Low Beams not working

If you have already replaced the switch and checked the connections, there could be a few other possible reasons for the low beams not working:

1. Relay issue: The headlight relay controls the low beams. Check if the relay is functioning properly, if not, replace it.
2. Fuse issue: Check if the headlight fuse is blown, if so, replace it.
3. Wiring issue: There may be a problem with the wiring between the switch, relay and lights. Inspect the wiring for any damage, such as frayed wires, loose connections, or melted insulation.
4. Ground problem: Make sure that the ground connection to the headlight is secure.
5. Light bulb problem: Finally, check if the low beam light bulbs themselves are functioning.

If these checks do not solve the problem, it may be necessary to take your truck to a professional mechanic for further diagnosis and repair.

I DON'T KNOW. $1000 ASSEMBLIES ARE PROFIT MAKERS FOR DEALERS. I THINK ASSEMBLIES ARE JUST PLASTIC LIGHT SHADES AND NOT RELATED.
VISUALLY COMPARE PART NUMBER OR LOOK OF OLD BULBS WITH NEW BULBS. CHECK WITH CAR MANUAL.
WHAT IF THE LIGHT SWITCH OR RELAYS ARE FAULTY.?
AT NIGHT LOOK AT RUNNING LIGHTS. HAVE SOMEONE TURN ON LOW BEAMS.THEN HIGH BEAMS TO BE SURE.
YOU HAVE 3 LIGHT LEVELS. YOUR RUNNING LIGHTS AND HIGH BEAMS ARE WORKING BUT NOT YOUR LOW BEAMS. LOOK IN YOUR OWNERS MANUAL FOR THE HEAD LIGHT FUSES AND OR RELAYS TO SEE IF THERE ARE SEPARATE ONES FOR HIGH AND LOW BEAMS.

Either the switch or bad wire connections at the bulbs. Scratch that - I'd be lookin at the switch.

low beam bulb quit

If the bulbs flash when you unlock the vehicle, then they are likely not the issue. My guess is the relay contacts are dirty. Just because a relay clicks, it doesn't mean that it is passing current through the contacts. Try and swap the relay with another of the exact same part number. There's usually another available...ie the horn relay, fog lamp etc..

Shannon, you did not state if you checked for voltage at the fuse location-or better yet at the bulb location-
If a connection at the relay that feeds power to the low beams has come loose, then the low beams will stay out. Suggest that you locate the headlight relay (in a box under the hood) and verify that it is operating. If an assistant can operate the headlights while you listen (and feel) for relay operation, then you can eliminate that as an issue. Next would be the output of the relay (contacts could be bad) - and if you cannot open the relay to verify good contacts, then purchase a replacement relay (possibly from a junkyard) and plug that in.

Remember, the relay supplies the power to the headlights.
-Jim

If high beams work and low beams do not, then it is probably the high/low relay. It is part number 15016745 and has four prongs. To test if your relay has gone bad locate the relay in your fuse box. There will be two of these relays located next to each other. One controls the low beam headlights and the other the cooling fan. Swap the relays and check your low beam headlights. If the low beams work you have a bad 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?

did you check for a relay in your fuse panel? there should be a relay that controls your low beams and one for your high beams. check for that and then if high beams are working swap it with low beam relay. if your problem switches to low beams working and high beams not working replace the bad relay.

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