I have a 1998 Nissan Altima. My headlights won't turn on, but my parking lights and tail lights won't turn off unless I unhook my battery. Any ideas what the problem might be? Or a solution?
The first place to look for the headlights would be the fuse panel(s). Often there are two: one inside the passenger compartment, either at the driver or passenger kick panel or on the side of the dash where the door covers the dash on the driver side. The other is the engine compartment (in a black plastic box--diagram will be on the inside cover or on the internet). Next check the headlight relay(s). These are usually (but not always) in the engine compartment in a black plastic box.
If the fuses are okay, the relays are easily checked by finding an identical # relay in the box that you know is working (sometimes the horn relay is a good one to try) and swap it into the position you want to test, then test it.
For the lights that are staying on, there could be a ground in the switch stalk that is keeping a relay energized (yech ... replacement stalks are not cheap and can be a pain, especially if you have air bags), or the relay could have failed in the "on" position. If you pull that relay, the lights should go off. Again, swap it with a good relay and if the lights come on again, you know the problem is in the switch wiring. If they don't come on, you know the old relay was bad.
Let us know what happens.