1987 FC NA headlights wont turn on
 

So when I bought the car I was given a new light switch and was told that it was the reason the headlights didnt turn on. So I installed a new light switch and still no headlights. The brights icon on the dash doesn't show up either. I also just installed an aftermarket radio if that makes a difference. Need some help on why they wouldn't work.

headlight fuse Ok in the engine bay fuse block?

Doesn't look like its popped but wouldn't hurt to change.

I have changed the fuse and still nothing.

When you gain access to the headlight switch you should notice that the Red wire in the plug should have constant voltage (no key necessary). The White/Green wire should also have constant voltage. If both of these wires check out then turn the knob to the first position and the Red/Black wire (powers the tail lights) and the Red/Green wire (powers the dash lights) should now have voltage to them. W/the switch turned to the second position the White/Blue wire should have a ground to it (very low voltage).

Alright I will take that all apart and check that voltage

So I finally got to borrow a multimeter and all the wires checked out, what's next?

In front of the radiator are a series of relays. One of these relays is the Headlight Relay. It has four wires, two of them are Red, one is Red/Green and the fourth wire is White/Blue. Test either of the Red wires for constant voltage (no key) as they should have 12 volts and if not then the Head fuse is likely blown. If the Red wires have voltage then ground the White/Blue wire and the lights should turn on ( not up, but on).

Alrighty ill check that sometime tomorrow and let you know what happens!

If you ground the White/Blue wire do so when the relay is plugged in as opposed to unplugged.

Dumb question but how exactly do I ground the wire then?

Slide the ground wire into the back of the plug where the White/Blue wire resides.

So I just checked and all wires checked out but no lights.

Attachment 493447



Attachment 493448

I was gonna ask are the relays supposed to be bolted somewhere in particular and do those little blue wires have anything to do with it?

When you ground the White/Blue wire (while plugged in, and a good ground source for the ground wire should be either the negative battery terminal or the alternator) the relay should pass voltage from one of the Red wires to the Red/Green wire so this is the next thing to check. If there is no voltage on the R/G wire when the White/Blue wire is grounded (and Red wire has constant voltage) then the relay is no good. If you place voltage to the R/G wire the lights should come on assuming the bulbs and the Dimmer Relay (another relay) are working properly.

Those Blue wires in the 2nd pic are not relevant to your problem.

Do you think this rust and corrosion on the relay is the problem?

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Attachment 493458

And I did check all the relay wiring after cleaning up the relay and everything checked out.

So the Red/Green wire has voltage w/the White/Blue wire grounded?

Yes.

I was supposed to put the black from the multimeter to the white blue and red to the red green correct?

The R/G wire runs to the Dimmer Relay, which should be next or close to the Headlight Relay. Does the R/G wire in its plug have voltage, and if so, how much voltage is it reading? If it has 12 volts or so then the Red/Black wire in the plug should then have voltage. Does it?

Where did you get this from? The ground wire is a wire which has but two ends. One end goes to the back of the White/Blue wire and the other end to a ground source. This should cause voltage to be found on the Red/Green wire. Using the multimeter set to DC volts the Red meter lead is placed to the R/G wire and the Black meter lead set to a ground such as the battery negative terminal. Should cause the meter to read 12 volts.

I'm sorry I'm not to savy with car wiring haha. But i don't get the ground wire source, I get that you say the white blue is the ground but I don't know where the other end would lead. I get 12 volts on the two red.

You take a piece of wire you have laying around. A wire long enough to be shoved into the back of the White/Blue wire on one end and the other end placed on the negative battery terminal. When this is done it should cause the lights to turn on. Meaning it causes the R/G wire to have voltage.

Well that made a lot more sense! I didn't get any voltage from it.

If the White/Blue wire was properly grounded and the R/G wire failed to show 12 volts then the relay is likely your problem. If you take the wire used as a ground wire and jumpered voltage from one of the Red wires to the R/G wire then the lights should turn on. If they do then this proves that the relay is damaged or the grounding technique performed on the White/Blue wire was faulty.

Jumpering is basically the same thing as the grounding of the White/Blue wire. One end of the wire goes to a Red wire in the plug and the other end goes to the R/G wire and should cause the lights to turn on.