) we traced the problem to the trunk taillights. Turns out when I soldered the ground wires together, I also soldered the License Plate Light power wire in with the grounds. It's a black wire and I mistook it for a ground wire, DOH! We disconnected that wire, which eliminated the flickering and all marker lights and taillights work. YAY!

Thinking back, I can't ever remember having a License Plate Light or ever disconnecting the wire from a light. I think the PO had disconnected that power wire and had it taped up the inside the taillight harness. When I disassembled everything, I didn't notice the wire at the time until I ran across it installing the fuel pump and thought it was a ground.

So, it's huge relief solving that issue and I'm sure in a few months I'll be able to laugh about my mistake.

So thanks for all the help, especially Midlife. You are a huge benefit to the forum.

 

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