98 jeep wrangler headlights wont turn on

Ive changed the relay and the headlight switch on the dash .. still wont turn off headlights ? Just changing parts won't fix it , need to test . Hooking up a professional scan tool , one that can read codes in the BCM - body control module is the way to start to find the problem . Then familiarize yourself with how they work.

Headlamps
Major components of this system are the body control module (BCM), headlamp relay, beam select relay, ambient light sensor, headlamp and panel dimmer switch, turn signal/multifunction switch, park brake switch, and the low and high beam headlamps.
The headlamps may be turned ON in 2 different ways. First, when the driver places the headlamp switch in the ON position, normal operation occurs. Second, when the headlamp switch is placed in the AUTO position, automatic lamp control (ALC) operation occurs. During ALC control, the headlamps will be OFF in daylight conditions or in low/high beam operation in low light conditions.
The headlamp relay receives battery positive voltage directly from the battery. The BCM supplies a ground signal to the headlamp relay for normal headlight operation. The BCM also supplies voltage to the beam select relay coil for high beam headlight operation. When the driver places the headlamp switch in the ON position and the dimmer switch is in the low beam position, the headlamp relay supplies current flow through the left and right low beam headlamp fuses to both low and high beam headlamps. Both low beam headlights are grounded through the beam select relay. When activated, the dimmer switch sends a ground signal to the BCM in the high beam position and a momentary ground signal in the flash-to-pass (FTP) position from G106. The BCM then energizes the beam select relay which switches the headlamp grounds from the low beam headlight bulbs to the high beam headlight bulbs illuminating the high beam headlights. With the headlights in the low beam position, the high beams may be momentarily turned ON or flashed by activating the FTP portion of the switch.
The instrument panel cluster (IPC) illuminates the high beam indicator when the BCM detects that the high beams are requested. The IPC receives a class 2 message from the BCM requesting illumination.
The Headlamps On at Exit and Perimeter Lighting modes can be adjusted using the steering wheel controls to select the function as displayed in the driver information center (DIC). The Headlamps On at Exit selection will allow the driver to customize the period of time that the headlamps remain illuminated upon exiting the vehicle. This period can be adjusted from 0-180 seconds. The Perimeter Lighting feature allows the driver to select if they want the headlamps and backup lamps to illuminate when the door UNLOCK button on the key fob is activated. This feature can be turned ON or OFF by using the DIC steering wheel control buttons.

DTC B2575 Headlamp Control Circuit

Circuit Description
When the body control module (BCM) senses a request for headlamp or daytime running lamp (DRL) illumination, the BCM sends a ground signal to the headlamp relay through the low beam headlamp relay control circuit. The headlamp relay will illuminate the low beam headlamps.

Install a scan tool.
Turn ON the ignition, with the engine OFF.
With a scan tool, command the headlamps ON and OFF.
Does the headlamp relay turn ON and OFF with each command?

Do you know what bi-directional control means ? Need a professional scan tool to do these type of test .

DTC B2602: Daytime Running Lamp Control Circuit Low or Open
DTC B2603: Daytime Running Lamp Control Circuit High

Without this type of info. from service repair manual an using a scan tool your missing the big picture .

Do you know anything about automotive electronics ? Electronic control modules .
Headlamp ON/OFF control is determined by the body control module (BCM) by a signal on the headlamp switch on input circuit when the headlamp switch is in the HEAD position. When the headlamp switch is in the AUTO position, the BCM determines headlamps ON/OFF by the voltage from the ambient light sensor.
If the headlight switch is left in the ON position, the inadvertent power control feature will turn OFF the headlights approximately 10 minutes after the ignition switch is turned to the OFF position. If the driver places the headlight switch in the ON position after the ignition switch has been turned OFF, or if the ignition switch is in the ACCY position, the headlights will remain ON until turned OFF or the battery runs dead.
The high beam indicator is illuminated when the instrument cluster receives a GMLAN serial data message from the BCM that the high beams are illuminated.
High Beams
The high beam headlamps receive voltage from the headlamp high relay located in the underhood fuse block. The BCM controls the relay on the headlamp high beam relay control circuit. High beam control is determined by a signal on the headlamp dimmer switch signal circuit from the multifunction switch. When the headlamp dimmer switch signal circuit is grounded, the BCM grounds the headlamp high beam relay control circuit, illuminating the high beam headlamps. The right and left high beam circuits are independent and are fused independently in the underhood fuse block.
Low Beams - Standard
The low beam headlamps receive voltage from the headlamp low beam relay located in the underhood fuse block. The BCM controls the relay on the headlamp low beam relay control circuit. Low beam control is determined by a signal on the headlamp dimmer switch signal circuit from the multifunction switch. When the headlamp dimmer switch signal circuit is open, the BCM grounds the headlamp low beam relay control circuit, illuminating the low beam headlamps. The right and left low beam circuits are independent are fused independently in the underhood fuse block.

Hooking up a factory scan tool an checking DTC'S - diagnostic trouble codes would be the very first step in trouble shooting this problem .
DTC B257A 00: Headlamp Switch Input Signal Mismatch
DTC 2575 00: Headlamp Control Circuit

I don't believe there is a fuse. There is a circuit breaker built into the headlight switch. If you are sure the headlight switch is good, it could be a bad dimmer switch. If you have a voltmeter, with the headlight switch turned on, a larger yellow wire going from the headlight switch to the dimmer switch should be a hot wire. The dimmer switch sends power on a tan wire to the low beams, and through a light green wire to the high beam bulbs.
If your high beam indicator on the dash also doesn't work, then it is likely one of those switches. A voltmeter or test light would need to be used to find which one is bad. If you can find the connector at the steering column going to the dimmer switch, pull it apart and check for power on the yellow wire coming from the headlight switch, with the headlight switch turned on. If no power, the headlight switch is bad. If there is power there, then the dimmer switch must be bad.

The headlight switch gets power for the headlights from a 50amp fuse.
The fuse powers the headlight switch then the dimmer switch breaks for high and low beams. So if the high beams work, the problem may be with the dimmer switch.
The dimmer switch is made into the turn signal switch on the column. You would need to check the low and high beam circuits at the switch for power.

CHECK HEADLIGHT FUSE OR CIRCUIT BREAKER IF ALL IS GOOD.YOU COULD HAVE FAULTY HEADLIGHT SWITCH OR FAULTY DIMMER SWITCH.

Replace the dimmer switch.

alot of vehicles have a seperate fuse and/or relay for the high and low beams. if you can't find a problem there it could be the swich itself.

https://s12.postimg.org/6o2zcv3hp/jetta_headlamps.jpg

Click on the link.
This is for 03 jetta gls
There are fuses for left and right low beams. Headlights on low beam, use a test light, see if voltage on fuse circuit? If no voltage that will lead us back to dimmer switch or problem with wiring circuit from dimmer switch.

Ckeck the headlight connections they are notorious for corroding. Check the ground connection for the lights. Pull your dimmer switch back as if you were flashing a car to pass and see if they work there. If they do you have a dimmer switch problem.

There are no relays for the headlights. Your problem could be from the headlight switch. You would have to check and see if you have power coming out of the switch on the low beam side. Check with a test light.