1987 FC NA headlights wont turn on
03-07-13, 11:19 AM
#1
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.
03-08-13, 10:13 AM
#5
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 **** 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).
Last edited by satch; 03-08-13 at 10:26 AM.
03-19-13, 10:21 PM
#7
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 **** 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).
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03-19-13, 11:16 PM
#8
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).
03-20-13, 01:00 PM
#14
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.
Those Blue wires in the 2nd pic are not relevant to your problem.
03-20-13, 04:36 PM
#20
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?
03-20-13, 04:37 PM
#21
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.
Last edited by satch; 03-20-13 at 04:40 PM.
03-20-13, 05:18 PM
#23
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.
Last edited by satch; 03-20-13 at 05:24 PM.
03-20-13, 05:45 PM
#25
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.
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.