mustang35

I'm having trouble figuring out why I have no headlights. I have no power running to the headlight connector under the hood. I've changed the headlight switch and wire harness. The harness had some melting to it. I even changed the combo switch (turn signal). All fuses are fine and the headlights themselves are working when I tested them unplugged from the car. Anybody have any ideas?

petrock

I have the '98 electrical diagnostic manual. The lighting circuit is fairly simple and yours should be very similar if not the same as mine, so it shouldn't be too hard to track down. Couple questions that will help narrow things down:

- Are you not getting power in both head lights?
- What about ground (the black wire) at each connector?
- Do you get power for high beams, but not low beams or vise versa?
- Do you get power for high beams if you flick the multi-function lever back towards yourself, putting it into "pass" mode?

With those questions answered, I can help point you in the right direction. As my dad always said, its simpler/better/cheaper to troubleshoot a problem then it is to just throw parts/money at it. Good luck...

mustang35

Thanks for the reply. I'm not getting power to either headlight, high beams won't come on when you pull back on the multi-function switch. All ground wires that I can find have a good connection and there is no power for either the high beam or low beam.

petrock

How are you checking for power? Are you using a multi-meter, volt-meter or test light?

The ground connection is only half of it. It could be properly connected to the nearest ground, but if there is a break somewhere in the ground wire you won't have ground. One way to check for ground is to use a multi-meter to check for continuity between the ground wire at the light bulb connector and the negative battery terminal. If there is no continuity, then there is no ground connection and the circuit will not be complete and your lights won't work.

When you pull back on the multi-function switch, did the high beam indicator light turn on in the dashboard?

mustang35

I'm testing the connection using a test light grounded on the battery. The high beam light does not come one when I pull back on the multi-function switch.

petrock

Cool. You can verify your getting ground at the headlight bulb by connecting the test light to the positive terminal on the battery and then poking the black wire in the headlight bulb with the test light. Does the test light light up when you do that? If not, you don't have ground and theres your problem.


If by "high beam light" you mean the indicator light in the dashboard/instrument cluster, then cool. That tells me that the problem is up stream of the headlight bulbs.

With the ignition in the ON position (but don't start the car):
- Are you getting power at the Dark Blue & Black wire going into the multi-function switch?
- With the main headlight switch in the "Head" position, are you getting power at the Red & Yellow wire at the multi-function switch?
- With the main headlight switch in the "Head" position, are you getting power at the Red & Black wire at the multi-function switch?
- When you pull the multi-function switch back into pass mode, are you getting power at the light green & black wire at the multi-function switch?
- When you push the multi-function switch forward into high beam mode, are you getting power at the light green & black wire at the multi-function switch?

mustang35

I haven't check these with a tester yet. I try everything out tomorrow when I have daylight to work with. Thanks for the help and I'll let you know what I find.

mustang35

Well I finally figured out my headlight issue. I took the car in to a shop and after 4 1/2 hours they found the problem and fixed it. Turns out the wire to the headlights was corosion on it in a couple of spots. One was in the line that runs under the battery tray and the other was at "T" intersect on the inside of the fender. The mecanic said the only way he figured it out was by the wiring diagram he had in the computer in the shop.

petrock

Yup. Probably alldata.com. Very handy. Having the manual (via all data.com or the actual shop manual) is probably the best purchase you can make for your vehicle. Will pay for itself after the first oil change (or this job alone).

Good to hear you got it fixed...