Headlights Not Working!

dolfan87 · Nov 22, 2006

Hey all,

It's been forever since I posted in here, and I apologize for my dissapearing act. My band has taken over my life, and the mach sat in the garage for the last 8 months or so.

Anyway, we had a break in our schedule, and I started working on the car a lot. I had the exhaust installed today, and actually drove her for the very first time. It was really exciting.

This will be (I am sure) the first of MANY questions I will be asking.

I have a brand new wiring harness (from the fuse box forward to the lights), new headlight switch, and new headlights. All stock stuff. My dash lights all work, as do the interior lights. However, nothing happens when I turn on the headlights...save for the passenger lower turn signal light comes on.

Any ideas of where to start? All the fuses are brand new.

Now I realize I am going to have a ton of gremlins (like the fact that my professionally built 393 leaks from the rear main...special) but I wanted to start with this.

I haven't had a chance to really test the suspension, and I will post pics as soon as I can get a few decent shots.

Peace

Gram

bnickel · Nov 22, 2006

there is a ground wire that attaches to the lower metal dash right above the headlight switch, do you know for sure that it's installed? i had a similar problem until i figured out the ground wire issue. also there is another ground right under the gas pedal, at least on my car, that is the main ground for the underdash harness. it definitely sounds like a ground issue to me.

dolfan87 · Nov 22, 2006

I will check that out...thanks!

dolfan87 · Nov 23, 2006

Ok update.

Turns out the headlight high beam/low beam switch was not plugged in. Now both the lights come on in the high beam position, but only the passenger light comes on in the low position.

It is a brand new switch.

Another odd thing, the drivers side marker lights do not come on with the headlight switch. I took the lower valance light out , removed the lens, and checked to see if I had power, and I do. Replaced the bulb twice, still nothing. So I used the actual ground in the light socket, and checked again for power...none.

So when I use my test light grounded to the body, I have power. So this tells me that there is a ground issue only on the drivers side.

Any ideas?

bnickel · Nov 23, 2006

dolfan87 said:
Ok update.

Turns out the headlight high beam/low beam switch was not plugged in. Now both the lights come on in the high beam position, but only the passenger light comes on in the low position.

It is a brand new switch.

Another odd thing, the drivers side marker lights do not come on with the headlight switch. I took the lower valance light out , removed the lens, and checked to see if I had power, and I do. Replaced the bulb twice, still nothing. So I used the actual ground in the light socket, and checked again for power...none.

So when I use my test light grounded to the body, I have power. So this tells me that there is a ground issue only on the drivers side.

Any ideas?

i'd still check both of those grounds i mentioned earlier. i couldn't get any of my lights except the brake lights to work without them hooked up right.

Tim65GT · Nov 23, 2006

There should be a ground lug with two black wires screwed to the radiator support near or with the voltage regulator.

You didn't say the parking lights are new. Age and heat from current makes the little springs behind the contacts weak. Voltage checks ok with a meter probe, but when the bulb is in, they might not reach the contacts on the bulb.

As far as the low beam, check the red black wire that goes from the driver side Headlamp plug to the pass side headlamp plug.

dolfan87 · Nov 23, 2006

Bryan- Both grounds are clean and solid.

Tim- I have a one wire, self regulating alternator, and I did away with the external reg and wiring. This has me now wondering if I also did away with an inportant ground wire.

I have the ground on the rad. support by the horn wires hooked up, but now that I think about it, the voltage regulator did have a ground wire too.

Crapola.

Here is another tid bit. The blinkers work on the drivers side when the headlights are off. Turn on the headlights and natta. Also my tach is hooked up properly and it's not working either.

Oh I could go on and on...

Happy Thanksgiving you guys!!

Tim65GT · Nov 23, 2006

This has me now wondering if I also did away with an inportant ground wire.

Here is another tid bit. The blinkers work on the drivers side when the headlights are off. Turn on the headlights and natta. Also my tach is hooked up properly and it's not working either.

The head light element is the path to ground for the turn signal when turmed off. This further points to the ground you may have don away with.

