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Do you know how to do voltage drop testing ? Leave the blubs in there sockets turn the low beams on , measure voltage on the power side , LH low beam yellow with black stripe an for the RH low beam dark blue wire . If you have battery voltage there, power side is good . Then check ground side both are yellow wires , test with lights on . if you see 6 volts , 12 volts .anything more then .03 millivolts you have a ground side problem . The lights ground through the light switch .
Voltage to the headlamp switch is available at all times from the HDLP SW fuse 7 through CKT 1940 (ORN). When the headlamp switch is turned to the HDLP position, the headlamp power relay coil is energized through CKT 352 (WHT). A signal is also sent to the body control module (BCM) that the headlamp switch is ON. When the headlamp switch is in the AUTO or PARK position, the ambient light sensor (located in the right speaker grill) senses either daylight or darkness and sends the signal to the BCM. When the Ambient Light Sensor detects a dark condition, the BCM produces a signal that will energize the headlamp power relay through CKT 352. The relay coil is grounded through terminal F7 connector 2 of the underhood fuse block to CKT 350 (BLK) to G102. When the headlamp power relay is energized the relay supplies power to the LT HDLP and RT HDLP fuses. The RH low beam headlamp receives current through CKT 198 (DK BLU) from the RT HDLP fuse. The LH low beam headlamp receives current through CKT 712 (YEL/BLK) from the LT HDLP fuse. Both headlamp low beam bulbs are grounded by CKT 524 (PPL) through the underhood fuse block to the multifunction switch (low position) contacts through CKT 10 (YEL) to the headlamp grounding relay in the body relay block through the normally closed contacts to CKT 1850 (BLK) to G200.
likely the dimming relay bad follow wires back to a small box (relay) with connections. Most likely not working properly an needs to be replaced, otherwise the connection from diming switch on stearing column is bad or the switch is bad or the wire from this switch to the dimming relay is bad. you may be able to jumper from the battery to the relay to see if the relay is ok. it is known as a flipflop switch so momentary power causes the relay change position from high to low beam and back.
It shouldn't be the high/low beam switch, as that switches the high/low beam relays. One high beam relay supplies power for both sides, one for low beam, both sides. If you were to lose switch function or a relay, you would lose the high beams or the low beams, but not for just one side. It would be interesting to probe the fuses with a test light and see if you're getting power to and through them. If you are, the problem would be between the fuse box and the headlight, if your not getting power to the left head light fuses, the problem will be in the fuse box. Good luck!
The standard lights are quite good enough if the reflectors and lens are really shiny and not partially rusted. Large bulbs run the risk of melting the plastic reflectors costing new head lights. Adjusting the head lights to correct beam height will also help. You can use relays in the system. Disconnect the wires to the back of the bulbs and attach then to the trigger pins of the relay (4 relays-2 high beam L+R and 2LBeam L+R). Run fused power wires from the battery to the power pin of the relay and out to the beam pin of the bulb. earth the bulbs as normal. The operation works like this You switch on the lights to low beam and the power from the switch energises the relay and drops in the contacts which allows power from the battery ,through the bulb low beam to earth. Switching to high beam energises the relay and allows power from the battery through the relay and out to the high beam part of the bulb through to earth. You have full 12 volts to the lights and reduced current through the light switch. 4 relays --1 each for each light low and 1 each for each light high. jump the wire from each beam position between relays of the same light so that they work off the one wire from the switch
The high and low beam lights use the same power source, so if the low beams work the high beams have power. There is a low and high beam relay controlled by the dimmer switch. If the low beams work and the high beams don't, and the bulbs are good, check the dimmer switch and the high beam relay.
I'm having the same problem right now. I replaced the bulbs still didn't work. Checked all fuses and they were all good. Replaced the relay and they worked for about 20 mins. What could be causing the relay to go bad so fast or whatever?
Power flows from the battery to the main fuse. Then it flows to the control coil and contact side of the headlight relay. When you turn on the headlights, the headlight switch provides ground to the control coil in the headlight relay and that operates the contacts. The contacts allow power to flow to the right and left hand headlight fuses. Power flows to the headlights. The headlight switch is what provides ground to the high and low beams on the headlights.
To diagnose, remove the headlight relay. Using a voltmeter, check for battery voltage on terminals 3 & 4 in the socket with the key in the RUN position. Then turn on the low beams. Test for good ground on terminal 1 in the socket. If you're not getting ground, then you've got a problem with either a bad headlight combo switch or a bad ground. If you get good ground on terminal 1, reinstall the relay, turn on the low beams and test for power in the headlight sockets. If you get battery voltage, that confirms you've got good fuses and wiring up to that point. Next, check for good low beam ground on the red/green wire in the bulb socket. If you're not getting good ground, it's either a bad combo switch or bad ground from the combo switch. Then turn on the high beams and check for good ground on the red/yellow wire in the bulb sockets.
It wouldn't hurt to clean the ID ground on the left side of the instrument panel, but based on everything you've said so far, this sounds like a bad combo switch