I have changed the headlight switch, dimmer turn signal, fuse, bulbs and still can not get the low beams working. it will turn on hi beams for passing but will not stay on either. turn signals, running lights, tail lights, and dash lights all work but not headlights. please help
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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.
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.
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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.