Welcome back to the hobby and Happy Thanksgiving to you!

dolfan87 · Nov 23, 2006

I have been looking through my wiring schematic, and I have all grounds in tact. The schematic does not show the path to ground for the lower valance driving lights, nor the side marker lights.

It does not appear to be connected to the headlights in any way.

I don't have the rear lights hooked up, or grounded, and I am wondering if that is an issue.

dolfan87 · Nov 23, 2006

Ok, I have been out there all day. Grounded the rear light harness, and that did nothing. Found out that the low beam filiment on the drivers headlight is toast, and tha's why I don't have low beam on the drivers side.

If anyone has the wiring schematic for the 70 mustangs, can you look and tell me where the heck the marker/turn signal lights ground at? I am following it, and finding nothing.

bnickel · Nov 23, 2006

i wish i had the wiring diagram to help you out. sorry bro, i do know that the 69 and 70 front turn signals ground differently. also, are you talking about the side marker lights or the turn signals under the valance? if it's the signal lights under the valance they do not come on with the headlights only in the parking light mode with the taillights only. hope that helps.

dolfan87 · Nov 23, 2006

Both the side marker and the valance light. It's interesting that you say the valance lights don't come on with the headlights. The passenger side valance light IS on with the headlight, while the drivers side doesn't come on at all with the headlight switch.

This whole thing is messed up. Just a few minutes ago, with the headlights on, and the key off, I hit the turn signal lever onto the passenger side, and the marker lights came on!

geeez...I hate wiring.

bnickel · Nov 23, 2006

oh man, that's sounds like a big can of worms. i'm out of ideas bro. do you still have the old light switch? if so plug it in and see what happens at least remove the switch from the list.

Tim65GT · Nov 23, 2006

For some reason I thought you had a '67.

As the schematic shows, there is only one ground point on the '70 where all the black wires come together.

I'm not familiar with the '70, but maybe the diagrams will help.

http://i50.photobucket.com/albums/f315/Tim65GT/Misc/70MUST.jpg

http://i50.photobucket.com/albums/f315/Tim65GT/Misc/70MUST2.jpg

dolfan87 · Nov 23, 2006

I have the same schematic...thus my frustration.

I am about to start tearing open that new wiring harness.

dennis112 · Nov 24, 2006

If you have an ohm meter, you could verify each wire in relationship to the terminal found at the firewall's bulk head connector. Compare that to the schematic that you have.

It is a slow process, but it works.

I wish the schematic that Tim posted was a little clearer. I would help if the colors of the wires was legible. Hopefully your copy is clearer.

You can get a cheapy volt/ohm meter for around $15 at most any hardware store, Walmart, autoparts store, etc.

dolfan87 · Nov 24, 2006

Thanks guys, I will keep working on it.

dolfan87 · Nov 24, 2006

Would the dash panel plug (the one that goes to the printed board) being unplugged screw anything up? I am using custom guages, and didn't need the plug.

bnickel · Nov 24, 2006

dolfan87 said:
Would the dash panel plug (the one that goes to the printed board) being unplugged screw anything up? I am using custom guages, and didn't need the plug.

did you tap into the turn signal wires from that connector? pretty sure those have to be used for the signals to work unless you completely bypassed them and also the high beam indicator may have to be connected as well.

dolfan87 · Nov 24, 2006

Ok, I finally just unscrewed the fuse box from the plug that goes into the engine bay. I used my test light, and everything that is happening up front is still happening AT the fuse box itself.

Passenger side blinkers work with the lights on or off, but the drivers side blinkers only work when the lights are off. Turn on the lights, and it's a solid "on" light with the test light, but nothing at the actual light when the fuse box is connected to the harness.

So I head out to the actual lights, ground my test light to the bumper, and hit the terminals in the light socket and I get power. But when I use the ground in the light socket itself, and test for power, there is nothing.

There are two wires coming in to the marker lights. One is green and white, and one is black and yellow. Is one of them a ground, or is one for the turn signals, and one for the running lights?

I am about to blow my car up I am so pissed off. Spent two entire days fighting this crap.

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